CITY OF PHOENIX CITYWIDE POINT-OF-USE WATER SOFTENER AND TREATMENT STUDY

Transcription

1 CITY OF PHOENIX CITYWIDE POINT-OF-USE WATER SOFTENER AND TREATMENT STUDY Final Report, First Draft January 14, 2009 Project No: and Contract No: HDR Project Number: E. Camelback Road Suite 350 Phoenix, AZ Phone: Fax: Web: hdrinc.com

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3 Table of Contents 1 Executive Summary Preface Background TDS Contributions to the Wastewater System TDS Goals for Reuse Alternatives to Water Softening TDS Control Programs in Other Communities Drivers Discharge to Septic Tanks Discharge to Sewer Systems TDS Reduction Program Options Considerations Public Education Standards Alternative Technologies Equipment Upgrades Pretreatment Limits Rebates Bans Recommendations References TDS Contribution Estimates Description Previous Studies AwwaRF Study AwwaRF Study Phoenix Case Study TNT Technologies CCWRP Salinity Study Feb, Santa Clarita Valley Joint Sewage Salinity Source Report Estimating Residential Sources of Salts Residential Use of Water Softeners in Phoenix Homebuilder survey Water softener provider survey Modeling Assumptions for Residential Water Softening Industrial and Commercial Softening Industrial water softening survey Commercial Softening Estimate of TDS from Water Softeners by Sewershed rd Avenue WWTP st Avenue WWTP Cave Creek WRP Summary Conclusions References TDS Control Programs iii

4 3.1 Description Drivers Methods TDS Control Programs California Discharge to Septic Tanks Discharge to Sewer Systems Salinity Management Program Descriptions Data Gaps Summary and Recommendations References Alternatives to Point-of-Use Water Softening Description Self Regenerating Water Softeners Hardness and TDS Control Standards Alternatives to Ion Exchange Water Softening Thermal Physical Electrical Chemical Pellet Softening Demineralization Other Cathodic Portable Exchange High Efficiency Ion Exchange Table of Alternatives Summary References Potential TDS Reduction Program Components Description Background Current TDS Conditions Desired Future Conditions Methods of Program Evaluation Potential Program Components Public Education Standards Alternative Technologies Equipment Upgrades Pretreatment Limits Rebates Bans Local and State Institutional Framework City of Phoenix Policies and Ordinances State Laws and Regulations iv

5 5.7.3 Guidance from Other Jurisdictions Regulatory and Policy Gaps Recommendations TDS Goals for Reclaimed Water Uses Description Reclaimed Water Quality Existing TDS Goals Phoenix Area Reclaimed Water Uses Maximum TDS Tolerances Agriculture Industrial and Commercial Cooling NPDES Permitted Discharges Environment Groundwater Recharge Turf Irrigation Summary References List of Appendices Appendix A: Regeneration Calculations Appendix B: Homebuilder Survey Appendix C: Water Softener Vendor Survey Appendix D: Industrial Pretreatment Survey Appendix E: Sewershed Figures Appendix F: Executive Summary of 2008 Chloride Source Identification/Reduction, Pollution Prevention, and Public Outreach Plan (Santa Clarita Valley Sanitation District) Appendix G: California Health and Safety Code Section Appendix H: Water Softener Rebate Programs Appendix I: NSF Certified Drinking Water Systems for TDS reduction and or scale control Appendix J: Selected Phoenix Codes and Arizona State Laws and Regulations Appendix K: Example of Grant Application for Rebate Program Appendix L: Public Education Materials Appendix M: Additional Tables List of Tables Table 1.1 Maximum water quality tolerances for Phoenix reclaimed water uses... 7 Table 1.2 Summary of processes used for scale control... 8 Table 2.1 Summary of TDS increase from AwwaRF case studies (AwwaRF, 2006) Table 2.2 Relationship of softener use to TDS increase based on AwwaRF studies (AwwaRF, 2006) Table 2.3 Sampling results for CCWRP case study (AwwaRF, 2006) Table 2.4 Residential locations sampled and estimated softener use based on analytical results Table 2.5 Sampling from SRWS (SCVJSS, 2002) Table 2.6 Indoor water use for average Phoenix residence (Mayer, 1999) Table 2.7 Salt sources and flows from average Phoenix residence v

6 Table 2.8 Softener penetration in Phoenix based on home construction year Table 2.9 Homebuilder survey summary Table 2.10 Water softener vendor survey results Table 2.11 Total number of single-family residences, by age and sewershed Table 2.12 Residences with softeners based on Reclamation survey (2004) Table 2.13 Modeling scenarios for SRWS efficiencies Table 2.14 Commercial scenarios for SRWS efficiencies in the sewersheds Table sewershed TDS and flow Table 2.16 Salt sources for the 23rd Avenue WWTP sewershed Table 2.17 Salt sources for the 91st Avenue WWTP sewershed Table 2.18 Salt sources for the CCWRP sewershed Table 2.19 Salt sources based on alternative modeling assumptions for CCWRP sewershed Table 2.20 Total salt balance for Phoenix sewersheds Table 2.21 Total salt balance for Phoenix using alternative modeling assumptions for CCWRP sewershed Table 2.22 TDS and salts in sewershed without softening Table 4.1 NSF/ANSI standards for hardness Table 4.2 NSF/ANSI standards for TDS Table 4.3 Table of Alternatives Table 4.4 Summary of processes used for scale control Table 5.1 Phoenix Codes reviewed Table 5.2 Review of State laws and regulations Table 6.1 Arizona reclaimed water quality requirements for crops (Metcalf & Eddy, 2007) Table 6.2 Salinity hazard from irrigation water (PNW, 2007) Table 6.3 Chloride tolerances for crops (PNW, 2007) Table 6.4 Reclaimed water specification limits for turf irrigation (AwwaRF, 2006) Table 6.5 Maximum water quality tolerances for Phoenix reclaimed water uses List of Figures Figure 1.1 Sources of salinity to the City of Phoenix sewersheds... 3 Figure 1.2 Salt source, by sewershed... 5 Figure 1.3 Detailed salt sources, by sewershed... 5 Figure 1.4 Effect of softener efficiency on brine TDS Figure 1.5 Regeneration frequency of DIR and time clock controlled SRWS Figure 2.1 Data tables from AwwaRF, Figure 2.2 Regeneration frequency of DIR and time clock controlled SRWS Figure 2.3 Average daily softener TDS based on salt efficiency of softener Figure 2.4 Salts, by source, from residential based on Table Figure 2.5 Salt sources Figure 2.6 Percentage of salts, by source, in 23rd Avenue WWTP sewershed Figure 2.7 Percentage of salts, by source, in 91st Avenue WWTP sewershed Figure 2.8 Percentage of salts by source in CCWRP for both modeling assumptions.. 42 vi

7 Figure 2.9 Phoenix salt sources Figure 2.10 Salt source, by sewershed Figure 2.11 Detailed salt sources, by sewershed Figure 5.1 Effect of softener efficiency on TDS of brine Figure 5.2 Regeneration frequency of time clock SRWS compared with demand initiated regeneration SRWS with the same salt efficiency Figure 5.3 Local limits in mg/l (Industrial Pretreatment Report, 2006) Figure 6.1 Fate of treated wastewater in Phoenix in Figure 6.2 Combined effects of SAR and EC on soil infiltration rate (AwwaRF, 2006) Figure 6.3 WWTP and recharge facilities for Phoenix wastewater (Phoenix, 2008) vii

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9 1 Executive Summary 1.1 Preface The City of Phoenix Water Services Department (City) is concerned about the rising concentration of total dissolved solids (TDS) and associated ions and salts in wastewater collected and received at its water reclamation facilities. TDS and its components have the potential to restrict the beneficial use of reclaimed water, increase the City s water management costs, and decrease economic and environmental sustainability of the region. The City has participated for several years in the Central Arizona Salinity Study (CASS), the Multi-State Salinity Coalition (MSSC), and numerous related initiatives and efforts to understand the sources, impacts, and implications of increasing levels of TDS in its reclaimed water. Point-of-use water treatment systems, particularly home and commercial water softeners, have been identified as a potentially controllable source of TDS. The City retained HDR Engineering, Inc. (HDR), to conduct the study described in this report to gather information necessary for the City to make a decision regarding the implementation of policies to control TDS discharges associated with point-of-use water softening and other treatment systems. This report documents the results of the citywide water softener study. The study was conducted as a series of discrete tasks that were each documented in a Technical Memorandum, which form the other sections of this report: Study Task Task Title Report Section Section Title Task 1 Estimate TDS Contribution Section 2 TDS Contribution Estimates Task 2 Research TDS Control Section 3 TDS Control Programs Programs Task 3 Water Softener Alternatives Section 4 Alternatives to Point-of-Use Water Softening Task 4 Potential TDS Reduction Program Components Section 5 Potential TDS Reduction Program Components Task 8A TDS Goals for Reclaimed Water Uses Section 6 TDS Goals for Reclaimed Water Uses This Executive Summary was developed at the conclusion of the study to synthesize the information developed through each project task. The topics presented in this section do not necessarily follow the order in which the tasks are numbered or the sequence in which the tasks were completed. Rather, it was developed to provide an overview of the study as a whole and is arranged in a logical progression of the information required to generate recommendations for the City to consider in developing its salinity management program. 1 Executive Summary

10 1.2 Background The Phoenix area is known to have very hard water, with levels at grains per gallon (TNT, 2006). Hardness is a component of TDS, and is measured by the amount of calcium and magnesium in the water. One grain of hardness per gallon equals 17.1 milligrams of hardness per liter (mg/l). Hard water causes scaling of pipes and appliances and can affect the taste of water. Most self regenerating water softeners (SRWS) employ ion exchange technology to effectively remove calcium (Ca) and magnesium (Mg) ions in the water. As water flows through a negatively charged resin bed in the SRWS, positively charged Ca and Mg ions are attracted to the resin. The hard ions displace weaker positively charged sodium (Na) or potassium (K) ions from the resin bed that are carried by the water to the point of use. Resins must be regenerated with Na or K ions to create capacity for the continual removal of Mg and Ca ions from source waters. Depending on the SRWS technology, this regeneration may occur at a specific frequency (time clock) or based on the volume of water (demand initiated regeneration [DIR]) that has passed through the resins. Whichever technology is used, the resin is regenerated using a sodium chloride (NaCl) or potassium chloride (KCl) brine solution to flush the resin to replace the Ca and Mg ions with Na or K ions. The wastewater from the regeneration cycle is then discharged directly into the sewer with a very high TDS. Because TDS consists mainly of the positively and negatively charged ions of salts, TDS is also referred to as salinity and the ions are also referred to as salts. Therefore, in the process of reducing hardness of the product water, ion exchange increases TDS in wastewater and the salinity of reclaimed water. The City s water service area has a significant penetration of SRWS, as detailed in this and previous studies. SRWS units collectively represent a potentially controllable source of salinity loading to the City s wastewater systems. The City has three main sewersheds associated with its three wastewater treatment and water reclamation facilities: Cave Creek Water Reclamation Plant (CCWRP), 23rd Avenue Wastewater Treatment Plant (WWTP), and 91st Avenue WWTP (collectively referred to as WWTPs ). The City s wastewater fee structure was developed to support the costs of building, operating, and maintaining WWTPs that employ variations of conventional activated sludge technology, filtration, and disinfection to treat domestic sewage. The targeted parameters of this type of treatment train include total suspended solids (TSS), biological oxygen demand (BOD), nutrients, and pathogenic microorganisms. The fee structure does not support costs associated with advanced treatment to remove TDS or other water quality constituents that can make their way through a conventional WWTP. As depicted on Figure 1.1, each sewershed has a number of sources of salinity including source water, Sub-Regional Operating Group (SROG) city wastewater inflows, and residential, commercial, and industrial activities. 2 Executive Summary

11 SOURCE 650 mg/l TDS 284 MGD Residential Commercial Industrial Other Cities CCWRP 4.4 MGD TDS: 1,121 mg/l 91st Ave WWTP 132 MGD TDS: 1,055 mg/l 23rd Ave WWTP 47.9 MGD TDS: 1,030 mg/l Figure 1.1 Sources of salinity to the City of Phoenix sewersheds To develop an effective salinity management program, the City needs to know where the salts originate, the basis upon which reclaimed water quality goals can be developed, what alternative technologies to ion exchange water softening exist, what other agencies using reclaimed water have done to control TDS, what authority the City has and/or needs to develop to manage salinity, and what data or institutional framework gaps exist. These considerations were addressed in this study to develop the recommendations provided at the conclusion of this report. 1.3 TDS Contributions to the Wastewater System HDR estimated the TDS contribution originating from SRWS within the three sewersheds. Numerous salinity studies completed in Phoenix and elsewhere were reviewed to develop a modeling approach for estimating the percentage of TDS by sewershed that is attributable to SRWS. The model was built using a nonproprietary Microsoft Excel workbook, now owned by the City. The TDS contribution assessment was built on previous research to determine the TDS impact from softening activities without performing additional wastewater monitoring or sampling. Additional surveying of Phoenix homebuilders, water softener vendors, and the industrial sector was performed to develop new data for this study. Based on TDS and flow data for 2007, more than 1.61 million pounds of salt passed through the City s WWTPs. Most of the salts that enter the wastewater system are imported into the region with potable source waters including the Salt River, Verde River, and the Central Arizona Project canal. Phoenix source water contributes approximately 42 percent of the total salts. Other salt sources include other SROG cities 3 Executive Summary

12 and residential, commercial, and industrial activities that result in wastewater discharges to the WWTPs. Using survey data from the United States Bureau of Reclamation (Reclamation) that related water softener use to age of residence, a series of maps and tables were produced identifying locations, age, and water use data for single-family residences in the three sewersheds. Reclamation s penetration estimates were applied to the three sewersheds. Based on this analysis, nearly 31 percent of homes in the City service area are using SRWS. The levels of TDS originating from SRWS are not consistent because many water softener models that are sold and installed have a range of salt and water efficiencies, regeneration controls, and issues associated with operation and maintenance by the owners. Residential Softening Four scenarios were developed to analyze salt loading assuming specific percentages of SRWS salt efficiencies for the sewersheds. Modeling results indicate that residential water softening produces from 4 to 22 percent of total salts in each of the sewersheds. Commercial Softening Salts contributed by commercial softening were estimated using water demand data for restaurants (excluding fast-food restaurants), laundromats, hotels, and car washes. Two scenarios were developed to represent the salt efficiencies of the commercial softening activities. Modeling results indicate that commercial water softening produces from 1 to 4 percent of total salts in each of the sewersheds. Industrial Softening A survey of permit holders in the City s Industrial Pretreatment program indicated that 77 percent of industries are using SRWS for partial softening of the water. Industries discharge 123,883 pounds (lbs) of salts per day to the waste stream. Nearly 17 percent of industrial salts are attributable to industrial SRWS. The remaining salts are attributable to influent from the other SROG cities and other residential, commercial, and industrial discharges. Phoenix wastewater gains, on average, 400 mg/l of TDS in the flow pathway between source waters and the WWTPs. It has been previously estimated that 26 percent of this increase in TDS is attributable to water softener discharges. Based on modeling assumptions, between 137,202 and 160,869 lbs per day of salt are added to Phoenix sewers from water softening activities in the residential, commercial, and industrial sectors. For the entire volume of wastewater being treated at CCWRP, 23rd Avenue WWTP, and 91st Avenue WWTP, this study estimates that 8 to 10 percent of the total salts are attributable to water softening activities from residential, commercial, and industrial activities. Figure 1.2 displays the daily salt load, by source, for each sewershed. 4 Executive Summary

13 500, , ,000 Salt [lb/day] 350, , , , ,000 Residential Com/Indus Source Other Cities 100,000 50,000 0 CCWRP 23rd Ave 91st Ave Sewershed Figure 1.2 Salt source, by sewershed Figure 1.3 displays the salt balance for each of the sewersheds as a percentage of the total. The cross-hatched regions represent salts originating from water softening activities in each of the sectors. Salt [lb/day] 100% 90% 80% 70% 60% 50% 40% 1,733 8,900 9,733 15,870 17,919 42,892 92,499 5,860 19,879 81, , ,467 8,791 Indus Soft Com Soft Res Soft Com/Indus Other Res Other Other Cities Source 30% 20% 23, , ,922 10% 0% CCWRP 23rd Ave 91st Ave Sewershed Figure 1.3 Detailed salt sources, by sewershed There is some uncertainty associated with these estimates because of the number of assumptions required to develop the model. In reality, it is very difficult to project how many softeners are used in the sewershed since there is tremendous variability in efficiencies and operation. It was assumed that the Reclamation survey represented the best data for determining water softener penetration in the sewershed. Modeling results for the 23rd Avenue and 91st Avenue WWTP sewersheds appear to validate the 5 Executive Summary

14 Reclamation water softener penetration values based on age of household. A detailed discussion of the assessment of TDS contributions is provided in Section 2, TDS Contribution Estimates. 1.4 TDS Goals for Reuse The City of Phoenix currently uses the majority of its reclaimed water. As the production and availability of reclaimed water increases with population growth over time, use of reclaimed water in the region will continue to expand to provide a reliable water supply for a wide variety of potential end uses. HDR researched maximum tolerance concentration levels of TDS that have been recommended by previous studies for reclaimed water uses such as groundwater recharge, golf course irrigation, turf irrigation for public areas, and industrial/commercial cooling systems. Elevated TDS concentrations and TDS component concentrations in water can have a negative effect on vegetation and soils, and cause scaling of cooling tower materials. TDS is commonly referred to as salinity and is approximated by the amount of inorganic salts (Ca, Mg, Na, K, chloride, sulfates, and bicarbonates) and organic solutes. Certain constituents of TDS such as Na and chloride can significantly damage plants and soils. Nearly 74 percent of treated wastewater from Phoenix reclamation plants is reused for agricultural irrigation, power generation, habitat restoration, groundwater recharge, and turf irrigation. The balance of the reclaimed water is discharged to the Salt River, some of which is subsequently used for irrigating agriculture. Reclaimed water must be produced and managed such that water quality does not negatively impact human health, crop yields, aquatic species, and industrial and commercial cooling applications. Long-term effects of reclaimed water constituents and requirements for leaching and drainage must be considered when determining water quality requirements. The management of water quality, particularly salts in the system, is important for the sustained use of reclaimed water for each particular end use. Maximum tolerances for TDS depend on the current and future uses of the reclaimed water. For irrigation, the maximum tolerance depends on types of crops or turf being irrigated, season, types of soils, and specific ion concentrations in the reclaimed water. Restrictions on cooling water quality are dependent on the cooling tower materials and required cycles of concentration. Water quality for recharge is site and technology specific. More specifically, it depends on location horizontally and vertically of potable water wells, receiving groundwater quality, the manner in which recharge is accomplished, and the soil adsorption ratio (SAR). Water quality goals for reclaimed water uses should include consideration of TDS and specific ion concentrations to protect all reclaimed uses. On the other hand, the cost associated with producing reclaimed water of adequate quality for all reclaimed water uses may be determined to be too great, and the City may need to determine that certain reclaimed water use opportunities will not be pursued as a matter of policy. There are, of course, other considerations for making such policy determinations, but cost is typically a 6 Executive Summary

15 primary consideration. Table 1.1 summarizes water quality tolerances and identifies the maximum tolerance based on the most sensitive reclaimed water uses. Table 1.1 Maximum water quality tolerances for Phoenix reclaimed water uses Max Tolerance Phoenix Reclaimed Use TDS Sodium Chloride Calcium Magnesium Sulfates Bicarbonates Ammonia Agriculture C C C Industrial/ Commercial Cooling * A control scaling A A 0.2 NPDES B Recharge C C C C Turf A - the Larson-Skold index relating chloride, sulfate to bicarbonate and carbonates less than 0.8 B - limiting factor in the WET test for C. dubia C - Depends on SAR * Maximum for receiving water supply in cooling systems Currently, the TDS in the City s reclaimed water is, on average, less than 1,200 mg/l; however, there is concern about the salinity levels and specific ion concentrations in the reclaimed water as salts continue to increase in the soils and surface waters in the Phoenix area. A major concern for the continued ability to use reclaimed water is the amount of TDS contributed by residential, commercial, and industrial water softening. Increases in Na and chloride concentrations in wastewater will have a negative impact on all current reclaimed water uses in Phoenix. Salinity-related negative impacts are being noted by some of the turf facilities using reclaimed water from CCWRP. 1.5 Alternatives to Water Softening The City asked HDR to research information about alternatives for point-of-use ion exchange water softening systems, which are the most common products used to reduce hardness. Information such as technology employed, manufacturer pricing, water and salt use, energy consumption, and any advantages or disadvantages are summarized in this section and further discussed in Section 4, Alternatives to Point-of-Use Water Softening. There are many products using technologies that may be capable of reducing scaling effects of water hardness. However, there are no accepted U.S. standards for testing the hardness mitigating effects of products that do not use ion exchange, distillation, ultrafiltration, or reverse osmosis. In addition, most water hardness reducing products do not provide sufficient technical data to support advertised claims and are marketed based on testimonials rather than performance data. Additionally, negative results have been reported for some similar products used in industrial applications for controlling scale in cooling structures (Kiester, 2004). Academic research has supported a number of treatment technology processes, but has not clearly defined the parameters for reproducing results at locations with differing water chemistry and flow rates. The only standard that may be applied for evaluating many of these alternative water treatment devices is the German standard DVGW W512. Table 1.2 summarizes the evaluated processes and their effectiveness at removing hardness, TDS reduction, applicable U.S. standards, scale control, and the change in TDS concentrations in water entering the waste stream. Hardness removal refers only to removal of Ca and Mg ions. Some of the processes do not remove any ions, but instead 7 Executive Summary

16 change the water chemistry to prevent the hardness ions from causing scale accumulation on surfaces. Ion exchange and demineralization increase the TDS concentration in the waste stream through the addition of ions. Distillation and pellet softening technologies have the potential to decrease the TDS concentration entering the waste stream because the calcium carbonates and other salts are removed without the addition of other ions. The remaining processes do not change the TDS in the waste stream. Table 1.2 also identifies which processes have National Science Foundation / American National Standards Institute (NSF/ANSI) standards for certifying for TDS or hardness removal. Depressurization and demineralization technologies are not available for residential use. Process Table 1.2 Summary of processes used for scale control Hardness Removal TDS Reduction NSF/ANSI Standard Scale Control Change in TDS to WW Ion exchange 95% only Ca, Mg 44 yes increase Distillation 99% 99% 62 yes decrease Ultrafiltration > 75% > 75% 42 yes neutral Reverse Osmosis > 75% > 75% 58 yes neutral Depressurization 2 NA neutral Magnetic 0% 0% unknown neutral Electromagnetic 0% 0% unknown neutral Electrostatic 0% 0% unknown neutral Electrolysis 0% 0% unknown neutral Capacitive Deionization 99% 99% yes neutral Catalytic Conditioners 1 0% 0% yes neutral Pellet Softening only Ca only Ca yes decrease Demineralization 2 < 50% only Ca NA increase 1 A number of catalytic conditioners have been certified by the German DVGW W 512 standard 2 These processes are not applicable for residential systems In summary, of the many processes described as potential alternatives for ion exchange SRWS for reducing hardness or the scaling effects of hardness, the most reliable are reverse osmosis, ultrafiltration, and distillation. Capacitive deionization and catalytic conditioning, specifically, epitaxial crystallization, are potentially viable alternatives to ion exchange softening; however, additional testing should be performed. A testing method or additional research should be developed to identify the effectiveness of magnetic water treatment for residential hardness control. The technologies of distillation and pellet softening have greatest potential for reducing TDS concentration in wastewater and reclaimed water. 1.6 TDS Control Programs in Other Communities HDR interviewed industry experts and conducted an Internet search to identify states, municipalities, and utilities that have developed information, programs, or policies regarding discharges from SRWS Drivers The two primary drivers for TDS control are water reuse needs and receiving water quality limitations. Depending on the plant variety, it has been reported that turf facilities 8 Executive Summary

17 and agricultural operations in the Phoenix area can use reclaimed water with a TDS concentration at or below 1,200 mg/l with minimal negative effects (CASS Phase I, 2003). Recent informal discussions with local reclaimed water users indicate that the general TDS tolerance level might actually be lower: approximately 1,000 mg/l. Negative impacts have been observed above this concentration and include poor crop performance and the need to use more water to leach accumulated salts from the root zone. In addition to the issues associated with elevated TDS concentrations, high concentrations of Na or chloride ions can negatively affect users of reclaimed water and potentially affect aquatic species in receiving waters. Surface water discharge permit limitations are often designed to protect downstream reuse needs in addition to aquatic life Discharge to Septic Tanks A number of states and local jurisdictions have enacted some form of residential water softener regulations. In most states, the regulations have targeted the discharge of water softener regenerate to on-site septic tanks. Research conducted under this study indicated that three key areas of concern have led to regulations prohibiting SRWS discharges to septic systems: 1) The high salt concentrations in SRWS discharges could be harmful to the biological function of septic tanks. 2) SRWS regeneration discharges increase the hydraulic burden on the septic tank and could alter performance. 3) The salt load of SRWS discharges could alter the soil chemistry of the leach field and negatively affect treatment capacity. Based on these presumptions and the field experience of septic tank installers in many regions, several states have enacted regulations or policies that prohibit the connection of SRWS to on-site septic systems. In most instances, the SRWS discharges are recommended to bypass the septic tank and discharge to a separate drywell. In response to the growing popularity of such regulations, industry representatives commissioned two studies in the late 1970s. The studies were conducted by the National Sanitation Foundation (now NSF International) and the University of Wisconsin- Madison. These studies concluded that no deleterious relationship existed between SRWS discharges and septic tank performance; however, these studies did not put the issue to rest (Bruursema, 2005). The limited scope of these studies and the practical firsthand observations of many septic tank installers contribute to the continuing debate. While many states have regulations that ban the discharge of SRWS regenerate to on-site septic systems, some have reversed their thinking. New Jersey rescinded its ban, and Kentucky decided to hold off on enacting its own ban in the face of pending opposition 9 Executive Summary

18 from the water softener industry (McKenzie, 2005). Of special interest, the State of Pennsylvania Department of Environmental Protection has issued an order that SRWS discharges must go to the treatment tank, not directly to the ground or waters of the State. The debate continues to determine whether SRWS discharges negatively affect septic tank operation. Furthermore, different states have conflicting and/or frequently changing guidance on this issue. Because of the relatively small number of septic tanks present within the City s water service area, the discharge of SRWS brine to septic systems is not a priority issue for the City. In the event that the City or other local jurisdictions wish to pursue this issue as part of their salinity management efforts, further review of the existing studies and perhaps the initiation of new research in the Phoenix metropolitan area would be warranted before any conclusive course of action can be recommended Discharge to Sewer Systems The State of California has the longest and perhaps most controversial history in dealing with water softener regulation for sewer systems. In 1961, Los Angeles County Sanitation Districts No. 26 and No. 32 first adopted resolutions that prohibited the discharge of regeneration brines from SRWS. Debate over the regulation of SRWS has raged in California since this original action, as detailed in the Section 3, TDS Control Programs. At this point, it is difficult for a local jurisdiction to regulate the residential use of water softeners in California. This was most recently evidenced by an action taken by Governor Arnold Schwarzenegger in September 2008, in which he vetoed a bill passed by the state legislature that would have broadened the ability of local jurisdictions to regulate SRWS. A review of California s 20-year history with water softening regulations demonstrates the difficulty in limiting residential water softening through bans. However, limiting industrial water softening typically generates less opposition. One avenue of regulation is the National Pollutant Discharge Elimination System (NPDES) permitting process under the Clean Water Act. NPDES permits protect water quality in receiving surface waters from point and nonpoint pollution sources. The NPDES permit allows utilities to establish local limits to control constituents of concern, including TDS. The NPDES pretreatment program attempts to accomplish the protection of WWTPs and receiving waters through the regulation of industrial sources of discharge. Most utilities operate a pretreatment program, but not all are concerned about TDS. States are also required to adopt surface water quality standards called total maximum daily loads (TMDLs) that protect impaired waterways from specific pollutants. TMDLs determine the total amount of a specific pollutant the waterway can receive while still meeting the water quality standard. In the case of California s Santa Clarita Valley, chloride was the TMDL that drove the salinity management program. The chloride limit for industrial dischargers is either 100 mg/l or an individual limit determined based on technical and economic feasibility. The impacts of increasing salinity on local water resources have become a popular topic of conversation for water managers. Several local- and state-level jurisdictions have taken 10 Executive Summary

19 steps to begin managing salinity impacts. Actions include providing public education, establishing standards, encouraging equipment upgrades, setting NPDES pretreatment limits, offering rebate incentives to reduce saline discharges, and implementing regulatory bans on the use of water softening devices. By far the most common issue that has been dealt with nationwide is the discharge of brine to on-site septic systems. However, increasing attention has recently been paid to industrial, commercial, and residential discharges to sewer systems containing high concentrations of TDS. 1.7 TDS Reduction Program Options Descriptions of program components that could be implemented by the City and regional partners to reduce salt contributions from point-of-use water softening systems were developed. HDR also reviewed existing relevant State regulations and City ordinances and policies to characterize the existing regulatory and authority framework. Refer to Section 5, Potential TDS Reduction Program Components, for additional information Considerations A salinity management program in the Phoenix area would need to be based on an assessment of current TDS sources and concentrations and the future water quality targets for specific water uses. From previous studies, a known source of TDS was identified as point-of-use water softeners. It was, therefore, necessary to further characterize the TDS contribution from point-of-use water softeners and subsequently identify policies and management methods that could be used to reduce the respective TDS contributions. Coupled with other salinity management program components that address other sources of TDS, the management of point-of-use water softeners could help achieve the overall salinity management program goals. To meet the City s salinity management goals, three main alternatives or a combination of these alternatives are available for each of the sewersheds: 1) The City can provide source water treatment to reduce hardness or salinity prior to delivery of potable water to customers. 2) The City can implement a salinity management program for users of the potable water system, including regulation of water softening devices. 3) The City can reduce TDS through the wastewater treatment process. This section focuses on the second alternative: to manage the salinity load that enters the City s WWTPs. Several program components could be implemented by the City to manage the TDS entering the WWTPs Public Education Actions to manage salinity impacts typically begin with a public education program. Significant SRWS salt discharge reductions can be achieved by improving the 11 Executive Summary

20 installation, operation, and maintenance of equipment being used by residential, commercial, and industrial customers. Communicating best management practices and the consequences to the environment of poor practices should be a common element of any comprehensive salinity management program. A public education program should engage users of the equipment for residential, industrial, or commercial softening as well as homebuilders and their installation contractors. The educational program should provide information on water softening alternatives that do not increase the TDS load in the sewershed and are comparable or lower in price than SRWS. This will require that a comprehensive evaluation be conducted to ensure that the alternative technologies adequately address the consumers hard water concerns and do not create other negative unintended consequences Standards Minimum performance standards should be established to ensure that systems used in the City are designed, operated, and maintained to be efficient with respect to water and salt usage. Performance standards have been developed for SRWS based on the current level of technology and economic considerations. Such standards have been applied to industry equipment certification programs and by certain jurisdictions that regulate the use of SRWS. Examples include the Water Quality Association s (WQA s) Gold Seal equipment certification program and the efficiency standards established in California. The WQA is a professional association representing the point-of-use water treatment industry. Implementing efficiency standards will help manage the salinity loading that comes from such devices into the future. A complementary measure would be to establish standards or a certification process for water softener installers. The WQA has indicated its support of such a certification to protect the quality of the industry. The proper installation of softening equipment is important to maintain high salt and water efficiencies Alternative Technologies Many products using alternative technologies may be capable of reducing hardness scaling for the residential sector of the softener market. However, there are no accepted U.S. standards for testing the hardness mitigating effects of products that employ technologies other than ion exchange or reverse osmosis. In addition, most of these products do not provide sufficient technical data to support advertised claims and are marketed based on testimonials rather than performance data. Of the many point-of-use processes described as having the potential to reduce hardness or the effects of hardness, the most reliable processes include reverse osmosis, ultrafiltration, distillation, capacitive deionization, and epitaxial crystallization. Further investigation and testing of alternative technologies could be a part of the City s overall salinity management program. Companies that market portable exchange water softening systems in Phoenix are working to reduce or eliminate brine discharges into the Phoenix sewershed. Portable 12 Executive Summary

21 exchange water softening systems involve the centralized resin regeneration of customer softening systems. The centralized processing of the ion exchange resin results in a brine waste stream that can be more easily controlled and managed Equipment Upgrades Similar to setting appropriate efficiency standards, upgrading water softening equipment to higher efficiency equipment can offer significant salt and water savings, reducing TDS produced from residential, commercial, and industrial water softeners. Salt efficiencies of SRWS keep improving. Newer models use less salt to soften more household water than older models. The effect of improved salt efficiency on TDS discharges is indicated in Figure 1.4. Softener Brine TDS with Varying Efficiencies (14 grain hardness) 30,000 Brine TDS from SRWS [mg/l] 25,000 20,000 15,000 10,000 5, Efficiency [grains removed/lb salt] Figure 1.4 Effect of softener efficiency on brine TDS In addition, the initiation basis for regeneration of the softener affects the TDS contribution. The chart in Figure 1.5 indicates that a time-clock-initiated regeneration cycle will regenerate more often, thereby increasing the amount of salts used over time compared with the DIR-controlled models with the same efficiency. 13 Executive Summary

22 Regeneration Frequency of DIR and Time Clock Controlled SRWS Regeneration [days] DIR Time Clock Hardness [gpg] Figure 1.5 Regeneration frequency of DIR and time clock controlled SRWS Equipment upgrades as a component of the salinity management program would complement a water softener efficiency and public education campaign. In addition, it could be coupled with a rebate program to encourage customers to upgrade to more efficient technologies such as demand-initiated or microprocessor regeneration. Locally, Culligan of Phoenix has initiated a program called Green Solutions 3 Step Plan to inspect its customers water softening equipment to ensure maximum efficiency. The City could encourage and/or require a more comprehensive program of equipment inspections and upgrades for residential, commercial, and industrial softening as part of its overall salinity management program Pretreatment Limits The City of Phoenix Pollution Control Division manages the pretreatment program designed to control industrial discharges into the sewer system to meet local limits on the City s WWTP Arizona Pollutant Discharge Elimination System (AZPDES) and Aquifer Protection Permit (APP) permits. Currently, TDS is monitored by the Pollution Control Division, but there is no established limit for industrial discharges. The TDS contribution to the sewer system from commercial and industrial facilities can be significant. In 2007, wastewater from industrial facilities in the pretreatment program had an average of 2,136 mg/l of TDS and 6.95 MGD. Efforts to reduce the salinity loads discharged from such sites can be effective and readily enforceable. The City s AZPDES pretreatment program provides a vehicle for addressing commercial and industrial discharges of TDS to the sewer system. The City should consider the role of commercial and industrial softeners in salinity management regardless of what steps it takes with respect to regulating residential SRWS systems. Currently, discharges from portable exchange regeneration facilities are not regulated. 14 Executive Summary

23 1.7.7 Rebates The City may decide to move beyond educational programs and set standards and/or discharge limits to reduce the TDS discharged to the sewer system. The development of a rebate program would be a next logical step. The City can offer a financial incentive to users of SRWS to upgrade to higher efficiency units, convert to an alternative technology (if feasible), or remove their water softener entirely. Several water or wastewater utilities have incorporated a rebate program as part of their overall TDS management strategy. The decision to offer a rebate program must consider the effectiveness of the preceding program elements along with the benefits and costs of the financial investment. A rebate program is certainly worth considering if it can bridge the gap toward meeting the reclaimed water quality target without needing to move to more costly and/or controversial options. Rebate program costs should be compared with treatment costs to meet the water quality goals, while considering impacts to water reuse customers Bans Actions to ban the use of water softening equipment should be viewed as a last resort. It is possible that a comprehensive salinity management program that incorporates many of the elements described above could achieve the City s goals without having to take this final step. It is also equally likely that one of the other options (TDS treatment of the source water or reclaimed water) could be more effective and/or appropriate for addressing the regional salinity problem than a ban on the use of SRWS. However, it is an option that must be considered if the City determines that it cannot achieve its reclaimed water TDS concentration targets through other alternatives. 1.8 Recommendations Program recommendations have been developed through the process of completing this study, as follows: The process of developing a salinity management program should be transparent and engage stakeholders early in the process. This has already begun through initial discussions with the WQA and homebuilders. Any initiative that would affect the water-softening industry in Phoenix would be a significant cause for concern to the local businesses that install softening systems. The WQA and some of its local constituents have stated a willingness to work with the City to develop a salinity management program. They have also demonstrated an aggressive track record of challenging regulatory programs that negatively affect their interests. The City needs to make a strong case for implementing regulatory actions that are deemed necessary. The regulatory or management driver that creates the need for the program must be clearly stated. Much of the scientific information about the accumulation and impacts of salts has been assembled through the Central Arizona Salinity Study. A benefit-cost analysis should be conducted and the results made available for review and comment. 15 Executive Summary

24 All sources of TDS that can be managed should be considered. As is necessary to achieve many water quality objectives, a multipoint or multibarrier approach is most cost effective. The regional salinity balance must be clearly understood before making conclusions or enacting regulatory measures. Regulatory actions that will yield the most benefit at the least cost and/or impact to local businesses and to the City should be prioritized. The salinity balance estimates developed in this study could be improved by: 1) verifying average source water TDS and hardness for each sewershed, 2) surveying the commercial sector for information regarding water softening activities, 3) developing and implementing a plan to conduct additional sampling and analysis of wastewater from residential and commercial sectors, and 4) refining the modeling assumptions used for the CCWRP sewershed. Multiple strategies, tailored specifically to each sewershed, should be considered as part of a comprehensive salinity management program, including: o Use TMDLs and NPDES permit limits to regulate TDS discharges o Establish a state/regional efficiency standard for all SRWS o Maintain a consistent monitoring and sampling program to demonstrate effects of program components o Educate homeowners on best management practices for their existing systems o Educate and/or certify operators of commercial/industrial units o Require certifications for system installers o Research new technologies and practices (e.g., off-site regeneration and alternative technologies) o Require use of approved equipment Action is needed to reduce and/or eliminate water softening activities within the service area; therefore, the following items should be implemented: o Work with industrial, commercial, and residential users of SRWS to maximize efficiencies o Take actions to prevent new systems from being installed during new construction o Require system removal upon remodel or resale o Provide incentives/rebates for homeowners to remove existing systems o Ban the use of water softeners, as a last resort Measure the results of the program on a continuous basis. Potentially phase in more aggressive measures over time as necessary to meet the management objectives. Evaluate alternatives to regulating water softening activities in the service area. One primary alternative would be to perform point-of-use treatment for reclaimed water distribution and/or discharge. 16 Executive Summary

25 1.9 References TNT Technology Company. February 24, CASS / Cave Creek Water Reclamation Salinity Study. Kiester, Timothy. Non Chemical Devices: Thirty Years of Myth Busting. Presented at 2004 International Water Conference. Retrieved from: Central Arizona Salinity Study (CASS). December Phase I. Salinity Control at Wastewater Treatment Plants. Retrieved from: Bruursema, Tom. Water Softeners and Septic Tanks: Are They a Compatible Combination?. NOWRA 2005 Conference presentation. McKenzie, Executive Summary

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27 2 TDS Contribution Estimates 2.1 Description Phoenix wastewater accumulates, on average, 400 mg/l of TDS in the flow pathway between source waters and the WWTPs. It has been estimated that 26 percent of this increase in TDS is attributable to water softener discharges. The City requested HDR to verify this estimate, or to recalculate it based on additional and new sources of information. HDR reviewed numerous salinity studies completed in Phoenix and elsewhere to develop a modeling approach for estimating the percentage of TDS, by sewershed, that is attributable to point-of-use water treatment devices. The information presented in this section builds on previous research to determine the TDS impact from softening activities without performing additional wastewater monitoring or sampling. Additional surveying of Phoenix homebuilders, softener vendors, and the industrial sector was performed to develop new data for this study. 2.2 Previous Studies The CASS indicated that 73 percent of TDS received annually at the 23rd Avenue and 91st Avenue WWTP originates from source water, 11 percent comes from industry, and 16 percent is from residential and commercial sources (CASS, 2006). Some of the information developed in the CASS reports comes from salinity studies performed to determine the TDS impact specific to the CCWRP sewershed resulting from residential water softening. These studies include an American Water Works Association Research Foundation (AwwaRF) case study completed in 2004 and the Cave Creek Water Reclamation Plant Salinity Study completed in Another study reviewed included a 2002 Sanitation District of Los Angeles County (LACSD) report on the sources of chloride in Santa Clarita. This comprehensive study identified chloride in water and wastewater systems and quantified the effect of SRWS. These three studies were reviewed for information pertinent to the estimation of TDS due to water softeners and strategies for additional investigation. The following sections describe approaches and results from each of the studies. Previous studies vary in their approach to estimating the water softener use and correlating factors such as age of home, income, location, etc.; and in their approach for determining TDS concentrations from SRWS. The results from these studies are not easily transferable to other communities because of differences in water chemistry, water demand, end uses, and behavioral characteristics. However, specific information from these previous studies was used develop modeling assumptions to estimate TDS resulting from the use of water softeners in the Phoenix sewersheds. 19 Section 2 TDS Contribution Estimates

28 AwwaRF Study In 2006, AwwaRF produced a report entitled Characterizing and Managing Salinity Loadings in Reclaimed Water Systems. The report included background material on salinity and water softening and recounted six case studies from California, Arizona, and Texas water utilities. Surveys were performed in each area to determine the number of residences using SRWS. In addition, wastewater monitoring and sampling were performed on residential sewers to identify the range of TDS concentrations. Table 2.1 summarizes the results from the six case studies indicating impacts of water softening. Table 2.1 Summary of TDS increase from AwwaRF case studies (AwwaRF, 2006) Location Source TDS Residential 1 Max TDS sampled TDS spike attributed to Residences with Softeners 3 [mg/l] [mg/l] [mg/l] % Santa Clara, CA water softeners and industrial 31.3 Phoenix, AZ water softeners 29.2 Monterey, CA (2) 864 water softeners 21.3 Irvine Ranch, CA water softeners 12.1 Inland Empire, CA water softeners 10.3 El Paso, TX water softeners TDS increase over source TDS from sewer basins with 90% or more flow from residential sector. 2. Residential TDS range does not include Moss Landing sewer basin which is impacted by seawater intrusion. 3. Have and use water softener based on AwwaRF, 2006 survey of selected sewersheds. The AwwaRF case studies indicate TDS concentration increases from softening between 200 and 500 mg/l over source water concentrations. However, correlating the percentage of residences with softeners and TDS increases, as indicated in Figure 1.6, does not completely describe the rate of TDS increase (R 2 = 58%). If Phoenix water softener use was closer to the Reclamation survey results for CCWRP (about 50 percent), the relationship is much stronger (R 2 = 90%). TDS concentrations are shown to increase with softener use, but the rate of increase is not predictable from data available. The rate of TDS increase also depends on the volume of wastewater from sources other than SRWS brine and softener efficiencies and operation, which affect the blending proportions of daily salts to the total wastewater volume. 20 Section 2 TDS Contribution Estimates

29 Relationship of Softener Use to TDS increase % households using water softeners R 2 = TDS increase over background [mg/l] Table 2.2 Relationship of softener use to TDS increase based on AwwaRF studies (AwwaRF, 2006) AwwaRF Study Phoenix Case Study The 2006 AwwaRF report included a case study on the TDS influent to the CCWRP in Phoenix. During the study period, the CCWRP received an average of 2.35 MGD; 90 percent originated from residential sources and 10 percent from commercial. Source water for the service area averages 511 mg/l of TDS. The study included two sampling events between June 2003 and February The first analysis identified the TDS fluctuation in the main trunk lines from the Cave Creek and the Mayo sewersheds to the CCWRP. The TDS spiked at 3,220 mg/l in the mainly residential Cave Creek sewershed; this spike occurred between 3 and 5 a.m., and was assumed to result from water softener use. The second analysis measured water demand at seven isolated residences and TDS outflow over a 5-day period to correlate residential activities to increase in TDS in the sewer. Residential water activities were assumed based on the water demand, time of day, and duration of demand. The average total salt loading from the residences was 1.04 lb/residence/day. Total wastewater generation was calculated at 209 GPCD, based on 2.5 per household. Results of the study indicated that 15.7 percent of household salts came from SRWS. Sampling results are shown in Table Section 2 TDS Contribution Estimates

30 Table 2.3 Sampling results for CCWRP case study (AwwaRF, 2006) Table 15.7 Residential and commercial TDS contributions City of Phoenix Residential 1 Commercial 1 Total model TDS (mg/l) Water source TDS (mg/l) Model TDS increase (mg/l) % TDS Contribution Total model TDS (mg/l) Water source TDS (mg/l) Model TDS increase (mg/l) % TDS Contribution Cave Creek % % Interceptor Mayo Interceptor % % Total 84% 16% 1 Modeled flows and TDS are estimated based on the best available information. Although, the study did attempt to isolate the TDS increase in the waste stream from SRWS; the results have limited benefit due to the sampling approach and modeling assumptions. The study identified demand for interior water uses; however, the indoor water demand was not calibrated or verified. The study assumed that all water demand was for interior uses resulting in a high wastewater return flow (209 GPCD), which is nearly three times higher than the City of Phoenix estimates for newer single family residences (Frost, 11/17/08 correspondence). TDS concentrations were estimated through electroconductivity measurements and grab samples were not collected and analyzed for TDS to confirm the results. Although the study quantified TDS contributions from commercial, it did not further investigate impacts from commercial water softening in the sewershed TNT Technologies CCWRP Salinity Study Feb, 2006 Another study on the CCWRP sewershed was the TNT Technologies CCWRP Salinity Study completed in February This study compiled field results from interviews with commercial businesses using SRWS in the sewershed and a week long sampling program on specific sewer lines receiving flows from residential or from commercial. This study differed from the sampling approach compared to the previous AwwaRF study and based conclusions not on conductivity measurements but from laboratory analysis of specific TDS analytes. Sodium, chloride and potassium were analyzed, assuming all increases in these constituents were from water softening activity. Residential sampling was conducted at locations that represented varying age of neighborhoods and with majority of flows from residences. Table 2.4 identifies the sampling locations and the estimated softener use based on analytical results. Wastewater flows at the CCWRP were predicted at 86 GPCD; however, current flows were determined to be less than 64 GPCD. The impact of lower flow rates can lead to higher TDS concentrations since there is less dilution of the salts. 22 Section 2 TDS Contribution Estimates

31 Table 2.4 Residential locations sampled and estimated softener use based on analytical results Name Accounts Age Est. Softener Use Desert Ridge % Dove Valley % Tatum Ranch % The oldest neighborhood sampled had the lowest TDS while the newest had the highest. The study concluded higher TDS concentrations in newer neighborhoods were from higher percentage of SRWS use and lower wastewater flows. The study also included TDS contributions from the J.W. Marriott Resort, Mayo Hospital, American Express, Desert Ridge Marketplace, and Pinnacle High School. The study concluded that: Chlorination contributes 3 percent of TDS at the CCWRP Water supply contributes to 49 percent of TDS Residential activity and softeners contribute 36 percent of TDS Commercial softening contributes 12 percent of TDS The TNT study included a well developed sampling approach. However, results are skewed since all increases in analyte concentrations were assumed to be from water softeners. Other studies (AwwaRF, 2006; SCVJSS, 2002) indicate that more than 20 percent of residential TDS increases may be from other water uses including toilets, clothes washing machines, dishwashers and pools Santa Clarita Valley Joint Sewage Salinity Source Report 2002 Due to high levels of chloride discharging into the Santa Clara River, the LACSD undertook a large regulatory and investigative campaign to reduce chloride inputs that flow into Saugus and Valencia WRP. The study was reviewed by the National Water Research Institute (NWRI) to meet California state law for utilities seeking to control residential SRWS. The investigative study identified major sources of chloride including local water supply and residential wastewater. The study concluded: The potable water supply contributed 42 percent of the chloride Residential SRWS contributed 33 percent of the total chloride concentration. 11 percent of the residences were using SRWS Other residential wastewater contributed 13 percent of chloride Commercial and industrial contributed 7 percent of chloride. Liquid disposal assumed to contribute remaining 5 percent The information on the SRWS was developed through door to door surveys and extensive sampling and analysis. Six neighborhoods were selected for survey and sampling based on the age of the neighborhoods and sufficient flows for 24 hr sampling in a single 23 Section 2 TDS Contribution Estimates

32 common sewer for the neighborhood. The survey indicated a lower percentage of SRWS in homes built prior to 1997 which may be due to the 1968 prohibition of SRWS in effect until Sampling was conducted using standard methods for 24 hr composite sampling grabbed every 15 minutes for one week. In addition to sampling, flow monitoring was completed during the sampling period to determine the chloride mass loading. The chloride concentrations for the older neighborhoods without SRWS was 6-12 times less than the chloride loading compared to the newer neighborhoods (post 1997). The nighttime chloride signature also spiked in the newer neighborhoods, which is reflective of the tendency of SRWS set to recharge during nighttime periods. The study analyzed additional information regarding the property size, value and taxes to determine a regression equation for estimating chloride concentrations for single family homes. Non SRWS chloride concentrations of 30 percent from residences were determined from literature review and product information for common household cleaning products, soaps, pool backwash, etc. In addition to residential sampling, an experiment was initiated in 2001 to analyze the operation of an efficient SRWS and the impact to chloride concentrations (see Table 2.4). The experiment used a General Electric Smart Water Softening system Model No. GXSF39B with an efficiency of 5,168 grains / lb. The demand on the system was controlled to mimic an average household with a diurnal demand pattern. The model is a demand initiated regeneration (DIR) unit and utilizes 7.45 lb of NaCl during regeneration and removes nearly 30,800 grains of hardness per regeneration due to the capacity of the resins. Samples were collected prior to passing through the softener, in the softened line and brine discharge line. Average volume of brine discharged was 47 gallons. Chloride concentrations averaged 10,300 mg/l. Sodium concentrations averaged 4,631 mg/l. Results in the softened line indicate that 97 percent of the hardness was removed and 9 mg/l of Na and 2 mg/l of Chloride are added for every grain of hardness removed. Table 2.5 Sampling from SRWS (SCVJSS, 2002) Concentration [mg/l] Constituent presoftenesoftened post- brine Calcium Chloride ,284 Magnesium 14.4 < Potassium Sodium ,631 Sulfate total hardness * 125 <5 4,123 * mg/l CaCO 3 Values based on average over 5 months of sampling The average chloride concentration of the brine is closely related to the chloride concentrations analyzed during the sampling of the newer neighborhoods during the nighttime period chloride spikes. 24 Section 2 TDS Contribution Estimates

33 Over 3,000 industrial dischargers are regulated through source control programs. Sampling was conducted to determine the chloride loading from each permitted facility. Flow data was developed through water usage records or flow monitoring data. There is only a small potential for additional chloride reduction from industrial sources. Analysis determined that the flow weighted average of 128 mg/l of chloride from the 1.5 MGD industrial discharges slightly reduces chloride concentrations entering the WRP from blending. Site inspections were conducted of commercial users of water and potential water softeners which included beauty salons, car washes, dry cleaners, health clubs, hotels, laundromats, and non fast food restaurants. Commercial and industrial brine discharge from SRWS to sewers has been prohibited since Most commercial entities utilize portable exchange softening units. Following an inspection, sampling of the wastewater was conducted to develop a representative chloride loading from each commercial entity. Chloride mass discharge rates were developed for all commercial entities using wastewater flow rate and associated chloride concentrations. As a result, it was determined that commercial only contributes 4 percent of the total chloride loading at the WRPs with a flow weighted average of 113mg/L. This is lower than the average effluent chloride concentration at the WRP of 168 mg/l. In summary, the LACSD study demonstrates a thorough approach for identifying problem salt sources in wastewater through the use of well designed surveys, sampling and analysis program, site inspections and long term monitoring of SRWS. The robust study was required for the LACSD to decide to regulate residential SRWS after identifying all sources of chloride and evaluating alternative steps for reducing chloride from commercial and industrial sources. The study includes the monitoring of a SRWS operation which provides additional information for modeling assumptions of SRWS for other utilities. The LACSD Santa Clarita study is one of the most robust studies combining excellent empirical data, with modeling and with surveying as a sample to be applied to other communities. However, since the LACSD study focused on chloride, there is limited application of results to the Phoenix sewersheds for TDS. The empirical data from the SRWS monitoring and sampling can be used to model salts added from individual SRWS. The results from Santa Clarita Valley can not be transferred to Phoenix since there are many differences in water chemistry, water demand and end uses and behavioral characteristics Estimating Residential Sources of Salts The AwwaRF and the TNT Technologies studies on the CCWRP provide particular information on the TDS increase from residential uses with varying approaches and conclusions. However, neither study analyzed the sources of salts from all residential water uses. The LACSD study focused on sources of chlorides and not TDS in general. 25 Section 2 TDS Contribution Estimates

34 Human wastes, grey water, and swimming pools can add a certain percentage of salts to the sewer. Identifying the TDS increase for all household uses would isolate the impact from each use including water softening. It is therefore important to determine how much salt is added to the wastewater from residential uses other than water softening. There has not been any recent field research in the US which attempt to determine this information. The most comprehensive US based research was conducted in 1976 by Siegrist and 1978 by Brandes. Changes in household water uses, efficiencies of dishwashers and washing machines and composition of detergents affect the current applicability of these studies, but they provide some insight into sources of salts. Using previous research, dietary and behavioral information, the 2006 AwwaRF study calculated human physiological losses as salts to raw wastewater at a rate of 72,881 mg/person day (Figure 2.2). Figure 2.1 Data tables from AwwaRF, 2006 To determine the TDS concentrations associated with various interior water uses, HDR based the modeling assumptions on a 1999 study by Mayer, et al., which disaggregated residential wastewater flows into specific uses of indoor water use in Phoenix. Mayer determined the average gallons per capita per day (GPCD) for indoor uses in Phoenix was 77.6 gallons. An estimate of indoor uses is in Table Section 2 TDS Contribution Estimates

35 Table 2.6 Indoor water use for average Phoenix residence (Mayer, 1999) Phoenix GPCD % toilet % clothes washer % shower % faucet % leaks % bath % dishwasher % other % TOTAL % Using the existing information from the AwwaRF and Mayer studies, HDR developed the potential percentage of TDS by source from residential water use (Table 2.7). For the residential TDS analysis, a residence was assumed to have 2.5 occupants, a self regenerating water softener, a pool and a general usage of water similar to the Mayer study for Phoenix. Based on these assumptions and 650 mg/l TDS source water, the total wastewater flow from the residence is 203 gallons per day with a TDS of 1,387 mg/l. The household discharges a total of 2.35 lbs/day of salts. Table 2.7 indicates the estimated sources of TDS for residential water uses. Table 2.7 Salt sources and flows from average Phoenix residence Salt Source Avg daily Household Avg Daily Avg Daily Source salts (3) Discharge daily salts TDS Salts Water Total salt [grams/person] [grams/day] [GPD] [mg/l] [lb/day] [lb/day] [lb/day] human wastes (3,1) grey water (2,1) swimming pools (4) SRWS (5) , Total Discharge per day is based on percentages from developed by Mayer, 1999 for Phx multiplied by GPCD for the sewershed 2 - Includes washers, faucets, shower, bath, leaks 3 - Values from AWWARF Assumes 14 day backwash cycle at 120 gallons for a medium sized pool in Phoenix with 3yr old water (3392 mg/l TDS). Source: AWWARF, Henry Day 5 - Assumes demand initiated regeneration softener with 3000 g/lb salt efficiency, 30,000 grain capacity, 50 gallons per regeneration cycle (Type 3 softener) and 12 gpg hardness in source water. Regeneration calculations included in Appendix A. AvgHousehold Salt lb day mg grams 1000mg TDS = L day capita day gram L lb gallons = TDS( mg / L) 8.34 mg MG day capita household use gallon MG 1,000,000gallons gallon L Studies indicate that human physiological losses of salts to raw wastewater represent 72,881 mg/day (Figure 2.2). Assuming 2.5 people per household and the derived 19.6 GPCD for toilet use, human wastes make up 17.1 percent of the total salt discharge from the residence. Grey water includes water that is discharged from sinks, clothes washers, dish washers, showers, and bathtubs which may include detergents, food wastes, and household 27 Section 2 TDS Contribution Estimates

36 chemicals. Siegrist and Brandes studies indicate a mg/l range for grey water TDS; however, the daily contribution from detergents may only be 10 grams/capita and from food wastes at 2 grams/capita (AwwaRF, 2006). Using the 12 mg/l salt contribution for the calculation, 2.8 percent of the total salt discharge is attributable to grey water (detergent and food wastes). Swimming pools did not introduce a significant amount of salts into the waste stream to impact total daily TDS from the household. However, backwashing generally occurs every two weeks which would show a larger spike in TDS on the backwash day. Similarly, TDS from demand initiated SRWS occurring every 2,000 gallons or once every 10 days would create a spike on the regeneration day. Calculations in Table 2.7 assume a SRWS was 3,000 grains hardness removed per pound of regenerant salt used. If an average of 12 grains of hardness is assumed for source water, and 50 gallons of water is used for regeneration, the TDS from the softener discharge per day is 18,453 mg/l. The calculation for the regeneration, TDS and amount of salts used per cycle is included in Appendix A. Variations in source water hardness and the type of regeneration control will affect the regeneration cycle (Figure 2.3). Increase in regeneration in the time clock controlled SRWS will increase the amount of salts used over time compared to the DIR controlled models. In addition, the salt efficiency of the softener (Figure 2.4) impacts the resulting TDS of the SRWS brine during regeneration. Regeneration Frequency of DIR and Time Clock Controlled SRWS Regeneration [days] DIR Time Clock Hardness [gpg] Figure 2.2 Regeneration frequency of DIR and time clock controlled SRWS 28 Section 2 TDS Contribution Estimates

37 Softener Brine TDS with Varying Efficiencies (14 grain hardness) 30,000 Brine TDS from SRWS [mg/l] 25,000 20,000 15,000 10,000 5, Efficiency [grains removed/lb salt] Figure 2.3 Average daily softener TDS based on salt efficiency of softener and 14 grains hardness source water In summary, approximately 47 percent of the total salts from households in Phoenix may be from source water. Other residential salt sources besides water softeners include human physiological losses, detergents, food wastes and pools which may attribute up to 20 percent of total salts from the households. The remaining 33 percent of salts could be attributable to SRWS (Figure 2.5). SRWS 33% Source Water 47% Detergent & Food Waste 3% Human Wastes 17% Figure 2.4 Salts, by source, from residential based on Table Residential Use of Water Softeners in Phoenix Previous studies have focused on randomly selected homeowners in the Phoenix metropolitan area to participate in a survey about their water softener use. From this data, water softener use projections have been developed for probable penetration increase and resulting TDS impact. Results indicate that between 24 percent (Reclamation, 2004) and 29 percent (AwwaRF, 2006) of households have and use water softeners for their interior 29 Section 2 TDS Contribution Estimates

38 water use. Research indicates that there is an increasing trend for water softening in newer neighborhoods and for wealthier households. Water softener, reverse osmosis and pool ownership increases with disposable income (Reclamation, 2004). Studies have attempted to associate various factors to determine the probability of an individual owning a water softener. Statistically significant factors resulting from these studies include age of home, home ownership, household income, property valuation, and perception of water quality. An AwwaRF survey completed in 2003 of six municipal areas in California, Texas and Arizona developed a regression equation (R 2 = ) predicting water softener use as a function of household income (AwwaRF, 2006). Surveys indicate that households soften varying amounts of water including all water use (37 percent), all interior water (45 percent) or only hot water (9 percent). Additional factors affecting the efficiency of the water softeners is if the system is maintained by the owner or someone else, timer controlled versus demand initiated, efficiency of softener, portable exchange units and type of salts (NaCl or KCl) used for regenerating the resins. The difficulty in predicting water softener penetration for a municipality is the complex and interrelated issues of income, value, water quality perception, size of home, etc. The 2002 Santa Clarita Valley study identified six neighborhoods to complete door to door surveys which were representative of varying construction years, home values and house sizes. Correlating the various factors with the results from a sampling program for chlorides from each neighborhood resulted in a regression equation for predicting chloride concentration from the neighborhoods: Y = *[Assessed Property Value] *[2001 Property Taxes] *[Sqft building] The Reclamation survey conducted in Phoenix in 2004, developed softener penetration percentages that were based on the construction year of the home. Newer homes had more than 50 percent probability of operating a water softener, compared to a 17 percent penetration for homes constructed prior to Many homebuilders include options for water softeners as part of the house and generally plumb a loop system for an after market installation. The TNT study developed higher penetration estimates based on sampling data but validated the significant difference for softener use with age of home. Table 2.8 indicates the softener penetration for the Phoenix area based on construction year for the two studies. Table 2.8 Softener penetration in Phoenix based on home construction year Softener Penetration Construction Year (Reclamation, 2004) (TNT, 2006) < % 1970s 23% 1980s 1990s 27% % 47% % % 68% 30 Section 2 TDS Contribution Estimates

39 The Reclamation survey results and the TNT estimates indicate an increasing trend for softeners in newer homes. To characterize the penetration of water softeners into the City of Phoenix, homebuilders and water softener vendors were surveyed as part of this study Homebuilder survey Homebuilders were selected based on market share and ongoing development projects in Phoenix to participate in a survey on water softeners included in Phoenix homes. Initially 10 homebuilders were selected representing single family, townhouses, condominiums, and multi family units but because of the current downturn in the housing market only 6 of the ten were available to respond to the survey. The survey was used to identify the percentage of homes constructed or sold in 2007 which included water softening systems or plumbed with loops for after market softener installation. Survey results are in Table 2.9. A copy of the survey is included in Appendix B. Table 2.9 Homebuilder survey summary Avg Home Units built/sold in % of units with Included loop Company Price 2007 softeners plumbing Pulte Homes $250 K % 30% Taylor Morrison $240 K % 55% Toll Brothers $900 K % 100% Communities Southwest N/A N/A N/A N/A Gray Development 500 0% DR Horton (Continental, Dietz-Crane) NR NR NR NR Richmond American $237 K 1210 A NR NR Totals % 35.9% N/A - Not Applicable NR - No response A - units sold not included in total since other data was not provided Respondents indicated that 5,374 homes or apartments were constructed in 2007 in Phoenix. Of those nearly 17.4 percent included a water softener. All of the homebuilders offer to include water softeners and / or reverse osmosis treatment systems in new homes. Homebuilders indicated that water treatment systems are represented as a selection for the homebuyer and are not installed unless a buyer requests it. There may be some marketing of the softeners by the homebuilders including presenting material on water softening and water quality. 31 Section 2 TDS Contribution Estimates

40 Respondents indicated that loop systems for after market water softener installations are installed in 35.9 percent of the homes even if the buyer does not request it. Systems are usually plumbed to soften all interior water. Only one homebuilder indicated that only the hot water line was softened. Installation of softeners is performed by either the vendor or a contracted plumber. Reclamation and TNT estimates that 51 to 68 percent of newer homes use water softeners. Based on the homebuilder survey data, homebuilders may only account for less than half of the SRWS installations in new homes while the majority are being installed after market Water softener provider survey A number of water softener providers were surveyed to gather information on the quantity, types and characteristics of softeners being sold in the Phoenix market. There are numerous companies selling water softeners in the Phoenix area. The vendors who were selected to be surveyed were in good standing with the Water Quality Association (WQA) and represented various water softener brands. Responses to the survey are contained in Appendix C. A total of 5,982 softeners were sold by the surveyed vendors within the Phoenix market. Excluding the portable exchange softeners, 100 percent of softeners sold by the surveyed vendors were demand initiated regeneration softeners 1. Systems range in cost from $400 to $4000 with varying model sizes. Models range in capacity, salt efficiency, and water efficiency. The average salt efficiency for all of the models sold by the surveyed vendors in 2007 was 4,496 grains removed/ lb of regenerant salt. Average water usage per regeneration was 52 gallons. Appendix C summarizes the survey responses. For a 30,000 grain capacity SRWS-DIR regenerating once a week and a source water hardness of 14 gpg, a salt efficiency of 4,496 grains removed/ lb of regenerant salt calculates into 0.77 lb/day of salt. The survey is not comprehensive of all the models sold in Phoenix but it does indicate that salt and water efficiencies continue to improve on newer models. Information from the WQA indicates that nearly 22 percent of SRWS units shipped in the US during the first 8 months of 2008 were fitted with time clock valve controls (Jensen, correspondence). 1 One distributor responded that 9% of softeners sold in 2007 were time clock devices. However, this was not included in the calculations since it was unknown if the softeners went to homeowners or vendors out of state. 32 Section 2 TDS Contribution Estimates

41 Table 2.10 Water softener vendor survey results 2007 Sales SRWS regeneration Salt efficiency Brine Vol Company Brand Cost [$] Total After market Builders time clock DIR [grains/lb salt] [Gal/cycle] AZ Watertech Industries % pureonics 1,300-3,500 none 100% JB Sales 30 80% 20% GE NR none 100% Pristine 1 40% 60% GE 2 NR (a) 100% 4500 (b) Canyon Quality Water % 0 Nelson, B&R none 100% 2667 c 65 c Advantage Pure Flow % 0 Water Resources International % 0 Advantage Pureflow system none NR United Standard Hydro-Quad none 100% Kinetico 4 NR 97% 3% Kinetico NR none 100% Boyetts Rayne of Mesa % 27% RXD NR none 100% Culligan % 35% Culligan NR none 100% Rayne % Rayne none 100% B&R % 22.5% proprietary 9% 91% Totals , NR - No response 1. Pristine services and installs and is a major contractor for GE. Specific data could not be shared about sales to home depot because of a confidentiality clause. Majority of installs are for new homes. 2. GE sold to Pentair which uses the name Fleck. Home Depot has their own model which is high flow, high capacity and predictive 3. 20% customers using KCl. Manage and service the systems yearly. 4. Kinetico does not use any electricity and regenerates based on volume of water through the system. So it can regenerate at any time. 5. Includes SRWS and portable exchange tanks 6. Manufacturer and distributer of SRWS. Number sold is not included in the total since B&R sales include those sold to other vendors and out of state. a. Unless a customer asks for the time clock controlled SRWS, they don t sell them. Used mostly for advertising low cost SRWS. b. Not a fixed brine volume c. No response from vendor, efficiency and brine volume estimated from other responses 33 Section 2 TDS Contribution Estimates

42 2.3.3 Modeling Assumptions for Residential Water Softening Using information from the Maricopa County Assessors database and the City of Phoenix, residential units were categorized by age of home according to the Reclamation groupings (Table 2.11). Table 2.11 Total number of single-family residences, by age and sewershed CCWRP 23rd 91st Total < ,908 55, , ,390 72,932 85, ,934 61,919 70, ,528 4,219 49,861 62, ,144 6,246 54,803 73,193 Total 20,809 91, , ,024 The Reclamation survey conducted in Phoenix in 2004, developed softener penetration percentages that were based on the construction year of the home. Newer homes had more than 50 percent probability of operating a water softener, compared to a 17 percent penetration for homes constructed prior to Table 2.12 indicates the number of households with water softeners in each sewershed based on the Reclamation water softener penetration study. Using these percentages, 125,079 households are using water softeners representing nearly 31 percent of the single family residences in the City. Table 2.12 Residences with softeners based on Reclamation survey (2004) Age of Residence Softener Penetration 1 CCWRP 23rd 91st < % 0 10,184 9, % 3 2,850 16, % 33 2,412 16, % 4,008 1,983 23, % 6,193 3,185 27,950 Total 10,237 20,614 94,228 % with softeners / sewershed 49.2% 22.5% 32.0% 1 - Based on USBR Study (2004) Water softener efficiencies have improved significantly since their introduction into the market. Although the timeline of efficiency improvement is not well documented, models can range from 2,000 grains/lb to over 4,500 grains/lb with varying brine volumes. The vendor survey indicated that the average efficiencies of models for 2007 sales were 4,500 grains/lb and used approximately 52 gallons for regeneration. There is no reliable data for determining the salt efficiencies of the SRWS installed in residences in the Phoenix sewersheds. However for modeling purposes, four scenarios were developed by HDR to analyze the potential salt efficiencies of SRWS in the Phoenix sewersheds. Table 2.13 indicates the various scenarios modeled. Older or cheaper models will have low efficiencies of 2,000 grains/lb and may be demand initiated regenerated (DIR) or controlled by a time clock and were modeled representing 20 to 34 Section 2 TDS Contribution Estimates

43 30 percent of the total SRWS. Mid quality models (3,000 grains/lb) installed in the late 1990 s represent 30 to 65 percent of the total SRWS. Newer high efficiency models with 4,000 grains/lb represent 10 to 40 percent of the total SRWS in the four scenarios (A-1, A-2, A-3, and A-4). The calculation for the regeneration, TDS, and amount of salts used per cycle for each efficiency modeled is included in Appendix A. Table 2.13 Modeling scenarios for SRWS efficiencies Control Volume Efficiency Capacity Reserve % Penetration of Softener Type [Gal] [grains/lb] grains A-1 A-2 A-3 A-4 Time Clock 60 2,000 30,000 23% 10% 5% 10% 0% DIR 60 2,000 30,000 23% 15% 15% 20% 20% DIR 50 3,000 30,000 23% 65% 60% 30% 40% DIR 45 4,000 30,000 23% 10% 20% 40% 40% 2.4 Industrial and Commercial Softening Industrial water softening survey The City of Phoenix has developed an industrial pretreatment program to monitor and regulate wastewater flows from industry to protect the WWTP, worker safety and effluent water quality. Currently, there are 92 industrial dischargers that are permitted through the pretreatment program. The average flow from these industries represents 6.95 MGD with TDS of 2,136 mg/l representing 123,882 lbs/day of salts. Assuming a 650 mg/l for source water, 37,700 lb/salt or 30 percent is due to source water salts. The pretreatment program monitors TDS but has not established a local limit for the industries. HDR performed a survey of these industries to determine the amount of salt from water softening. A total of 63 industries completed a survey indicating 77 percent of these industries soften their water. Responses indicate that there is some attempt to recapture some of the brine and treat it prior to discharging it to the sewer. However, 67 percent of respondents discharge regeneration brine to the sewer. Survey results indicate that industries soften between 5 percent and 100 percent of all interior water with regeneration cycles ranging from daily to once a week. Respondents indicated that between 60 and 40,000 lbs of salt is used each month for industrial water softening. Copies of the survey and responses are included in Appendix D. Based on the completed surveys, 8,772 lbs of salt is added each day by industrial water softening. This represents 17 percent of the total salts added above source water in those industries that responded. Assuming that this percentage is consistent with those industries that did not respond to the survey, the total salt load from industrial water softening is approximately 14,651 lb/day. The remaining 58 percent of salts from the industrial pretreatment program are assumed due to industrial activities. 35 Section 2 TDS Contribution Estimates

44 2.4.2 Commercial Softening The 2006 TNT Study for the CCWRP quantified annual salt usage from six large commercial contributors including JW Marriot Resort, Desert Ridge Marketplace, American Express, Scottsdale/101, Mayo Hospital and Triangle Bell. The combined annual salt usage for water softening from these facilities was 826,064 lbs. Flow data from these facilities was not included in the 2006 TNT report. SRWS are commonly used in the commercial sector for car washes, non fast food restaurants, laundromats, hotels and hospitals. To determine the potential salt added from commercial softening, the City provided HDR water demand data for car washes, restaurants, laundromats and hotels for each sewershed (Appendix A). It is likely that each of the mentioned businesses used softened water except for possibly fast food restaurants. To model the impact of the commercial softening, it was assumed that each commercial entity used softened water for all interior uses except for 50 percent of the restaurants. Interior uses were estimated at 87 percent of the total water demand. Commercial impacts are defined for each sewershed in Section 2.5. Similar to the scenarios developed for the modeling of residential softener efficiencies, Table 2.14 describes the four scenarios (B-1, B-2, B-3, B-4) used for modeling commercial SRWS. Table 2.14 Commercial scenarios for SRWS efficiencies in the sewersheds Control Volume Efficiency Capacity Reserve % Penetration of Softener Type [Gal] [grains/lb] grains B-1 B-2 B-3 B-4 Time Clock 60 2,000 30,000 23% DIR 60 2,200 30,000 23% 100% 50% DIR 50 3,000 30,000 23% 100% DIR 50 3,300 30,000 23% 100% 50% In addition to these sources, Rayne and Culligan operate centralized regeneration facilities for portable exchange tanks in the Phoenix sewersheds. In 2007, these facilities used approximately 1.1 million pounds of salt for regeneration which is discharged directly to the sewer. Both of the facilities are working on designs to reclaim 25 to 100 percent of the brine prior to being discharged to the sewers (Oberhamer, correspondence). To model this salt source, 3,039 lb/day of salt is introduced into the 23rd Avenue WWTP sewershed. 2.5 Estimate of TDS from Water Softeners by Sewershed Phoenix has three WWTPs including the 8 MGD CCWRP, the 60 MGD 23rd Avenue WWTP, and the 179 MGD 91st Avenue WWTP. In 2007, the average influent TDS for 23rd and 91st was 1,030 mg/l and 1,055 mg/l respectively, corresponding to 1.61 million pounds of salt that is passing through the plants each day. 36 Section 2 TDS Contribution Estimates

45 Table sewershed TDS and flow Sewershed Flow TDS Salts % of Total [MGD] [mg/l] [lb/day] CCWRP 4.4 1,121 41, % 23rd Ave WWTP , , % 91st Ave WWTP 132 1,055 1,161, % Total ,050 1,614, % Nearly 42 percent of these salts are attributable to the Phoenix source water (Figure 2.6). Other salts are added by residential, commercial and industrial use of the water and flows from other cities into 23rd Avenue and 91st Avenue WWTP. Previous studies (Table 2.7) indicate that 0.47 lb/day of salts per household may be from human wastes, detergent and food wastes. There are a total of 407,024 single family residences in the Phoenix service area. The salt loading just from human wastes, detergent and food wastes single family residences constitutes 12 percent of the total salts received at the plants. The remaining 46 percent of salts are from the other cities, water softening activities and other uses commercial and industrial. Other (+ softening) 46% Source 42% Residential (nonsoftening) 12% Figure 2.5 Salt sources To determine the amount of TDS due to water softening activities, results were compiled from the previous studies, as well as the vendor, homebuilder and industrial surveys. The Phoenix service area was grouped by specific sewersheds including 23rd Avenue WWTP, 91st Avenue WWTP and CCWRP rd Avenue WWTP In 2007, 23rd Avenue WWTP received on average 11.1 MGD from other cities including Tempe and Mesa with a TDS of about 1,000 mg/l or 92,499 lb/day of salts (Lopez, correspondence). There are approximately 91,697 single family dwelling units that discharge into the 23rd Avenue WWTP sewershed. Using the penetration data from the Reclamation survey and SRWS efficiency scenarios indicated in Table 2.13, between 37 Section 2 TDS Contribution Estimates

46 16,080 and 17,919 lb/day of salt is added to the 23rd Avenue WWTP sewershed from residential water softening. For modeling purposes, it was assumed that the 23rd Avenue WWTP sewershed received 40 percent of the industrial discharges from the pretreatment program. Based on results from the industrial water softening survey, 17 percent (5,860 lb/day) of salts come from water softening activities. The remaining 28,613 lb/day is due to other industrial processes. In 2007, potential water softening commercial entities such as car washes, restaurants and hotels used 4.3 MGD. Assuming an average of 87 percent water returned to the sewer, and 50 percent of the restaurants using SRWS, 2.9 MGD would be softened water. Assuming a source water of 12 gpg and softener efficiencies based on scenarios described in Table 2.14, estimated maximum salt usage was 15,870 lbs/day. The combination of scenarios describing the salt efficiency for SRWS in use for residential and commercial is summarized as a low salt efficiency (maximum salt from softeners) and high salt efficiency (minimum salt from softeners) in Table Based on the average influent TDS for 23rd Avenue WWTP, the salt load is estimated at 411,471 lb/day. The difference between the salt load for 23rd Avenue WWTP and the modeled salts was applied to the Unknown, which make up undetermined sources of salts such as other commercial and industrial (8,322 15,452 lb/day). The results indicate that softening activities account for 8 to 10 percent of the total salts in the 23rd Avenue WWTP sewershed (Figure 2.7). Salts from the source water represent 49 percent of the total salt load. Table 2.16 Salt sources for the 23rd Avenue WWTP sewershed Salt Softening Other Other Efficiency Res Com Indus 4 Res Indus Unknown 3 Cities Source Total Low 1 17,919 15,870 5,860 42,892 28,613 8,322 92, , ,471 High 2 16,080 10,580 5,860 42,892 28,613 15,452 92, , ,471 All quantities in pounds per day of salt 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program 38 Section 2 TDS Contribution Estimates

47 Low Efficiency Softening scenario - Salt sources High Efficiency Softening scenario - Salt sources Other 19% Softening 10% Other 21% Softening 8% Other Cities 22% Source 49% Other Cities 22% Source 49% Figure 2.6 Percentage of salts, by source, in 23rd Avenue WWTP sewershed st Avenue WWTP In 2007, 91st Avenue WWTP received on average 47 MGD from other cities including Scottsdale, Glendale, Tempe and Mesa with a TDS of about 1,000 mg/l or 391,467 lb/day of salts (COP, 2008). There are approximately 294,518 single family dwelling units in Phoenix that discharge into the 91st Avenue WWTP sewershed. Using the penetration data from the Reclamation survey and SRWS efficiency scenarios indicated in Table 2.16, between 73,498 and 81,916 lb/day of salt is added to the 91st Avenue WWTP sewershed from residential water softening. For modeling purposes, it was assumed that the 23rd Avenue WWTP sewershed received 60 percent of the industrial discharges from the pretreatment program. Based on results from the industrial water softening survey, it is estimated that 8,791 lb/day of salts come from water softening activities. The remaining 42,919 lb/day is from other industrial processes. In 2007, potential water softening commercial entities such as car washes, restaurants and hotels used 5.75 MGD. Assuming an average of 87 percent water returned to the sewer, and 50 percent of the restaurants using SRWS, 3.64 MGD would be softened water. Assuming a source water of 12 gpg and softener efficiencies based on scenarios described in Table 2.14, estimated maximum salt usage was 19,879 lbs/day. The combination of scenarios describing the salt efficiency for SRWS in use for residential and commercial is summarized as a low salt efficiency (maximum salt from softeners) and high salt efficiency (minimum salt from softeners) in the following table. Based on the average influent TDS for 91st Avenue WWTP, the salt load is 1.16 million lb/day. The difference between the salt load for 91st Avenue WWTP and the modeled salts was applied to the Unknown which make up undetermined sources of salts such as 39 Section 2 TDS Contribution Estimates

48 other commercial and industrial (17,840 32,884 lb/day). The results indicate that softening activities account for 8 to 10 percent of the total salts in the 91st Avenue WWTP sewershed (Figure 2.8). Salts from source water represent 40 percent of the total salt load and salts from other cities represent 34 percent of the total salt load. Table 2.17 Salt sources for the 91st Avenue WWTP sewershed Salt Softening Other Other Res Com Indus 4 Res Indus Unknown 3 Cities Source Total Low 1 81,916 19,879 8, ,694 42,919 17, , ,922 1,161,428 High 2 73,498 13,253 8, ,694 42,919 32, , ,922 1,161,428 All quantities in pounds per day of salt 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program Low Efficiency Softening scenario - Salt sources High Efficiency Softening scenario - Salt sources Other 17% Softening 10% Other 18% Softening 8% Other Cities 34% Source 39% Other Cities 34% Source 40% Figure 2.7 Percentage of salts, by source, in 91st Avenue WWTP sewershed Cave Creek WRP The Cave Creek Water Reclamation Plant (CCWRP) collects wastewater from an area of 55 mi 2 and is divided into the Cave Creek sewershed and the Mayo Boulevard sewershed. The CCWRP receives an average of 4.4 MGD of wastewater; 75 percent from residential and 25 percent commercial (Phoenix, 2008). The Union Hills WTP provides most of the potable water to the service area. There are approximately 20,809 single family dwelling units that discharge into the CCWRP sewershed. The TNT study indicated that possibly 61 percent of the homes in the sewershed had water softeners (TNT, 2006); however, the Reclamation survey estimates that 49 percent of the homes are using water softeners. Using the penetration data from the Reclamation survey and SRWS efficiency scenarios indicated in Table 2.13, between 7,985 and 8,900 lb/day of salt is added to the CCWRP sewershed from 40 Section 2 TDS Contribution Estimates

49 residential water softening; representing 19 to 22 percent of the total salts in the CCWRP waste stream. There is no industrial sector in the CCWRP sewershed; however, commercial water demand and salt addition can be significant. In 2007, potential water softening commercial entities such as car washes, restaurants and hotels used 0.48 MGD. Assuming an average of 87 percent water returned to the sewer, and 50 percent of the restaurants using SRWS, MGD would be softened water. Assuming a source water of 12 gpg and softener efficiencies based on scenarios described in Table 2.14, estimated maximum salt usage was 1,733 lbs/day, less than the estimate of the 6 major locations in the TNT study (2,263 lb/day). The combination of scenarios describing the salt efficiency for SRWS in use for residential and commercial is summarized as a low salt efficiency (maximum salt from softeners) and high salt efficiency (minimum salt from softeners) in Table Based on the average influent TDS for CCWRP, the salt load is 43,941 lb/day; however, the modeling results for salts added due to softening activities and other residential and commercial uses are 1,590 3,084 lb/day higher. The results indicate that softening or other residential salts may be contributing less than previous studies estimated specifically for this sewershed. Assumptions which may be in error include the percentage of residential softeners in the sewershed, the number of people per household, average flow rates from households and the contribution of other salts. In an attempt to reduce total salts in the sewershed, the CCWRP sewershed was alternatively modeled using a total softener penetration of 32 percent, which is the maximum noted in the other two sewersheds (Table 2.12). Table 2.18 indicates results of modeling and the salt balance with the original modeling assumptions. In comparison, Table 2.19 indicates the results with the alternative modeling assumptions to correct the salt balance. Table 2.18 Salt sources for the CCWRP sewershed Salt Softening Other Efficiency Res Com Indus 4 Res Indus Unknown 3 Other Cities Source Total Low 1 8,900 1, , ,852 44,220 High 2 7,985 1, , ,852 42,726 All quantities in pounds per day of salt 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program 41 Section 2 TDS Contribution Estimates

50 Table 2.19 Salt sources based on alternative modeling assumptions for CCWRP sewershed Salt Softening Other Efficiency Res Com Indus 4 Res Indus Unknown 3 Other Cities Source Total Low 1 5,789 1, , ,852 41,136 High 2 5,195 1, , , ,852 41,136 All quantities in pounds per day of salt 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program The results from the two modeling approaches for CCWRP are significantly different as indicated in Figure 2.9. Further investigation is required to determine the correct modeling approach for this sewershed. Low Efficiency Softening scenario - Salt sources Low Efficiency Softening scenario - Salt sources Alternative Modeling Assumptions Other 22% Softening 24% Other 24% Softening 18% Source 54% Source 58% Figure 2.8 Percentage of salts by source in CCWRP for both modeling assumptions 2.6 Summary Based on modeling assumptions, between 137,202 and 160,869 lbs per day of salt are added to Phoenix sewers from water softening activities in the residential, commercial and industrial sectors. Section summarizes the estimated salt sources by sewershed for both low and high salt efficiency scenarios. The 23rd Avenue and 91st Avenue WWTP sewersheds salt sources add up to the measured total salts in each sewershed. However, the CCWRP salt sources are up to 3,084 lbs/day higher than what has been measured as influent into the plant, indicating that assumptions for this sewershed may not be accurate for the low efficiency softener scenario. Using the alternative modeling assumptions for CCWRP as described in Section 2.5.3, salt sources are balanced with the measured TDS load for the sewersheds Table Section 2 TDS Contribution Estimates

51 Salt Efficiency Low 1 Table 2.20 Total salt balance for Phoenix sewersheds Salt Balance Sewer Softening Other Other Measured shed Res Com Indus 4 Res Indus Unknown 3 Cities Source Total Total Difference CCWRP 8,900 1, , ,852 44,220 41,136-3,084 23rd Ave 17,919 15,870 5,860 42,892 28,613 8,322 92, , , , st Ave 81,916 19,879 8, ,694 42,919 17, , ,922 1,161,428 1,161,428 0 Total 108,735 37,482 14, ,319 71,532 26, , ,270 1,617,119 1,614,035-3,084 CCWRP 7,985 1, , ,852 42,726 41,136-1,590 23rd Ave 16,080 10,580 5,860 42,892 28,613 15,452 92, , , ,471 0 High 2 91st Ave 73,498 13,253 8, ,694 42,919 32, , ,922 1,161,428 1,161,428 0 Total 97,562 24,988 14, ,319 71,532 48, , ,270 1,615,625 1,614,035-1,590 All quantities in lb/day 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program Table 2.21 Total salt balance for Phoenix using alternative modeling assumptions for CCWRP sewershed Salt Efficiency Low 1 Salt Balance Sewer Softening Other Other Measured shed Res Com Indus 4 Res Indus Unknown 3 Cities Source Total Total Difference CCWRP 5,789 1, , ,852 41,136 41, rd Ave 17,919 15,870 5,860 42,892 28,613 8,322 92, , , , st Ave 81,916 19,879 8, ,694 42,919 17, , ,922 1,161,428 1,161,428 0 Total 105,624 37,482 14, ,319 71,532 26, , ,270 1,614,035 1,614,035 0 CCWRP 5,195 1, , ,200 23,852 41,136 41, rd Ave 16,080 10,580 5,860 42,892 28,613 15,452 92, , , ,471 0 High 2 91st Ave 73,498 13,253 8, ,694 42,919 32, , ,922 1,161,428 1,161,428 0 Total 94,773 24,988 14, ,319 71,532 49, , ,270 1,614,035 1,614,035 0 All quantities in lb/day 1 - Based on maximum salts from residential and commercial softening scenarios 2 - Based on minimum salts from residential and commercial softening scenarios 3 - Undetermined sources of salts that balance the total salts with what has been measured 4 - For industries in the Pretreatment program 43 Section 2 TDS Contribution Estimates

52 Modeling of salts using the described assumptions results in 8 to 10 percent TDS contribution from SRWS from all sectors. Source water contributes 42 percent of all TDS in the sewershed. Other salt sources include the other SROG cities discharging into 91st Avenue WWTP and industrial, commercial and residential non-softening uses of water (Figure 2.10). Low Efficiency Softener Scenario High Efficiency Softener Scenario Other 22% Softening 10% Other 19% Softening 8% Other Cities 30% Source 42% Other Cities 30% Source 42% Figure 2.9 Phoenix salt sources Figure 2.11 displays the salt rate from residential, commercial, industrial, SROG influent and source water and compares to each sewershed. 500, , , ,000 Salt [lb/day] 300, , , ,000 Residential Com/Indus Source Other Cities 100,000 50,000 0 CCWRP 23rd Ave 91st Ave Sewershed Figure 2.10 Salt source, by sewershed 44 Section 2 TDS Contribution Estimates

53 Figure 2.12 displays the salt balance for each of the sewersheds as a percentage of the total. The cross hatched regions represent salts originating from water softening activities in each of the sectors. Salt [lb/day] 100% 90% 80% 70% 60% 50% 40% 30% 20% 1,733 8,900 9,733 23,852 15,870 17,919 42,892 92, ,495 5,860 19,879 81, , , ,922 8,791 Indus Soft Com Soft Res Soft Com/Indus Other Res Other Other Cities Source 10% 0% CCWRP 23rd Ave 91st Ave Sewershed Figure 2.11 Detailed salt sources, by sewershed The estimated TDS for the influent to each of the wastewater treatment plants without water softening activities is indicated in Table 2.22 resulting in a reduction of TDS by approximately 100 mg/l from existing concentrations (based on low efficiency scenarios). Sewershed Table 2.22 TDS and salts in sewershed without softening Current Current Total Nonsoftening Resulting TDS Flow salts TDS [mg/l] [MGD] [lb/day] [mg/l] CCWRP 1, , % 23rd Ave 1, , % 91st Ave 1, ,050, % Note: Assumes no change in other SROG cities influent. Assumes same flows to sewersheds. % reduction 2.7 Conclusions Based on TDS and flow data for 2007, more than 1.61 million pounds of salt passed through the City s WWTP. The Phoenix water supply imports much of the salts into the system representing 42 percent of the total salts. Other salt sources are from residential, commercial and industrial activities that result in wastewater discharges into the sewershed. 45 Section 2 TDS Contribution Estimates

54 After review of previous studies, the development of new data from surveys, and modeling scenarios, it is estimated that 8 to 10 percent of the total salts are attributable to water softening activities from residential, commercial and industrial sector. There is some uncertainty associated with this estimate due to the number of assumptions that were required to develop the model. In reality, it is very difficult to project how many softeners are in use in the sewershed since there is tremendous variability in efficiencies and operation. It was assumed that the Reclamation survey represented the best data for determining water softener penetration in the sewershed. Modeling results for 23rd Avenue and 91st Avenue appear to validate the Reclamation water softener penetration values based on age of household. Other assumptions including people per household, wastewater flow rates from commercial, and source water TDS are included in Appendix A. Improvements could be made to this estimate by the following: Verifying average source water TDS and hardness for each sewershed Surveying commercial sector for information regarding water softening activities Additional sampling and analysis of wastewater from residential and commercial sectors. Identifying appropriate assumptions for the CCWRP sewershed. 46 Section 2 TDS Contribution Estimates

55 2.8 References AWWA Research Foundation Characterizing and Managing Salinity Loadings in Reclaimed Water Systems. Number Central Arizona Salinity Study (CASS). September Phase II. Salinity Control at Wastewater Treatment Plants. Retrieved from: City of Phoenix data. Industrial flow and TDS from 2007 Pretreatment participants. City of Phoenix data. Flow and TDS for metering stations ( ). Frost, Doug. City of Phoenix. Correspondence 11/17/08. Jensen, Martin. Rayne Corporation, Phoenix. Correspondence 11/12/2008. Lopez, Gustavo. Greeley & Hansen. Interview 12/13/08. Mayer, P.W., W.B. DeOreo, E.M. Opitz, J.C. Kiefer, W.Y. Davis, B. Dziegielewski, and J.O. Nelson Residential End Uses of Water. Report to AWWA Research Foundation and American Water Works Association (AWWA), Denver, CO. Oberhamer, Doug. Culligan Water Conditioning, Phoenix. Correspondence 11/3/2008. PBS&J Future With No Action. Santa Clarita Valley Joint Sewerage System (SCVJSS) Chloride Source Report. October Sanitation Districts of Los Angeles County. TNT Technology Company. February 24, CASS / Cave Creek Water Reclamation Salinity Study. U.S. Bureau of Reclamation. November 11, Survey of Water Softener Penetration Into the Residential Market in the Phoenix Metropolitan Area. Insights & Solutions. 47 Section 2 TDS Contribution Estimates

56 THIS PAGE INTENTIONALLY LEFT BLANK. 48 Section 2 TDS Contribution Estimates

57 3 TDS Control Programs 3.1 Description The City is interested to know what other municipalities and utilities are doing to control Total Dissolved Solids (TDS) discharges from point-of-use water softening systems into sanitary sewer systems. In preparation for possible TDS control, the City retained HDR to collect information on existing programs developed by other communities to deal with this issue. Such programs range from educational efforts, to incentive payments, to outright prohibition or bans. HDR interviewed industry experts and conducted an internet search to determine which municipalities and utilities have developed information, programs, or policies regarding these types of discharges. The Table of Programs in Appendix M is provided that summarizes the following information by municipality, utility, or agency: Public information and education programs Website addresses Policies, ordinances, and regulations Procedures and prohibitions Exchange or rebate programs Alternatives recommended In addition, data gaps which may be relevant to the City are discussed in this section. Recommendations for subject matter that should be considered by the City for inclusion in information, programs, or policies that may be developed are provided in Section Drivers The two primary drivers for TDS control are water reuse needs and discharge water quality limitations. Depending on the plant variety, turf facilities and agricultural operations can use reclaimed water with a TDS concentration at or below 1200 mg/l with minimal negative effects. Negative impacts have been observed above this concentration and include poor crop performance and the need to use larger volumes of water to leach accumulated salts from the root zone. In addition to the issues associated with elevated TDS concentrations, individual water quality parameters can also present difficulties. Specifically, high concentrations of sodium or chloride can negatively impact users of reclaimed water and potentially impact aquatic species in receiving waters. Surface water discharge permit limitations are often designed to be protective of downstream reuse needs in addition to aquatic life. 3.3 Methods HDR performed this task largely through internet research and interviews with water industry professionals. Several previous studies were reviewed and specific leads were 49 Section 3 TDS Control Programs

58 followed to generate a list of water softening regulatory programs in the United States. In addition, a meeting was held with two local water softener vendors and the Director of Governmental Affairs and Communications for the Water Quality Association (WQA). These industry representatives provided additional information on existing programs. While the information presented in this report covers a large number of existing salinity management programs, it is likely that further research would identify additional examples. Salinity management is a concern for many municipalities in the United States, so it is anticipated that additional programs will develop in the future. 3.4 TDS Control Programs Source waters containing high levels of calcium and magnesium are referred to as hard water. Hard water can cause scale formation of calcium carbonate in hot water heaters, sinks, and toilets; limit soap effectiveness; and affect the taste of the water. Water softening takes the hard minerals out of the water through an ion exchange process by replacing them with sodium or potassium and chloride. Residential water softening is a major industry in the US due to the perceived benefits of soft water over hard water. Arizona is no exception. Source waters available to central Arizona are classified as hard and water customers have often exercised the option to install a water softener to reduce the impacts of hard water in the household. However, water softening has become so prevalent that most new residential developments offer water softening systems as a standard option. Water softener ion exchange resins must be regenerated regularly to operate correctly. This regeneration process results in a highly saline brine of sodium chloride or potassium chloride being discharged directly to the sanitary sewer system or individual septic system, increasing the TDS in the wastewater stream. TDS is commonly referred to as salinity and is approximated by the amount of inorganic salts (calcium, magnesium, potassium, chloride, sulfates, and bicarbonate) and organic solutes. Hardness is a component of TDS. Treating calcium and magnesium hardness by ion exchange increases the overall TDS of the wastewater stream associated with water use. In addition to residential softening, industrial and commercial facilities are also significant users of water softeners. Hotel and resort properties, restaurants, and laundromats regularly utilize water softeners to reduce the impacts of hard water on their operations. It is not uncommon for industrial facilities to treat the municipal water they receive to improve their manufacturing processes. The ultimate result of the increased use of water softeners is an increase in the TDS loading to the wastewater stream. Increased TDS loading can impact wastewater system operations, reuse customers, and receiving waters. The discharge of higher concentrations of TDS or individual constituents such as sodium and chloride has led many communities to enact salinity management programs. The majority of programs that focus on TDS control regulate brine discharges from self regenerating water softeners (SRWS) into septic tanks. There is a continuing debate about the effect of SRWS discharges on the 50 Section 3 TDS Control Programs

59 biological function and the hydraulic loading of septic tanks, as well as the impacts to soils in leach fields. Studies indicate that self-regenerating home water softeners can represent half of the residential wastewater TDS above source water concentrations. The use of in-home water softeners has grown significantly over the past two decades. The water softener penetration in the Phoenix area has increased from 27 percent in the 1980s to approximately 51 percent for homes built after 2000 (Reclamation, 2004). The TDS load that enters the sewer system from residential SRWS is a significant concern to the City. Many other communities that share this concern have taken steps toward managing the TDS loading from residential SRWS. The most active location for TDS management efforts has been California a detailed discussion of in-home softener regulation in that state is provided in Section The regulation of SRWS brine discharges to septic tanks and sewer systems are discussed in Sections and 3.4.3, respectively. An overview discussion of representative salinity management program elements is presented in Section California The State of California has the longest, and perhaps most controversial, history in dealing with water softener regulation. In 1961, Los Angeles County Sanitation Districts No. 26 and No. 32 adopted resolutions that prohibited the discharge of regeneration brines from SRWS. This prohibition applied to residential, commercial, and industrial softening systems. The driver for the prohibitions was to protect the quality of water discharged to the Santa Clara River and preserve the water supply for agricultural reuse. In 1966, the Irvine Ranch Water District enacted its own ban on SRWS to provide adequate water quality for agricultural and turf irrigation reuse. In the 1970s, the California Health and Safety Code provided a series of technical standards for SRWS installed in the State due to growing concerns over the potential impacts of SRWS. However, opposition to the regulatory actions being taken by local communities was also mounting. As a result of opposition efforts, Senate Bill 2148 was passed in 1978 that reversed the local SRWS bans that had been developing in the State. The regulatory framework for SRWS systems evolved through the next several years with the development of Health and Safety Code Sections and These Sections required specific salt efficiency ratings for residential SRWS and requirements for timer or demand-based regeneration. In the mid-1990s, the California Appeals Courts made several significant rulings that restricted the ability of local agencies from enacting ordinances to ban or restrict residential SRWS. In each case, the Courts ruled that ordinances prohibiting residential SRWS systems were invalid because State statues were in place that regulated softener performance (SCVJSS, 2002). 51 Section 3 TDS Control Programs

60 To provide some measure of local control, the California Health and Safety Code (Section ) was amended by Senate Bill 1006 to establish conditions under which a local agency could regulate SRWS. Further changes resulted from the passage of Assembly Bill 334. These legislative actions have set the current form of the California Health and Safety Code related to water softeners. As of mid-2008, a local agency has the right to limit the availability, or prohibit the installation, of residential water softeners that discharge to the sewer system if both of the following conditions apply: 1) Limiting the availability or prohibiting the installation, of the appliances is a necessary means of achieving compliance with discharge requirements or master reclamation permit issued by a regional water quality control board; and 2) The local agency has adopted and is enforcing regulatory requirements that limit the volumes and concentrations of saline discharges from non-residential sources to the sewer system to the extent technologically and economically feasible. The above findings must be substantiated by an independent study that quantifies all sources of salinity including residential water softening, residential consumptive use, industrial and commercial discharges, and seawater/brackish water flows into the sewer collection system. The study must also identify remedial actions taken to reduce the discharge of salinity into the sewer system from each source, to the extent technologically and economically feasible, to bring the local agency into compliance with its permit requirements. These regulations went into effect on January 1, The regulatory framework for SRWS in California continues to evolve. The California legislature passed a measure in August 2008 that would have further refined how SRWS could be regulated in the State. This most recent measure, Assembly Bill 2270, was vetoed by the Governor in September A successful campaign against the Bill ( was launched by the Water Quality Association (WQA). Local entities will continue to seek to increase their ability to manage salinity in their service areas while representatives of the softening industry will fight increased regulation Discharge to Septic Tanks There are a number of states and local communities that have enacted some form of residential water softener regulations. In most states, the regulations have targeted the discharge of water softener regenerate to on-site septic tanks. According to a press release issued in 2002, the following states had enacted, or intended to enact, bans on the discharge of SRWS brine to septic systems: Texas, Washington, Oregon, Nevada, Idaho, California, Missouri, Illinois, Florida, Louisiana, Maine, New York, New Jersey, Tennessee, Kentucky, North Carolina, South Carolina, North Dakota, South Dakota, and Indiana (PR Web, 2008). Research conducted under this Task indicated that there are three key drivers that lead various locations to regulate SRWS discharges to septic systems: 52 Section 3 TDS Control Programs

61 1) The high salt concentrations in SRWS discharges could be harmful to the biological function of septic tanks; 2) SRWS regeneration discharges increase the hydraulic burden on the septic tank and could alter performance; and 3) The salt load of SRWS discharges could alter the soil chemistry of the leach field and negatively affect treatment capacity. Based on these presumptions and the field experience of septic tank installers in many regions, several states have enacted regulations or policies that prohibit the connection of SRWS to on-site septic systems. In most instances, the SRWS discharges are recommended to bypass the septic tank and discharge to a separate drywell. In response to the growing popularity of such regulations, industry representatives commissioned two studies in the late 1970s. The studies were conducted by the National Sanitation Foundation (now NSF International) and the University of Wisconsin- Madison. These studies concluded that no deleterious relationship existed between SRWS discharges and septic tank performance; however, these studies did not put the issue to rest (Bruursema, 2005). The limited scope of these studies and the practical firsthand observations of many septic tank installers contribute to the continuing debate. While many states have regulations in effect that ban the discharge of SRWS regenerate to on-site septic systems, some have reversed their thinking. New Jersey rescinded its ban and Kentucky decided to hold off on enacting its own ban in the face of the pending opposition from the softener industry (McKenzie, 2005). Of special interest, the State of Pennsylvania Department of Environmental Protection has issued an order that SRWS discharges must go to the treatment tank, not directly to the ground or waters of the State. The debate continues to determine whether SWRS discharges negatively affect septic tank operation. Further, different states have conflicting and/or frequently changing guidance on this issue. Due to the relatively small number of septic tanks that are present within the City s water service area, the discharge of SRWS brine to septic systems in not a priority issue for the City. In the event that the City or other local jurisdictions wish to pursue this issue as part of their salinity management efforts, further review of the existing studies and perhaps the initiation of new research in the Phoenix metropolitan area would be warranted before any conclusive course of action can be recommended Discharge to Sewer Systems California s history with water softening regulations demonstrates the difficulty in limiting residential water softening through bans. However, limiting industrial water softening typically generates less opposition. One avenue of regulation is the National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act. NPDES protects water quality in receiving surface waters from point and nonpoint pollution sources. The NPDES permit allows utilities to establish local limits to control 53 Section 3 TDS Control Programs

62 constituents of concern, including TDS. The NPDES pretreatment program attempts to accomplish the protection of wastewater treatment plants and receiving waters through the regulation of industrial sources of discharge. Most utilities operate a pretreatment program but not all are concerned about TDS. Brine discharges from industrial water softening are prohibited through the pretreatment programs for Monterey Regional Water Pollution Agency (MRWPA) and Irvine Ranch Water District (IRWD) (AwwaRF, 2006). El Paso Water Utilities has a TDS discharge limit of 6140 mg/l regulated through the NPDES pretreatment program. The Inland Empire Utilities Agency (IEUA) set a 550 mg/l limit on TDS for discharges from wastewater treatment plants through the NPDES which provides a controlling point for reducing salinity impacts to the Chino groundwater basin (IEUA, 2006). States are also required to adopt surface water quality standards called Total Maximum Daily Loads (TMDLs) that protect impaired waterways from specific pollutants. TMDLs determine the total amount of a specific pollutant the waterway can receive and still meet the water quality standard. In the case of Santa Clarita Valley, chloride was the TMDL which drove the salinity management program. The chloride limit for industrial dischargers is either 100 mg/l or an individual limit determined based on technical and economic feasibility Salinity Management Program Descriptions The impacts of increasing salinity on local water resources have become a popular topic of conversation for water managers. Several local and state-level jurisdictions have taken steps to begin managing salinity impacts. Actions include providing public education, establishing standards, encouraging equipment upgrades, setting NPDES pre-treatment limits, offering rebate incentives to reduce saline discharges, and regulatory bans on the use of softening devices. A general discussion of each of these salinity management program elements is provided in this section. Additional details specific to state and local programs are provided in the Table of Programs in Appendix M. Public Education. Actions to manage salinity impacts begin with a public education program. Water softening activities that rely on ion exchange technologies are a frequent target of such campaigns. Significant salt discharge reductions can be achieved simply by ensuring that the equipment being used by residential, commercial, and industrial customers is properly installed and operated. Communicating best management practices and the consequences to the environment of poor practices should serve as a common element to any comprehensive salinity management program. The Santa Clarita Valley Sanitation District (SCVSD) engages in a very proactive public education campaign as part of its ongoing salinity management activities. The SCVSD worked directly with developers, plumbers, contractors, water conditioning companies, County and City officials, and realtors to communicate the goals and requirements of its program. Information was provided through the internet, brochures, and residential mass mailings. A copy of the Executive Summary of SCVSD s November 2008 report on their outreach efforts is included as Appendix F. The SCVSD program has set the current standard for implementing education as a keystone of a salinity management program. 54 Section 3 TDS Control Programs

63 Standards. California has established an efficiency standard of 4,000 grains of hardness per pound (grains/lb) of regenerate salt used for residential water softening units (Health and Safety Code Sections and ). This standard could only be met by the highest efficiency water softening units on the market. Most certification agencies or laboratories such as NSF or WQA Gold Seal program require salt efficiency of 3,350 grains / lb of salt. No other state has followed California s example for establishing an efficiency standard for residential SRWS. A copy of California Health and Safety Code Sections through is included as Appendix G. Equipment upgrade. Upgrading equipment can offer significant salt and water savings, reducing TDS produced from residential, commercial and industrial water softeners. This program component works well with a water softener efficiency campaign that educates about softening efficiencies and may offer rebates to customers that upgrade to more efficient technologies such as demand controlled regeneration. Geneva, Wisconsin worked with Culligan to provide operational inspections of residential water softeners and adjust for maximum operational efficiencies (Rust, 1997). Culligan of Phoenix has initiated a program independently called Green Solutions 3 Step Plan to inspect their customers water softening equipment to make it more efficient. Pretreatment Limits. As described in Section 3.4.3, utilities implement NPDES pretreatment programs to control TDS at locations that discharge into the sewer and for discharge from wastewater treatment plants. This control only applies to industrial and commercial water softening. Rebates. Three communities in California have offered a financial incentive to improve or eliminate residential water softeners. More information on these rebate programs is included in Appendix H. The Santa Clara Valley Water District obtained grant funding to help pay for a pilot water softener rebate program. Goals of the program were to quantify the water savings, quantify the reduction in salt loading to improve recycled water quality, and increase the local market for recycled water. The pilot program was limited to 400 rebates and consisted of providing a $150 rebate to single-family homeowners that replaced a timerbased softener with a demand initiated regeneration (DIR) unit. In addition, the district has initiated a commercial water softener rebate program to rebate business owners who upgrade timer controlled softener to DIR softeners. The rebate is $400 per owner. The Water Resources Association San Benito County (WRASBC) offers a tiered rebate program to its customers that live in the City of Hollister, the City of San Juan Bautista, the Sunnyslope County Water District, and the San Benito County Water District (Zone 6 only). This program offers a $150 rebate to replace a water softener with a DIR unit, $250 to convert to an offsite regeneration service, or $300 to remove the softener with no replacement. The program applies to softeners installed prior to November Section 3 TDS Control Programs

64 The SCVSD offers a rebate to remove in-home softeners based on reasonable value, removal, and disposal costs. The value is based on the original purchase price and age of the unit. Customers must use a qualified vendor to remove the softener. The rebate applies only to sodium chloride or potassium chloride softeners, not to off-site regeneration units or reverse osmosis (RO) units. The value of the rebate ranges from $275 to $2000. Bans. Actions to ban the use of water softening equipment tend to receive much attention and controversy. A brief review of several internet articles about water softener bans can lead some to think that such actions are quite common and widespread in the US. Upon further review, however, it becomes clear that not all bans are created equal. With respect to water softeners, the most common type of ban is a prohibition of the discharge from SRWS to on-site septic systems. This issue has been the subject of much debate and is discussed in detail in Section of this memo. While discussion of this issue continues in the water community, it is of limited import to the City. The more relevant potential regulatory action for the City is the potential to ban the use of SRWS that discharge to the City s sewer system. This type of ban has largely been limited to communities in California. The ability of California water agencies to regulate the installation of SRWS has evolved over time through lawmaking, court decisions, and significant opposition from the water softening industry. Presently, the SCVSD serves as the most well developed salinity management program, with a ban on SRWS as an integral part. 3.5 Data Gaps Data collected was based on internet research and limited discussions with water and softener industry representatives. While it is likely that other regulatory programs and outreach efforts would be uncovered by additional effort, it is also likely that such additional work would not significantly add to the body of knowledge collected. Rather, it is recommended that direct contacts be made with selected state and local agencies to discuss their salinity management programs. The lessons learned from the previous efforts would be most useful to the City as it moves forward. In addition, if the City decides to move forward with regulations that could impact the installation of water softening equipment in the City, it is clear that the sound justification for such actions must be developed and documented. This will require that the City collect sufficient data on the costs and benefits of any proposed regulatory action and the range of alternative actions that were also considered by the City. 3.6 Summary and Recommendations Water softener discharges have been the subject of debate in several communities over the past few decades. Efforts to manage or regulate these discharges have varied from outright bans to educational programs. By far, the most common issue is the discharge of brine to on-site septic systems. Increasing attention has recently been paid to 56 Section 3 TDS Control Programs

65 industrial/commercial and residential discharges to sewer systems. The most recent activity has been in the State of California. A preliminary review of the regulatory programs implemented by other communities yields the following recommendations for the City as it considers options for its future management and regulatory program: Be transparent and work closely with stakeholders including the Water Quality Association (WQA) and homebuilders. Any initiative that would impact the watersoftening industry in Phoenix will be a significant cause for concern to the local businesses that install softening systems. The WQA and some of its local constituents have stated a willingness to work with the City to develop a salinity management program. They have also demonstrated an aggressive track record of challenging regulatory programs that impact their interests. Make a strong case for implementing regulatory actions that are deemed necessary. Specify the regulatory or management driver that creates the need for the program. The benefits of any regulatory program must be clearly presented so that the impacts to the water softening industry (if any) are placed into an appropriate context and so that the City s program can withstand the challenges that might arise. Consider all sources of TDS that could be managed, and make sure the salinity balance is well understood before making conclusions or enacting regulatory measure. Prioritize regulatory actions that will yield the most benefit at the least cost and/or impact to local businesses and residents. Employ multiple strategies as part of a comprehensive salinity management program: o Utilize TMDLs and NPDES permit limits to regulate TDS discharges o Establish a regional efficiency standard for all SRWS o Educate homeowners on best management practices for existing systems o Educate and/or certify operators of commercial/industrial units o Require certifications for system installers o Research new technologies and practices (e.g. off-site regeneration) o Require the use of approved equipment If it is necessary to take action to reduce and/or eliminate water softening activities within the service area be sure to: o Work with industrial, commercial and residential users of SRWS to maximize efficiencies o Take actions to prevent new systems from being installed during new construction o Require system removal upon remodel or resale o Provide incentives/rebates for homeowners to remove existing systems o Ban the use of water softeners as a last resort 57 Section 3 TDS Control Programs

66 Measure the results of the program on a continuous basis. Potentially phase-in more aggressive measures over time as necessary to meet the management objectives. Evaluate alternatives to regulating water softening activities in the service area. One primary alternative would be to perform end-use treatment for reclaimed water distribution and/or discharge. 58 Section 3 TDS Control Programs

67 3.7 References Bassett, Eugene. An Installer s Observation of the Effects of Water Softeners on On-Site Wastewater Systems. NOWRA 2005 Conference presentation. Bruursema, Tom. Water Softeners and Septic Tanks: Are They a Compatible Combination?. NOWRA 2005 Conference presentation. Center for Water Resources Studies. The Effect of Water Softeners on Onsite Wastewater Systems. NOWRA 2005 Conference presentation. City of Corona. Corona Municipal Code Retrieved from de?f=templates$fn=default.htm$3.0$vid=amlegal:corona_ca City of Dixon. Retrieved from El Paso Water Utilities. Harrison, Joseph; Michaud, Charles. Home Water Treatment Systems Discharges to On- Site Wastewater Systems. NOWRA 2005 Conference presentation. Inland Empire Utilities Association. October Salinity Characterization Study for the Carbon Canyon Water Recycling Facility Iowa Department of Natural Resources. Section A: Water Use. Retrieved from Irvine Ranch Water District. What residential customers need to know before installing a water softener. Retrieved from Karajeh and King. A Salinity Management Strategy Water Softener Replacement Rebate Program. Lathrop Municipal Code. Retrieved from McKenzie, 2005 Mercury News. 8/12/08. California bill allows removal of water softeners. Retrieved from Oberhamer, Douglas. DBA Culligan Water Conditioning. correspondence. 8/8/ Section 3 TDS Control Programs

68 Paso Robles. Wastewater division website. PR Web; 2008; Sabrexs EWP System Softens and Purifies Water Without Violating New Texas Ban on Water Softener Waste in Septic Tanks; Rust Environment & Infrastructure. June Lake Geneva Chloride Reduction Pilot Program. Sanitation Districts of Los Angeles County. November Chloride Source Identification / Reduction, Pollution Prevention, and Public Outreach Plan. Santa Clarita Valley Joint Sewerage System (SCVJSS) Chloride Source Report. October Sanitation Districts of Los Angeles County. Santa Paula Times. 8/23/08. Council takes first step to ban salt using water softening systems. Retrieved from Small Flows Quarterly. Fall Water softener backwash and homeowner onsite systems. National Environmental Services Center. State of Maine. Wastewater and Plumbing Control Newsletter. Vol 23. No. 11. March Retrieved from State of Pennsylvania. Valencia Water Company. Vermont Department of Health Section 3 TDS Control Programs

69 4 Alternatives to Point-of-Use Water Softening 4.1 Description As part of the Citywide Water Softener Study, the City asked HDR to research information about alternatives for point of use water softening systems. Information such as technology employed, manufacturer pricing, water and salt use, energy consumption and any advantages or disadvantages are summarized in the following document. 4.2 Self Regenerating Water Softeners Phoenix area water is known to be very hard at grains per gallon (TNT, 2006). One grain per gallon equals 17.1 mg/l of hardness as calcium carbonate. Hardness is a component of TDS that is measured by the amount of calcium and magnesium in the water. Hard water causes scaling of pipes and appliances and can affect the taste and appearance of water. In Phoenix it is estimated that 31 percent of homeowners use a water softener (Reclamation, 2004). Self regenerating water softeners (SWRS) are effective at removing calcium and magnesium ions in the water through an ion exchange process. As water flows through a negatively charged resin bed in the SRWS, positively charged calcium and magnesium ions are attracted to the resin. The hard ions displace weaker positively charged sodium (Na) or potassium (K) ions from the resin bed that are carried by the flow of water to the point of use. Resins must be regenerated to create capacity for the continual removal of magnesium and calcium ions from source waters. Depending on the SRWS technology, this regeneration may occur at a specific frequency or based on volume of water that has passed through the resins. Whichever technology is used, the resin is regenerated using sodium chloride (NaCl) or potassium chloride (KCl) brine solution to flush the resin to replace the calcium and magnesium ions with sodium or potassium ions. The waste water from the regeneration cycle is then discharged directly into the sewer with a very high TDS. Therefore, in the process of reducing hardness of the product water, ion exchange increases TDS in wastewater. 4.3 Hardness and TDS Control Standards There are a number of standards that apply to drinking water devices that control hardness and TDS. NSF/ANSI 44 is the national standard for point of use water softeners which assesses the product s structural integrity, softening performance and capacity. Table 4.1, below, summarizes this standard. Softening performance and capacity is measured through laboratory analysis of the water entering and leaving the softening system. To pass the standard, water softeners are required to remove hardness in a ratio of 20:1 grains per gallon. 61 Section 4 Alternatives to Point-of-Use Water Softening

70 Maximum Contaminant Level (MCL) Potential Problems Potential Source of Contaminant Table 4.1 NSF/ANSI standards for hardness Hardness N/A Applicable NSF/ANSI Standard(s) Standard 44 Can cause scale buildup in appliances and hard water deposits on glass and other surfaces Naturally occurring deposits of calcium and magnesium Water Treatment Technologies Certified by NSF for Reduction of this Contaminant Special Notes Cation Exchange Softener None NSF also has standards specific for reducing TDS. These are specific to filters (NSF/ANSI 42), reverse osmosis drinking water systems (NSF/ANSI 58), and distillation systems (NSF/ANSI 62). NSF testing standards for RO systems require TDS reduction from 750 mg/l to 187 mg/l. Certified distillers reduce TDS from 1000 mg/l to 10 mg/l. Table 4.2, below, summarizes these standards. A list of products that have been certified under these standards is included in Appendix I. The NSF website also evaluates claims for health effects of various drinking water treatment units (NSF 53) Recommended Maximum Level Potential Health Effects (from ingestion of water) Potential Source of Contaminant Applicable NSF/ANSI Standard(s) Table 4.2 NSF/ANSI standards for TDS Total Dissolved Solids (TDS) 500 mg/l Gastrointestinal irritation in some individuals Erosion of naturally occurring mineral deposits Standard 42 Standard 58 Standard 62 Water Treatment Technologies Certified by NSF for Reduction of this Contaminant Special Notes Distillation Reverse Osmosis Products certified for reduction of total dissolved solids will also be effective for reduction of sodium. However, NSF does not have a standard for evaluating hardness removal or scale control for water systems which do not use ion exchange. There are two standards that have been used for evaluating non-softening scale control devices. The International Association of Plumbing and Mechanical Officials (IAPMO) standard AB1953 applies only to the materials and construction of anti-scale or water conditioning devices. The German standard DVGW W512 addresses testing of scale control device in which the water is not chemically altered. In the US however, there is no accepted standard for laboratory testing to evaluate the scale control effectiveness in these devices 62 Section 4 Alternatives to Point-of-Use Water Softening

71 The DVGW W512 is a 21-day test conducted using hard water using four side-by-side plumbing systems with water heaters (two as control and two with the test device). The amount of scale buildup on the heating element is measured for scale removal efficiency. Critics argue that the DVGW W512 test is not sufficient since other parameters affecting scale formation such as flow rate, electrical conductivity, temperature and iron concentrations are not adjusted in the test to evaluate the scale removal efficiency with differing parameters. The Water Quality Association (WQA) provides third-party testing for the point-of-use drinking water treatment industry through the Gold Seal certification program. The Gold Seal identifies product quality which meets certain requirements described through other national standards used for North American point-of-use drinking water industry such as NSF / ANSI, IAMPO, ASTM, and ASME. 4.4 Alternatives to Ion Exchange Water Softening There are a number of alternative processes for ion exchange marketed for reducing hardness or scale control. Many of the products being marketed as alternatives to ion exchange water softeners use one or a combination of processes described in Section 4.6. The products listed in Section 4.6 were assembled from product information sheets from the City, product listings on the Los Angeles County Sanitation District website for ion exchange water softening alternatives and other web based research. These processes are categorized as thermal, physical, electrical, chemical and other. Some of the described alternatives may be a combination of more than one process; however, each is categorized by the major process employed to reduce harness Thermal Distillation is a thermal process that has been used for centuries. The source water is heated to boiling and the steam is collected in a condenser. As the vapor cools, it condenses to water and is collected and stored. Most contaminants remain in the source water vessel while almost pure water is recovered from the condenser. Distillers remove about 99.5 percent of the impurities from the original water (Derickson et al, 1992). Distillation units are designed to operate in a batch process or to provide continuous flow. Distilled water typically has a bland taste due to the absence of minerals. Some products address taste by dripping the condensate over a magnesium mineral to add healthy minerals to the product water. The product water should be stored under sanitary conditions in plastic, glass, or stainless steel containers to prevent bacteria growth. Household distillers are typically designed for providing water for drinking and cooking. It is usually not economical to distill water for other uses like toilet flushing, bathing, and clothes washing. NSF 62 is a standard for drinking water distillation systems. Availability Distillation equipment is readily available in the marketplace. The Dol-Fyn is the only distillation product listed in Section 4.6. In addition there are some distillation devices that have been certified by the NSF standard 62 and are included in Appendix I. 63 Section 4 Alternatives to Point-of-Use Water Softening

72 Costs In-home units range from $1700 to $2190. Advantages Removes a wide range of contaminants in the source water The process does not use chemicals The process does not use parts that foul or require replacement Disadvantages Removes Chlorine residual Requires careful maintenance to maintain water purity Energy intensive Expensive Low flow rates Does not address hardness away from point-of-use Some organic materials enter the vapor stream and can become concentrated in the product water Physical Filtration The process of filtration essentially consists of passing water through a barrier (porous material or membrane) to remove suspended or dissolved particles from the source water. The constituents that are removed depend on the material and pore size of the barrier and the operating pressure of the system. Filtration is widely used in residential water treatment, although not all filtration addresses the issues of TDS or hardness. Many products listed in Section 4.6 use activated carbon adsorption as a filter media to remove taste and odor issues and other organics in the drinking water. This assessment focused on the processes of ultrafiltration and reverse osmosis as these processes could be considered an alternative to self-regenerating ion exchange water softeners. There are some products using filters which have been certified under NSF/ANSI 42 (Appendix I) Ultrafiltration An ultrafiltration membrane separates dissolved molecules on the basis of size by passing a solution through an infinitesimally fine filter. Ultrafilters are available in several selective ranges. In all cases, the membranes will retain most, but not necessarily all, molecules above their rated size. Smaller molecules are allowed to pass through the membrane into the product water. Availability Ultrafiltration equipment is readily available in the marketplace. Products listed in Section 4.6 include: Aquasource, Aqua Vantage, Aquafer Water Source, CleenWater Premium Combo, and DePure EcoPur. 64 Section 4 Alternatives to Point-of-Use Water Softening

73 Costs In-home units range from $1,000 to $5,000 depending on size/flow rate and the other systems that are packaged along with the ultrafiltration unit (carbon filter, etc.). Additional costs include periodic filter replacement. Advantages No ions are added Effectively removes most particles above the rated size. Produces high quality product water Less expensive than Reverse Osmosis Lower energy demand than Reverse Osmosis Rejects less water per gallon than Reverse Osmosis Disadvantages Produces a saline waste product Does not remove dissolved inorganics Can have significant water loss Higher cost than some alternatives Higher energy use than some alternatives Reverse Osmosis Reverse Osmosis (RO) uses a membrane that is semi-permeable to reject most contaminants and produce very high quality water. RO can remove over 90 percent of all contaminants from the source water. The pore structure of RO membranes is much finer than ultrafiltration membranes. In water purification systems, hydraulic pressure is applied to the concentrated solution to counteract the natural osmotic pressure and create a concentration differential across the membrane. Pure water is driven from the concentrated solution and collected downstream of the membrane. NSF 58 is a standard for RO drinking water treatment systems. Availability Reverse Osmosis equipment is readily available in the marketplace. Appendix I lists numerous reverse osmosis drinking water systems that have been certified by the National Sanitation Foundation standard NSF/ANSI 58. Costs. In-home units range from $400 to $5000. Membrane replacements can cost between $60 and $600. Advantages No ions are added Effectively removes most types of contaminants including dissolved inorganics Requires minimal maintenance Produces very high quality water Accepted testing standard to evaluate TDS removal using reverse osmosis 65 Section 4 Alternatives to Point-of-Use Water Softening

74 Disadvantages Produces a highly saline waste product Significant water loss (2-4 gallons/ gallon produced) High cost High energy use Low flow rate Not cost effective for whole house water demands Depressurization Depressurization is a physical process that reduces hardness by rapidly reducing water pressure. Depressurizing allows carbon dioxide to escape such as when carbonated beverages are opened. When the carbon dioxide escapes the carbonates precipitate out as fine particles which are unable to form scale deposits. This is used on deep groundwater but is not applicable for domestic systems Availability. Free-Flo Hard Water Buster Cost - Unknown Advantages No ions are added Disadvantages Carbon dioxide transport between air and water is a slow process Carbon dioxide may be re-dissolved into the water, affecting the water chemistry Manufacturer claims are not supported by scientific technical literature Not applicable for domestic systems No accepted US testing standards Electrical Water is dipolar and can be partially aligned in an electric field. There are a number of devices that take advantage of this in attempt to reduce hardness ions or precipitate in solution to limit scaling. These technologies include magnetic, electromagnetic and electrostatic devices Magnetic Magnets have been promoted since 1930 s to alleviate hardness in water; however, their effectiveness is still debatable. Advertising literature claims magnetic water treatment affects the hardness ions such that scale is easily wiped off or that it precipitates in solution and is carried with the flow of water. There is evidence that magnets have inhibited scaling in some circumstances; however, critics argue that other operating parameters such as flow rate, water chemistry and magnetic field strength have not been clearly defined. Magnetic fields can weaken the attraction or repulsion forces of molecules (van der Waals force). The mechanics of magnetic water treatment are not fully understood. Proponents of magnetic water treatment claim that calcium carbonate 66 Section 4 Alternatives to Point-of-Use Water Softening

75 precipitates as aragonite which is less stable than the calcite structure. Calcite is the stable crystal phase of calcium carbonate and it is reported that it reverts to aragonite at -60 C. According to other scientific tests, aragonite will only form under well defined temperature and pressure conditions. Availability. There are many products promoted as using magnetic water treatment. Some of these use only magnets (Superior Water Conditioner, GMX, Hard Water Wizard, CWS) while others use a combination of activated carbon adsorption for taste and odor control as well as other filtration processes (Aqua Source, Filtercon, Purity 101, Waterboy). Cost. For devices using only magnets, costs range from $500 to $2000. For devices using activated carbon and filters costs can range from $1000 to $5000. Advantages No salts added Can be low cost Magnets do not require electricity Magnets do not require maintenance Disadvantages Magnets are not a proven technology for reducing scale in every situation Lack of credible performance data for many magnetic products Process may be reversible Advertising claims are not scientifically based No accepted US testing standards Electromagnetic Other magnetic devices use an external solenoid coil through which an alternating current passes. The electric field produces a chemical reaction in the ions in the water which precipitate within and are carried along with the water. Studies indicate that the electromagnetic field may create nucleation sites for precipitation of salts (Cho, 2005). There have been some studies that indicate that electromagnetic water treatment can be effective under the right parameters, however those parameters are not well defined. Accepted scientific principles describe carbonate precipitation only when the free carbon dioxide is driven off and the ph is raised. Availability. Electromagnetic equipment is readily available on the market including Scale Watcher, Small Wonder US149 and Soo-Soft Digital Water Softener. Cost. These devices are relatively inexpensive and may cost up to $500. Advantages: No salts are added to the system Improves lathering and other benefits of softer water. 67 Section 4 Alternatives to Point-of-Use Water Softening

76 Can remove existing scale especially where iron is present in the scale Disadvantages: Process may be reversible and unit needs to be fitted close to where scale would form. Engineering studies of actual industrial installations of these products often describe limited effects. (Kiester, 2004). No accepted US testing standards Electrostatic In water treatment facilities, electrolytes such as iron or aluminum salts are added to the water which causes colloidal particles to form together and settle out of suspension in a process called flocculation. Electrostatic fields are also known to affect colloidal or amorphous calcium carbonate particles including algae and bacteria in solution similar to flocculation. Electrostatic fields have been used to remove colloidal particles from settling basins and controlling slime in large cooling systems. Colloidal particles attract a cloud of oppositely charged ions that limit the clustering of the particles. Electrostatic devices control the settling or dispersion of particles with low surface charges. One such product, the ZetaRod, operates as a cylindrical capacitor inside metal piping or vessels to create a static electric field using direct current. The electric field induces alteration of the natural surface charge density of dielectric colloidal particles (Pitts, 1995). However there is not credible evidence that this process can effectively limit scaling (Lower, 2008). Availability. The Zeta Rod is a electrostatic water treatment system. Costs. The price for the Zeta Rod can range from $ $2500. Advantages No salts are added Disadvantages Lack of scientific data to back up marketing claims No accepted US testing standards Electrolysis Electrolysis is the decomposition of water into oxygen and hydrogen gas caused by an electric current applied to the water. Due to safety issues associated with the generation of hydrogen gas, electrolysis is generally reserved for industrial applications. Availability. The list of residential point of use devices listed in Section 4.6 does not include any system that uses electrolysis. Cost. Unknown. 68 Section 4 Alternatives to Point-of-Use Water Softening

77 Advantages Removes impurities No salts are added Disadvantages Dangerous Not effective for scale control No validation of process for scale control in technical literature No accepted US testing standards for this process Capacitive Deionization Capacitive deionization is a new technology that is being developed for desalinating ocean and brackish water. High TDS water is passed between high surface area carbon electrodes with a 1.3 V potential difference. Positively charged ions such as calcium, sodium and magnesium are attracted to the negatively charged electrode while the anions (chloride, nitrate, silica, etc) are attracted to the oppositely charged electrode. The electrodes are regenerated after becoming saturated by removing the electric potential on the electrodes which releases the cations and anions. Generally about 80 percent of the water is deionized while the remaining 20 percent is rejected with the brine. Research continues to improve the electrodes to carry more capacity and reduce the cost. Availability: This process is being applied for point of use residential water treatment through products such as the Judo Biostat 2000, H20 Solutions and Remco. Cost. Unknown Advantages More efficient water use than RO Efficient removal of hardness ions Does not add any salts Disadvantages Current carbon aerogel electrodes are expensive and the ion storage capacity is low. No accepted US testing standards for this process Chemical Catalytic Conditioners Alternatives to ion exchange are often described as physical water conditioners or conditioners. Conditioning does not add any salts into the system but affects calcium and magnesium ions such that they precipitate in solution and not in adherent layers on surfaces. Water conditioning limits scale encrustation by providing nucleation seeds or 69 Section 4 Alternatives to Point-of-Use Water Softening

78 the first tiny crystallite for the formation of calcium or magnesium carbonate in suspension. In suspension, carbonates can not encrust other surfaces such as heating elements and is carried with the flow of water through the system. Catalysts are used to create the nucleation seed affecting the rate of the reaction. In catalytic conditioners, the nucleation seed is created using numerous methods including magnetic / electrolytic, cathodic or electronic / electromagnetic to leach a metal (zinc) into the solution, which attracts the harness ions. Anodes may be fitted inside the water while other devices rely on zinc in the influent water. The process is dependent on flow rate, age of magnets, pipe materials, and concentrations of organics and inorganics in the water. Availability. Catalytic conditioners are represented in products from Environmental Water Systems, Sterling Water Systems, Aquafer Water Source, Safewater softeners, Catalytic 1000, and Ecosolution. Cost. Prices can range from $500 - $3500. Advantages No salt alternative Can be relatively inexpensive Easy to install Disadvantages Inconsistent performances Zinc dosing is not controlled Theory behind the principle may be flawed No accepted US testing standards for this process Epitaxial Crystallization Conditioners A number of water conditioners use special media that act as nucleation sites for calcium and magnesium carbonates. The process sometimes referred to as epitaxial crystallization. Some vendors call this template assisted crystallization. When hard water is in contact with the media, calcium and magnesium carbonates begin to precipitate on the media and move along with the flow of water. The hardness is not removed; however, the hard scaling is limited due to the precipitation in solution. Theory indicates that pretreated water must be supersaturated with calcium and magnesium carbonates to reduce the concentrations to saturation level. At higher temperatures, carbonates will be less soluble. The product Next Scale Stop has received a high efficiency rating from the German standard test. A well known company, Watts, is promoting a product OneFlow that operates in this manner. Availability. Conditioners that use special media for crystallization include Scale Prevention System, DePure EcoPur, and Watts OneFlow. Cost. Prices can range from $ $ Section 4 Alternatives to Point-of-Use Water Softening

79 Advantages No salt alternative Does not require electricity Long lasting media Disadvantages Can not reduce hardness sufficiently to eliminate soap scum or deposits due to evaporation or heat exchanger surfaces Removing calcium and magnesium would create significant solid by product No accepted US testing standards for this process Pellet Softening Hardness can be removed from source waters by the precipitation of crystals in a fluidized bed reactor called a pellet reactor. Sand crystals are used to seed the reactor and provide growth media for calcite crystals to precipitate. The chemistry of a pellet softening process is similar to conventional softening; however, the pellet softening process does not introduce sodium or potassium to precipitate the hardness ions. In addition, the crystallized calcite that is produced through pellet softening can be used in industrial applications (Mahvi et al, 2005). A municipal-scale pellet softening pilot program is underway in the Santa Clarita Valley of California (Slutske, 9/16/06). Availability. It is not clear if this technology is available for in-home use. Locations where it is being piloted are on the neighborhood scale as a source water hardness control option. Cost. Not available. Advantages Pellets can be exchanged while system is in operation The by-product is a marketable commodity Removed hardness without increasing salinity loading Disadvantages Not available for in-home use Costs not yet determined Still in pilot phase Demineralization Demineralization is a hardness removal process that does not use sodium or potassium salts to replace calcium. Rather, calcium ions are replaced with hydrogen ions through the introduction of a weak hydrochloric acid. This process removes the alkalinity associated with hardness (TNT, 2006). Up to one-half of the total hardness of the source water can be removed through demineralization. 71 Section 4 Alternatives to Point-of-Use Water Softening

80 Availability. Demineralization is used only in industrial applications. It is unknown if this process has been attempted for residential application. Cost. Unavailable Advantages Smaller system size. Smaller waste volume than conventional softening. (Generates 1.25 lbs of CaCO 3 per 1,000 gallons treated compared to lbs of CaCO 3 /1000 gallons.) Produces lower salinity brine for sewer discharge than conventional softening. Disadvantages Adds ions to waste water CO 2 that is produced in the process must be removed from the waste brine prior to sewer discharge Safety of chemical handling (hydrochloric acid) Regeneration costs may be higher 4.5 Other Cathodic The Judo Biostat 2000 water treatment system which passed the German W512 standard for hardness control uses an electrical current in the water between an anode and cathode. The anode is a noncorroding, iridium coated titantium wire mesh, and the cathode is stainless steel wire brush. Calcium carbonate is precipitated on the brush when the ph is raised near the cathode. The brush is mechanically cleaned to maintain capacity (Seccombe, 2006). Availability. There are not many effective cathodic devices on the market. The Judo Biostat is not well known in the US. Cost. Unknown Advantages Does not add salts High efficiency rating from DVGW W512 Disadvantages Requires regular maintenance Can be expensive No accepted US testing standards for this process 72 Section 4 Alternatives to Point-of-Use Water Softening

81 4.5.2 Portable Exchange Portable exchange softening uses the traditional ion exchange process; however, the regeneration of resin is completed at a central facility. This is considered an alternative to self regenerating water softeners since brine is not being discharged into the residential sewer. Regeneration can be controlled increasing the salt efficiency of the softeners. Companies involved in portable exchange are considering methods to increase salt efficiencies as well as significantly reduce brine discharges. Availability. Culligan and Rayne have portable exchange tanks for ion exchange water softeners and are able to achieve higher salt efficiencies than some self regenerating water softeners. Costs. Tanks are rented for $50 - $100 per month Advantages Centralized regeneration can be regulated through a pretreatment program Controlled regeneration can increase salt efficiency Low capital cost to user System is managed by the company Disadvantages Adds salts to the sewer system High Efficiency Ion Exchange Due to increasing opposition to the amounts of salts added to the waste stream due to ion exchange water softening, companies are working to improve salt efficiencies in SRWS. Ion exchange is a proven technology for reducing hardness and can be evaluated and certified through NSF. One such approach is to direct hard waters through a number of layers of the resin bed filtering particulates and softening the water through ion exchange. The flow is reversed and pulsed through the multiple layers of resin to regenerate resins reducing salt use by 60 percent, according to marketing literature. There are a number of other schemes which are claimed to improve salt efficiencies; however, the remaining disadvantage to ion exchange is that ions are being added to the water system and will continue to have a negative impact to waste streams. 73 Section 4 Alternatives to Point-of-Use Water Softening

82 4.6 Table of Alternatives Table 4.3 Table of Alternatives 74 Section 4 Alternatives to Point-of-Use Water Softening

83 Table 4.3 Table of Alternatives (continued) 75 Section 4 Alternatives to Point-of-Use Water Softening

84 Table 4.3 Table of Alternatives (continued) 76 Section 4 Alternatives to Point-of-Use Water Softening

85 Table 4.3 Table of Alternatives (continued) 77 Section 4 Alternatives to Point-of-Use Water Softening

86 4.7 Summary There are many products using technologies that may be capable of reducing effects of hardness. However, as noted previously, there are no accepted US standards for testing the hardness mitigating effects of products that do not use ion exchange, distillation, ultrafiltration or reverse osmosis. In addition, most of these products do not provide sufficient technical data to support advertised claims and are marketed based on testimonials not performance data. There are also negative results for some similar products used in industrial applications for controlling scale in cooling structures (Kiester, 2004). Academic research has supported a number of treatments but has not clearly defined the parameters for reproducing results at locations with differing water chemistry and flow rates. The only standard that may be applied for evaluating many of these alternative water treatment devices is the German standard DVGW W512. Table 4.4 summarizes the described processes and the effectiveness at removing hardness, TDS reduction, US standards applicable, scale control and the change in TDS concentration of the water entering the waste stream. Hardness removal only refers to removal of calcium and magnesium ions. There are two processes, ion exchange and demineralization, that actually increase the TDS concentration in the waste stream due to the addition of ions. Distillation and pellet softening have the potential to decrease the TDS concentration entering the waste stream since the calcium carbonates and other salts are removed without adding other ions. The remaining processes do not change the TDS in the waste stream. The table also identifies which processes have NSF/ANSI standards for certifying for TDS or hardness removal. As noted previously, depressurization and demineralization are not for residential uses. Process Table 4.4 Summary of processes used for scale control Hardness Removal TDS Reduction NSF/ANSI Standard Scale Control Change in TDS to WW Ion exchange 95% only Ca, Mg 44 yes increase Distillation 99% 99% 62 yes decrease Ultrafiltration > 75% > 75% 42 yes neutral Reverse Osmosis > 75% > 75% 58 yes neutral Depressurization 2 NA neutral Magnetic 0% 0% unknown neutral Electromagnetic 0% 0% unknown neutral Electrostatic 0% 0% unknown neutral Electrolysis 0% 0% unknown neutral Capacitive Deionization 99% 99% yes neutral Catalytic Conditioners 1 0% 0% yes neutral Pellet Softening only Ca only Ca yes decrease Demineralization 2 < 50% only Ca NA increase 1 A number of catalytic conditioners have been certified by the German DVGW W 512 standard 2 These processes are not applicable for residential systems 78 Section 4 Alternatives to Point-of-Use Water Softening

87 In summary, of the many processes described as potential alternatives for ion exchange SRWS for reducing hardness or effects of hardness, the most reliable processes include reverse osmosis, ultrafiltration, and distillation. Capacitive deionization and catalytic conditioning, specifically, epitaxial crystallization have potential alternatives to ion exchange softening; however additional testing should be performed. A testing method or additional research should be developed to identify the effectiveness of magnetic water treatment for residential hardness control. The technologies of distillation and pellet softening have greatest potential for reducing TDS concentration at the waste water treatment plant. 79 Section 4 Alternatives to Point-of-Use Water Softening

88 4.8 References Andrews, Rick. Non-Softening Scale Control Devices Standards and Lack Thereof. Water Conditioning & Purification. July Cho, Young. Int. Communications in Heat and Mass Transfer 32 (2005) Derickson, R., Bergsrud, F., Seelig, B. Treatment Systems for Household Water Supplies. North Dakota State University. AE April Retrieved from: Dietz, Steven. Improved Electrodes for Capacitive Deionization NSF Design, Service and Manufacturing Grantees Conference. January Kiester, Timothy. Non Chemical Devices: Thirty Years of Myth Busting. Presented at 2004 International Water Conference. Retrieved from: Lower, Stephen. Magnetic Water Treatment. Water Conditioning & Purification. June Mahvi, A. H., F. Shafiee, and K. Naddafi. Feasibility Study of Crystallization Process for Water Softening in a Pellet Reactor. International Journal of Environmental Science & Technology. Winter Pitts, Michael. Fouling Mitigation in Aqueous Systems Using Electrochemical Water Treatment. April retrieved from Seccombe, Johnny. October Fact, Fiction or Fantasy. Water Conditioning and Purification. Slutske, Reina V. Valencia Water to Test Pellet Softening The Signal. 9/16/06. TNT Technology Company. CASS Cave Creek Water Reclamation Salinity Study. February 24, U.S. Bureau of Reclamation. November 11, Survey of Water Softener Penetration Into the Residential Market in the Phoenix Metropolitan Area. Insights & Solutions Section 4 Alternatives to Point-of-Use Water Softening

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90 5 Potential TDS Reduction Program Components 5.1 Description Task 4 of the City of Phoenix (City) Water Softener Study included developing a list and description of program components that could be implemented by the City and regional partners to reduce salt contributions from point-of-use water softening systems. The list of potential program components was derived from the benchmarking activities associated with Task 2 (Research TDS Control Programs) and HDR s assessment of program components that may be appropriate for Phoenix. HDR reviewed existing relevant State regulations and City ordinances and policies to characterize the existing regulatory and authority framework (see Appendix J). Specific policy changes based upon regulatory or authority gaps that exist, or based upon contradictions in existing policies and ordinances, are also recommended. HDR considered the following types of program components: Rebates for removing or exchanging older systems for newer systems that discharge less total dissolved solids (TDS). Ordinances specifying the types of water softener systems that can be installed, or performance and operation standards that must be met for installed systems. Other incentive and dissuasive based components that have been demonstrated to be effective at reducing TDS contributions to wastewater streams from point-ofuse water softeners. This report documents the findings and recommendations for Task Background A salinity management program in the Phoenix area would need to be based upon an assessment of current TDS sources and concentrations and the future water quality target(s). From previous studies, a known source of TDS is point-of-use water softeners. It was therefore necessary to further characterize the TDS contribution from point-of-use water softeners and subsequently identify policies and management methods that could be used to reduce the respective TDS contribution. Coupled with other salinity management program components that address other sources of TDS, the management of point-of-use water softeners could help achieve the overall salinity management program goals. 5.3 Current TDS Conditions Under Task 1 of this study, the City requested HDR to update previous estimates of the contribution of TDS in wastewater from self regenerating water softeners (SRWS). HDR reviewed numerous salinity studies completed in Phoenix and elsewhere to develop an approach for estimating by sewer shed the percentage of TDS in wastewater that is attributable to point-of-use water treatment devices. Previous studies indicated that 26 percent of the TDS in Phoenix-area wastewater is attributable to SRWS discharges. The results of Task 1, however, indicate that the contribution of TDS to Phoenix-area 82 Section 5 Potential TDS Reduction Program Components

91 wastewater treatment plants from water softening is approximately 8 to 10 percent. This value includes commercial and industrial water softening in addition to residential SRWS. 5.4 Desired Future Conditions The USEPA recommends a secondary drinking water standard of 500 mg/l for TDS. This standard is based mainly upon aesthetics; however, the TDS concentration of a community s source water can have long-term potential consequences beyond these aesthetic impacts. In the Phoenix metropolitan area, nearly all of the water imported and diverted for use is fully consumed. Conservative water quality parameters, such as TDS, are left behind in the local soil. Rarely does the Phoenix metropolitan area enjoy the TDS transport and dilution effects of stormwater that is common to other parts of the United States. Essentially, our water management system has established the Phoenix metropolitan area as a salt sink. Therefore, the Phoenix metropolitan area needs to approach setting a TDS concentration goal less based upon drinking water aesthetics, and more based upon the consequences of consumptive use. Two common intermediate drivers for TDS regulation are receiving water quality standards for wastewater treatment plant effluent discharges and water quality requirements associated with beneficial reuse applications of treated wastewater. Water reuse is an important water management strategy for the City to meet current and future water demands. Reclaimed water is used for agriculture, turf irrigation at golf courses and parks, as cooling water for the Palo Verde Nuclear Power Plant, and for groundwater recharge. Water reuse is a primary driver for TDS regulation for the City of Phoenix. Under Task 8A of this study, HDR developed a range of potential long-term TDS concentration goals for reclaimed water produced by the City s various wastewater treatment facilities. These TDS water quality standards will be key elements in finalizing what measures the City must include in its overall salinity management program. To meet the future standard, the City has three main alternatives or a combination: 1) the City can provide source water treatment to reduce salinity prior to the delivery of potable water to customers; 2) the City can implement a salinity management program for users of the potable water system including the regulation of water softening devices; or 3) the City can provide TDS reduction as part of the wastewater treatment process. This technical memorandum focuses on the second option to manage the salinity load that enters the regional wastewater treatment plants. 5.5 Methods of Program Evaluation Task 4 was completed based on an evaluation of the results of Task 2: Research TDS Control Programs and Task 3: Water Softener Alternatives and an assessment of the logical progression of salinity management actions that could be taken to achieve the City s TDS target for reclaimed water. In addition, HDR reviewed the existing state and local institutional framework to determine the adequacy of the various program components and necessary steps to ensure that the City can effectively manage salinity concentrations in the wastewater stream and subsequent reclaimed water resource. 83 Section 5 Potential TDS Reduction Program Components

92 5.6 Potential Program Components Several alternative program components exist that could be implemented by the City to manage the TDS entering the wastewater treatment plants. These components previously described in the Task 2 and 3 reports are summarized and evaluated for their potential suitability for the City of Phoenix in this section Public Education Actions to manage salinity impacts typically begin with a public education program. Significant SRWS salt discharge reductions can be achieved by ensuring that the equipment being used by residential, commercial, and industrial customers is properly installed, operated, and maintained. Communicating best management practices and the consequences to the environment of poor practices should serve as a common element to any comprehensive salinity management program. A public education program should engage the users of the equipment for residential, industrial or commercial softening as well as homebuilders. The educational program should provide information on water softening alternatives that do not increase the TDS load in the sewer shed and are comparable or lower in price than SRWS. This will require that an evaluation be conducted to ensure that the alternative technologies adequately address the consumers hard water concerns and do not create other negative unintended consequences. Several communities have developed public education materials from which the City can draw in developing its own messages. Locally, a public education video was produced as part of the Central Arizona Salinity Study (Salinity: Seeping through the Desert) to provide an overview of salinity issues, which the City has previously aired on their public television channel Standards Under most of the potential salinity management program options available to the City, it is likely that water softening systems will continue to be used in the community at some level. It is advisable to establish minimum performance standards to ensure that the systems that are used in the City are designed, operated, and maintained to be efficient with respect to water and salt usage. Performance standards have been developed for SRWS based on the current level of technology and economic considerations. Such standards have been applied to industry equipment certification programs and by certain communities that regulate the use of SRWS. Examples include the Water Quality Association s Gold Seal equipment certification program and the efficiency standards established in California (see Appendix M). Implementing efficiency standards will help manage the salinity loading that comes from such devices into the future. A complementary measure would be to establish standards or a certification process for water softener installers. The WQA has indicated it is in support of such a certification to protect the quality of the industry. The proper installation of the softening equipment is important to maintain high salt and water efficiencies. 84 Section 5 Potential TDS Reduction Program Components

93 5.6.3 Alternative Technologies There are many products using alternative technologies that may be capable of reducing hardness scaling for the residential sector of the softener market. However, there are no accepted US standards for testing the hardness mitigating effects of products that employ technologies other than ion exchange or reverse osmosis. In addition, most of these products do not provide sufficient technical data to support advertised claims and are marketed based on testimonials and not performance data. Of the many point of use processes described as having the potential to reduce hardness or the effects of hardness, the most reliable processes include reverse osmosis, ultrafiltration, distillation, capacitive deionization, and epitaxial crystallization. Further investigation and testing of alternative technologies could be a part of the City s overall salinity management program. Companies that market portable exchange water softening systems in Phoenix are working to reduce or eliminate brine discharges into the Phoenix sewershed. Portable exchange water softening systems involve the centralized resin regeneration of customer softening systems. The centralized processing of the ion exchange resin results in a brine waste stream that can be more easily controlled and managed Equipment Upgrades Similar to setting appropriate efficiency standards, upgrading water softening equipment to higher efficiency equipment can offer significant salt and water savings, reducing TDS produced from residential, commercial, and industrial water softeners. Salt efficiencies of SRWS keep improving. Newer models use less salt to soften more household water than older models. The effect of improved salt efficiency on TDS discharges is indicated in Figure 5.1. Softener Brine TDS with Varying Efficiencies (14 grain hardness) 30,000 Brine TDS from SRWS [mg/l] 25,000 20,000 15,000 10,000 5, Efficiency [grains removed/lb salt] Figure 5.1 Effect of softener efficiency on TDS of brine 85 Section 5 Potential TDS Reduction Program Components

94 In addition, the initiation basis for regeneration of the softener affects the TDS. The chart in Figure 5.2 indicates that a time clock initiated regeneration cycle will regenerate more often discharging more salts than demand initiated regeneration cycle with the same efficiency. Regeneration Frequency of DIR and Time Clock Controlled SRWS Regeneration [days] DIR Time Clock Hardness [gpg] Figure 5.2 Regeneration frequency of time clock SRWS compared with demand initiated regeneration SRWS with the same salt efficiency Equipment upgrades as a component of the salinity management program would complement a water softener efficiency and public education campaign. In addition, it could be coupled with a rebate program to encourage customers to upgrade to more efficient technologies such as demand initiated or microprocessor regeneration. Locally, Culligan of Phoenix has initiated a program called Green Solutions 3 Step Plan to inspect their customers water softening equipment to ensure its maximum efficiency. The City could encourage and/or require a more comprehensive program of equipment inspections and upgrades for residential, commercial and industrial softening as part of its overall salinity management program Pretreatment Limits The City of Phoenix Pollution Control Division manages the pretreatment program designed to control industrial discharges into the sewer system to meet local limits on the City s WWTP Arizona Pollutant Discharge Elimination System (AZPDES) and Aquifer Protection Permit (APP) permits. Revised local limits (Figure 5.3) were approved by ADEQ in December 2004 and adopted into the City Ordinances. 86 Section 5 Potential TDS Reduction Program Components

95 Figure 5.3 Local limits in mg/l (Industrial Pretreatment Report, 2006) Currently, TDS is monitored by the Pollution Control Division but there is no established limit for industrial discharges. The TDS contribution to the sewer system from commercial and industrial facilities can be significant. In 2007, wastewater flows from industrial facilities in the pretreatment program had an average of 2,136 mg/l of TDS and 6.95 MGD. Efforts to reduce the salinity loads discharged from such sites can be effective and readily enforceable. The City s AZPDES pretreatment program provides a vehicle for addressing commercial and industrial discharges of TDS to the sewer system. The City should consider the role of commercial and industrial softeners in salinity management regardless of what steps it takes with respect to regulating residential SRWS systems. Currently discharges from portable exchange regeneration facilities are not regulated Rebates The City may decide to move beyond education programs and setting standards and/or discharge limits to reduce the TDS discharged to the sewer system. The development of a rebate program would be a next logical step. The City can offer a financial incentive to users of SRWS to upgrade to higher efficiency units, convert to an alternative technology (if feasible), or remove their softener entirely. Several communities have incorporated a rebate program as part of their overall TDS management strategy (See Appendix G). The decision to offer a rebate program must consider the effectiveness of the preceding program elements along with the benefits and costs of the financial investment. A rebate program is certainly worth considering if it can bridge the gap toward meeting the water quality target without needing to move to more costly and/or controversial options. Rebate program costs should be compared to treatment costs to meet the water quality goals, and impacts to water reuse customers Bans Actions to ban the use of water softening equipment should be viewed as a last resort. It is possible that a comprehensive salinity management program that incorporates many of 87 Section 5 Potential TDS Reduction Program Components

96 the elements described above could achieve the City s goals without having to take this final step. It is also equally likely that one of the other options (TDS treatment of the source water or reclaimed water) could be more effective and/or appropriate than a ban on the use of SRWS. However, it is an option that must be considered if the City determines that it cannot achieve its reclaimed water TDS concentration targets. 5.7 Local and State Institutional Framework Information on the local and state institutional framework that was reviewed was based on internet research and limited discussions with water and softener industry representatives. Selected segments of the City of Phoenix Codes and Arizona State Laws and Regulations that could impact the regulation of SRWS and relevant comments are included as Appendix J. In general there appears to be some institutional framework for TDS control program components City of Phoenix Policies and Ordinances The following documents listed in Table 5.1 were reviewed for guidance on salinity management in the Phoenix area: Table 5.1 Phoenix Codes reviewed Phoenix Code Title Chapter 19A Residential Development Occupational Fee Chapter 19B Chapter 19C Chapter 19D Chapter 28 Commercial and Industrial Development Occupational Fee Water Residential Development Occupational Fee Water Commercial and Industrial Development Occupational Fee Sewers Chapter 30 Chapter 37 Water Resources Acquisition Fee Water Several current Phoenix City Codes were identified that could be of use in developing a salinity management program. One area within existing policies that might be worth pursuing relates to funding a potential rebate program. Under Chapters 19A, 19B, 19C, and 19D, the Use of Funds Collected sections pertaining to the various Development Occupational fees for sewer and water service could be interpreted to make such funds available to fund a SRWS rebate program. These Codes create sewer and water sub-funds to pay for capital expansions and/or refunds that further wastewater discharge reduction or water use reduction incentive plans. A program that provides a rebate to replace inefficient SRWS with more efficient units, or to remove them entirely, could be considered a program to reduce wastewater discharges and/or reduce water consumption. Ideally, funds for such programs would come from those impacting the sewershed with additional salts. 88 Section 5 Potential TDS Reduction Program Components

97 The City Codes grant authority to the Water Services Director to establish prohibitions and effluent limitations (Chapter 28; Article II; Section 28-9) and/or require Best Management Practices (Chapter 28; Article II; Section ). This portion of the Code could be evaluated as an authority to require the use of SRWS that meet minimum salt and water use efficiency standards. Taken further, this Code could also potentially be used to set discharge limitations for specific components of TDS such as sodium or chloride to address specific negative impacts. Chapter 28; Article VI covers Industrial User and Pretreatment Requirements. Under this Article, the Water Services Director has authority to enact requirements as deemed reasonably necessary to protect the quality of a receiving water among other goals (Section 28-46). Finally, under Chapter 37, the Water Services Director has responsibility for Water Conservation (Article IX) and Drought Management (Article X). These Articles could provide some framework for the City to regulate the efficiency of SRWS units as a conservation measure and/or prohibit their use as part of a comprehensive drought response plan State Laws and Regulations The following documents listed in Table 5.2 were reviewed for guidance on salinity management in the State of Arizona. The text of applicable laws and regulations is included in Appendix J. Unlike many states, Arizona state laws and regulations do not limit SRWS brine discharges to on-site septic systems. Nor does the state institutional framework specifically address SRWS discharges to municipal sewer systems or minimum efficiency standards. Arizona does not list a numeric groundwater quality standard for TDS or the specific components of TDS such as sodium or chloride. The Arizona Administrative Code does allow for the promulgation of new aquifer water quality standards if the petitioner can provide: 1) technical information that the pollutant is a toxic pollutant; 2) technical information upon which the Director of ADEQ may reasonably base a standard; and 3) evidence that the pollutant is or may in the future be present in an aquifer or part of an aquifer that is classified for drinking water protected use (R ). Interestingly, there is a significant counter-example for the regulation of TDS discharges to the aquifer. The Arizona recharge regulations exempt facilities that recharge CAP water from needing to obtain an Aquifer Protection Permit (ARS ). This exemption is in effect even where the TDS of CAP water is significantly higher than the aquifer receiving water. 89 Section 5 Potential TDS Reduction Program Components

98 ADEQ General Table 5.2 Review of State laws and regulations Program / Code Title Instructions for Uniform State of Arizona Site Investigation Report Aquifer Protection Program A.R.S AZPDES Title 18. Environmental Quality Water Quality Division (Form 222) Completeness Review Guide for Engineering Review Individual Permit Application Instructions Instructions for Transferring Ownership of a Sewage Treatment Facility Operating under a 1.09 General Aquifer Protection Permit Instructions for Submittal of a Notice of Intent to Discharge for a Type 2 General Permit NOI Supplement for a Type 2.05 General Permit (CMOM) Notice of Intent to Discharge for a Type 3 General Permit NOI Supplement for Type 3.02 General Permit for Process Water Discharges from Water Treatment Facilities Request for Discharge Authorization for a Sewage Collection System Constructed under a Type 4.01 General Permit Notice of Intent to Discharge for a Sewage Collection System Type 4.01 General Aquifer Protection Permit Request for Discharge Authorization for an On-Site Wastewater Treatment Facility Type 4.02 to 4.23 General Aquifer Protection Permits Instructions for Submittal of a Notice of Intent to Discharge for an On- Site Wastewater Treatment Facility Exemptions and Facilities to which the APP Program Does Not Apply AZPDES Application Form 1 General Information AZPDES Form 2A Application for Discharge from Wastewater Treatment Plants Treating Domestic Sewage AZPDES Form 2D AZPDES Form 2D Addendum De Minimus Discharge Program Chapter 9. Department of Environmental Quality Water Pollution Control Chapter 11. Department of Environmental Quality Water Quality Standards States are required to adopt surface water quality standards called Total Maximum Daily Loads (TMDLs) that protect impaired waterways from specific pollutants. TMDLs determine the total amount of a specific pollutant the waterway can receive and still meet the water quality standard. Examples of waterways in Arizona with site specific TDS standards include portions of the West Fork of the Little Colorado River, Cienega Creek, and Bonita Creek. TMDLs are a possible vehicle for future regulation of discharges of TDS, or specific constituents of TDS. The designation of the receiving waterway for the outfall from 91st Avenue and 23rd Avenue WWTPs is described as effluent dependent waters (R ). Water quality for this reach of the river is designated for aquatic and wildlife effluent dependent waters, partial body contact, fish consumption, agricultural irrigation and livestock 90 Section 5 Potential TDS Reduction Program Components

99 watering. However, there are currently no water quality restrictions for sodium, chloride, or TDS for effluent-dependent waters in Arizona. Arizona law gives authority to ADEQ to establish discharge limitations for point source discharges from WWTPs through the AZPDES program. The AZPDES serves to protect water quality in receiving surface waters from point and nonpoint pollution sources. The AZPDES permit allows utilities to establish local limits to control constituents of concern, including TDS. If a TDS, chloride, or sodium standard were developed, the AZPDES pretreatment program could be applied to regulate industrial and commercial SRWS brine discharges. As described previously, the Phoenix pretreatment program has not set a local limit for TDS Guidance from Other Jurisdictions As discussed in the Task 2 Technical Memorandum, several other states and local jurisdictions have some form of regulation related to the use of SRWS. Specifically, California has state-level regulations that under defined circumstances allow local entities to regulate the use of SRWS (CA Health & Safety Code ). Examples of efficiency standards for SRWS that Arizona could adopt are the WQA Gold Seal program standard of 3,350 grains of hardness per pound (grains/lb) of salt or the efficiency standard of 4,000 grains/lb included in the California Health and Safety Code (see Appendix K). The Task 2 Technical Memorandum also provided information on existing rebate programs that Phoenix could model if such a component is adopted. One example of a grant application for funds to develop a pilot rebate program is included in Appendix L. Grant money could be a vehicle for funding several aspects of Phoenix s program as it develops. Santa Clarita Valley Sanitation District in California has developed a significant public education and rebate program to deal with increasing chloride levels in the waste stream due to SRWS. The public outreach included articles in local newspapers, letters to residents, radio ads, banners, flyers for the rebate program, and a website with additional information and water softening alternatives. Examples are included in Appendix M Regulatory and Policy Gaps In general, the institutional framework in Arizona provides a broad platform upon which to regulate SRWS. In order for regulatory actions taken by the City of Phoenix to survive the political and legal challenges that would inevitably result, the City should evaluate legislative actions that should be taken to further define the framework. It is recommended that such efforts be conducted in cooperation with stakeholders such as the WQA to ensure that the needs of the City are met while maintaining broad community support. 91 Section 5 Potential TDS Reduction Program Components

100 It is likely that minimum efficiency standards for SRWS could be established at the state level. At minimum, the City should ensure that it is granted the legal authority to enforce such standards if they are established on the local level. There is currently no direct policy direction from the Phoenix Mayor and Council on salinity management. The City should seek approval from Mayor and Council to proceed with the development of a salinity management program that will evolve over time. Further, the existing City Codes provide some mechanisms for possible funding of rebate programs as well as the ability to take actions necessary to protect the integrity of the sewer system(s), treatment works, and management of the treated wastewater. 5.8 Recommendations A set of program recommendations has been developed through the course of completing Tasks 1 through 4 of this study. A preliminary list was included with the Task 2 report. These recommendations are updated in this section. The process of developing a salinity management program should be transparent and engage stakeholders early in the process. This has already begun with initial discussions with the WQA and homebuilders. Any initiative that would impact the water-softening industry in Phoenix will be a significant cause for concern to the local businesses that install softening systems. The WQA and some of its local constituents have stated a willingness to work with the City to develop a salinity management program. They have also demonstrated an aggressive track record of challenging regulatory programs that impact their interests. The City needs to make a strong case for implementing regulatory actions that are deemed necessary. The regulatory or management driver that creates the need for the program must be clearly stated. Much of the scientific information about the accumulation and impacts of salts has been assembled through the Central Arizona Salinity Study. A benefit-cost analysis should be conducted and the results made available for review and comment. All sources of TDS that can be managed should be considered. As is necessary to achieve many water quality objectives, a multi-point or multi-barrier approach is most cost effective. The regional salinity balance must be well understood before making conclusions or enacting regulatory measures. Prioritize regulatory actions that will yield the most benefit at the least cost and/or impact to local businesses. Multiple strategies should be considered as part of a comprehensive salinity management program including: o Utilize TMDLs and NPDES permit limits to regulate TDS discharges o Establish a state/regional efficiency standard for all SRWS o Maintain a consistent monitoring and sampling program to demonstrate effects of program components 92 Section 5 Potential TDS Reduction Program Components

101 o Educate homeowners on best management practices for their existing systems o Educate and/or certify operators of commercial/industrial units o Require certifications for system installers o Research new technologies and practices (e.g. off-site regeneration and alternative technologies) o Require the use of approved equipment If it is necessary to take action to reduce and/or eliminate water softening activities within the service area, the following items should be implemented: o Work with industrial, commercial and residential users of SRWS to maximize efficiencies o Take actions to prevent new systems from being installed during new construction o Require system removal upon remodel or resale o Provide incentives/rebates for homeowners to remove existing systems o Ban the use of water softeners, as a last resort Measure the results of the program on a continuous basis. Potentially phase-in more aggressive measures over time as necessary to meet the management objectives. Evaluate alternatives to regulating water softening activities in the service area. One primary alternative would be to perform point of use treatment for reclaimed water distribution and/or discharge. 93 Section 5 Potential TDS Reduction Program Components

102 6 TDS Goals for Reclaimed Water Uses 6.1 Description The City of Phoenix Water Services Department (City) is concerned about the rising concentration of total dissolved solids (TDS) and associated ions and salts in wastewater collected and received at its water reclamation facilities. TDS and its components have the potential to restrict the beneficial use of reclaimed water, increase the City s water management costs, and decrease economic and environmental sustainability of the region. The City has participated for several years in the Central Arizona Salinity Study (CASS), the Multi-State Salinity Coalition (MSSC), and numerous related initiatives and efforts to understand the sources, impacts, and implications of increasing levels of TDS in its reclaimed water. Point-of-use water treatment systems, including home and commercial water softeners, have been identified as a potentially controllable source of TDS. The City has hired HDR Engineering to conduct the study described herein to gather information necessary for the City to make a decision regarding the implementation of policy to control TDS discharges associated with point-of-use water softening and other treatment systems. As part of the Citywide Water Softener Study, the City asked HDR to research maximum tolerance concentration levels of TDS that have been recommended by previous studies for reclaimed water uses such as groundwater recharge, golf course irrigation, turf irrigation for public areas and industrial/commercial cooling systems. Elevated TDS concentrations and its component concentrations in water can have a negative affect on vegetation, soils and scaling of cooling tower materials. TDS is commonly referred to as salinity and is approximated by the amount of inorganic salts (calcium, magnesium, sodium, potassium, chloride, sulfates and bicarbonates) and organic solutes. Certain constituents of TDS such as sodium and chloride can significantly damage plants and soils. 6.2 Reclaimed Water Quality In Arizona, there are five classes of reclaimed water: Class A+, Class A, Class B+, Class B, and Class C. The classifications are based upon a combination of minimum treatment requirements and water quality criteria. The water quality criteria do not include considerations for TDS, and are focused on pathogenic microbes. Minimum Treatment Requirements: Class A: wastewater that has undergone secondary treatment, filtration, and disinfection. Class B: wastewater that has undergone secondary treatment and disinfection. Class C: wastewater that has undergone secondary treatment in a series of wastewater stabilization ponds, including aeration, with or without disinfection. The total retention time of Class C reclaimed water in wastewater stabilization ponds must be at least 20 days. 94 Section 6 TDS Goals for Reclaimed Water Uses

103 The + designation for either Class A or B water requires that the designated water has been treated such that the total nitrogen concentration is less than 10 mg/l. The + designation is typically necessary when reclaimed water has the potential to interact with groundwater beneath where the water is being applied. Class A reclaimed water is required for applications where there is a high likelihood that humans will be exposed to the water. Where the potential for human exposure is lower, use of Class B and C water is acceptable. Phoenix does not produce any Class C reclaimed water for reuse. The approved uses for Class A water in Arizona are as follows: Irrigation of food crops Recreational impoundments Residential irrigation School ground irrigation Open access irrigation Toilet and urinal flushing Fire protection systems Spray irrigation of orchards/vineyards Commercial closed loop air conditioning Vehicle/equipment washing Snowmaking The approved uses for Class B water in Arizona are as follows: Surface irrigation of orchards/vineyards Golf course irrigation Restricted access irrigation Landscape impoundment Dust control Soil compaction Pasture for milking animals Livestock watering Concrete / cement mixing Materials washing Street cleaning 6.3 Existing TDS Goals Salts are concentrated as water is treated, distributed, disposed and the wastewater is collected and reclaimed at a wastewater treatment plant (WWTP) to meet water quality requirements of the water s next use. In general, there is a mg/l TDS increase from Phoenix source waters to the WWTPs. To manage the salts, TDS goals may be applied at the water treatment plant, discharge locations into the sanitary sewer, and at discharge locations from the WWTP. 95 Section 6 TDS Goals for Reclaimed Water Uses

104 There are no regulated standards or criteria for TDS in reclaimed water for allowable applications. However, there are a limited number of TDS goals and recommendations that are appropriate for consideration in the Phoenix area. USEPA s secondary Maximum Contaminant Limit (MCL) for TDS in drinking water is 500 mg/l. The secondary standards are not enforceable but do represent a level where aesthetics affect the drinkability of water. Most surface water and groundwater sources that supply Phoenix drinking water are higher than 500 mg/l in TDS. The City s Pollution Control Division manages a pretreatment program under the Clean Water Act and the National Pollutant Discharge Elimination System (NPDES). The pretreatment program regulates the water quality in discharges from industries in the Phoenix sewersheds to protect the WWTPs, wastewater collection and treatment operators, and quality of effluent discharges into waterways. The TDS from industrial discharges has been monitored in this program but a goal has not been established. TDS concentrations range from 70 to 44,000 mg/l in discharges from permitted facilities (COP, 10/14/08) to the City s sewage collection system. The Sub-Regional Operation Group (SROG) made up of the cities of Phoenix, Scottsdale, Glendale, Mesa, and Tempe has recommended a goal of 1,200 mg/l TDS for effluent of the 91st Avenue WWTP (CASS Phase I, 2003). Reclaimed water uses can be negatively impacted by elevated TDS levels and / or constituents of TDS such as sodium and chloride. Recently, the City of Scottsdale agreed to deliver reclaimed water with sodium and chloride concentrations less than 125 mg/l and 70 mg/l, respectively, during four months out of the year (Clark, 11/3/08). A study which developed the water quality parameters also suggested a reclaimed water TDS goal of 450 mg/l or 600 mg/l, depending upon whatever is the current CAP water quality (DSWA, 2006). 6.4 Phoenix Area Reclaimed Water Uses Reusing water represents good stewardship of a limited resource. Use of reclaimed water can offset competing demands between municipalities, agriculture, thermoelectric generation and the environment and provide operational flexibility. There are many applications for reclaimed water in communities including agriculture irrigation, landscape irrigation, industrial/commercial cooling, fire demand, environmental and recreational uses, groundwater recharge and surface water augmentation. Not all uses require drinking water quality; however, the acceptability of reclaimed water is dependent on the physical, chemical and microbiological content of the water. In Phoenix, the majority of wastewater treated is reused in cooling towers for power generation, agricultural irrigation, habitat restoration, groundwater recharge, and golf course and landscape irrigation. Of the 187 MGD treated wastewater in 2007 for the City of Phoenix, 26 percent went to Palo Verde Nuclear Generating Station (PVNGS) for use in cooling towers, 34 percent went to agriculture, 12 percent was used for riparian habitat restoration, 1 percent was used for turf irrigation, 1 percent was recharged to 96 Section 6 TDS Goals for Reclaimed Water Uses

105 groundwater, and 26 percent was released into the Salt River (much of which is used by downstream users for agricultural irrigation. Refer to Figure 6.1 for a graphical depiction of the fate of the City s reclaimed water in Agriculture 34% Palo Verde 26% Env 12% Turf 1% Recharge 1% Salt River 26% Figure 6.1 Fate of treated wastewater in Phoenix in 2007 Phoenix has agreements with Buckeye Irrigation District to deliver up to 35.7 MGD of treated wastewater from 91st Avenue WWTP for irrigating crops such as cotton. Nearly 25 MGD of treated wastewater is committed to the Tres Rios Habitat Restoration Project by 2010 (Fluid Solutions, 2004). The Tres Rios is a managed wetland which provides additional water quality polishing and provides for riparian habitat and wildlife and provision of educational and recreational resources. Phoenix and the other SROG cities have an agreement with the operator of the PVNGS to deliver up to 90,000 AFY (equivalent to a daily average of 80.3 MGD). Finally, 47.4 MGD was discharged from 91st Avenue WWTP through the NPDES permit into the Salt River. Some of the water delivered to the River is subsequently diverted and used for agriculture. The 23rd Avenue WWTP produces B+ quality reclaimed water used for irrigating melons and vegetables in the west valley (Western Resource Advocates, 2003). Approximately 26.8 MGD of wastewater from 23rd Avenue WWTP is transferred to Roosevelt Irrigation District (RID). In some years, deliveries in excess of 26.8 MGD (30,000 AFY) results in the accumulation of long-term groundwater storage credits for Phoenix. Phoenix operates the Cave Creek Water Reclamation plant (CCWRP) to treat wastewater and deliver it for turf irrigation. The CCWRP is currently receiving an average 4.4 MGD. Reclaimed water customers for the CCWRP water include 3 golf courses, 6 parks and recreational facilities and one cemetery for a total annual delivery of million gallons or 1.7 MGD (Terrey, 10/31/08). The remaining reclaimed water is injected into the vadose zone for groundwater recharge. 97 Section 6 TDS Goals for Reclaimed Water Uses

106 6.5 Maximum TDS Tolerances Water quality considerations for irrigation customers include those that affect soil properties and those that affect the growth of the plant. For aquifer recharge, water quality concerns are associated with those that affect soil drainage, and constituents of concern that may percolate to the water table. Additionally, higher TDS source water for recharge can mix with native groundwater to produce a mixed groundwater quality with TDS concentrations that are noticeable by water users. For the industrial cooling customer, compatibility of the water chemistry with the cooling tower materials is critical for operation and maintenance. Chlorides can corrode stainless steel and ammonia can cause stress corrosion cracking in copper alloy. High TDS in cooling water results in lower cycles of concentration, thereby increasing costs. The TDS goal for reclaimed water uses should be determined by evaluating the tolerance to TDS and / or the impact due to specific constituents of TDS for each use. Goals may be established for each WWTP based on the majority of demand for reclaimed water but should also consider opportunities for increased future use of reclaimed water for other uses. Some agencies, such as the West Basin Municipal Water District in California, have designed and constructed separate treatment trains to produce up to six qualities of water (based in part on TDS requirements) for their reclaimed water customers Agriculture In Arizona, approximately 34 percent of treated wastewater is used by agriculture. Much of this reclaimed water is used in exchange for groundwater that would otherwise have been pumped to meet agriculture demands, and that can now be used for other purposes, such as drinking (whereas reclaimed water cannot). Groundwater basins benefit from reduced groundwater pumping; however increasing soil salinity can become an issue MGD from 91st Avenue WWTP is used for irrigating crops like cotton through the Buckeye Irrigation District. Another 26.8 MGD from the 23rd Avenue WWTP is delivered through the RID for crops such as melons and vegetables. The RID groundwater savings facility is used to replace up to 30,000 AF of groundwater pumping for agricultural use with treated wastewater. Water treated at 23rd Avenue WWTP is delivered to RID canals for delivery to West valley agricultural users. Arizona requirements for reclaimed water applied to food and nonfood crops are presented in Table 6.1 Table 6.1 Arizona reclaimed water quality requirements for crops (Metcalf & Eddy, 2007) ARIZONA Food Crops Non Food Treatment secondary treatment, filtration and disinfection secondary treatment, filtration and disinfection BOD NS NS TSS NS NS Turbidity 2 NTU (avg) NS Fecal Coliform non detectable < 200/100 ml NS Not Specified Water quality considerations for irrigation customers include those that affect soil properties and those that affect the growth of the plant. Dissolved salts in soil have an 98 Section 6 TDS Goals for Reclaimed Water Uses

107 osmotic affect as water migrates from areas of low salt concentrations near the root zone to higher salt concentrations in the soils, which will stress plants and cause wilting. TDS in irrigation water can cause desiccation (burn) of foliage and fruits. Crop damage is related to sensitivity of the plant which changes at each growth stage. Plants are most sensitive to water quality during germination and early growth periods. As irrigation efficiency increases, salts will increase in the soils and will require occasionally leaching to flush the salts from the root zone. Lime deposition is another characteristic of high TDS water and can cause clogging of sprinkler heads, and reduce marketability of fruits and vegetables. High lime concentrations in soils can also reduce the effect of certain fertilizers. The recommended limit for TDS in reclaimed water for irrigation is mg/l, depending upon the irrigated vegetation (see Table 6.2). Below 480 mg/l, no detrimental effects are usually noticed. Between 480 and 1,280 mg/l, TDS in irrigation water can affect sensitive plants. At 1,280 to 1,920 mg/l, TDS levels can affect many crops and careful management practices should be followed. Above 1,920 mg/l, water can be used regularly only for tolerant plants on permeable soils (PNW, 2007). Table 6.2 Salinity hazard from irrigation water (PNW, 2007) Water electrical conductivity (EC) Water total dissolved solids (TDS) Salinity hazard and effects on management (mmhos/cm or ds/m) (ppm) Below 0.25 Below 160 Very low hazard. No detrimental effects on plants, and no soil buildup expected Low hazard. Sensitive plants may show stress; moderate leaching prevents salt accumulation in soil ,280 Medium hazard. Salinity may adversely affect plants. Requires selection of salt-tolerant plants, careful irrigation, good drainage and leaching ,280-1,920 Medium-high hazard. Will require careful management to raise most crops. Above 3.0 Above 1,920 High hazard. Generally unacceptable for irrigation, except for very salttolerant plants where there is excellent drainage, frequent leaching and intensive management. Specific ions in reclaimed water including sodium, chloride and boron can be toxic to plants (MetCalf & Eddy, 2007). Boron is beneficial nutrient for soils but greater than 0.5 mg/l can be toxic to sensitive plants. If chlorides are too concentrated it can turn leaves yellow and stunt growth. Table 6.3 indicates chloride tolerances of specific crops. 99 Section 6 TDS Goals for Reclaimed Water Uses

108 Table 6.3 Chloride tolerances for crops (PNW, 2007) Chloride Effect on crops Susceptible plants (mg/l or ppm) Below 70 Safe for most plants Rhododendron, azalea, blueberry, dry beans Sensitive plants show Onion, mint, carrot, lettuce, pepper, grape, raspberry injury Moderately sensitive Potato, alfalfa, sudangrass, squash, wheat, sorghum, corn, tomato plants show injury Above 350 Can cause severe problems Sugarbeet, barley, asparagus, cauliflower The maximum tolerance for agriculture will depend on the crops being grown, and the soil type. Cotton a saline tolerant crop has a EC threshold of 7.7 ds/m (~ 6,160 mg/l TDS) Issues with Sodium Elevated concentrations of sodium ions limit water movement in soils and create a plant growth hazard which is measured by the Sodium Adsorption Ratio (SAR). SAR is the proportion of sodium (Na) ions compared to the concentration of calcium (Ca) plus magnesium (Mg). + Na SAR = Ca + Mg 2 When the SAR rises above certain levels, serious soil problems occur and plants have difficulty absorbing water. Depending on the type and content of the clay, adverse affects on soil structure are observed when SAR is above 5. For other soils, a SAR greater than 15 will cause soils to become hard reducing infiltration due to the excess of sodium. To reduce the SAR ratio, gypsum is often applied to soils. Gypsum frees the sodium in the soils so it can be leached. Carbonate and bicarbonates in irrigation water can also have an affect on sodium levels in the soils. These ions cause the Ca and Mg ions to precipitate out of water resulting in a higher sodicity. Irrigation with water that has been softened by ion exchange, which exchanges sodium ions for calcium and magnesium ions, increases the SAR and accelerates the degradation of the soil. The interaction between the SAR of the soils and the TDS of the irrigation water is indicated in Figure Section 6 TDS Goals for Reclaimed Water Uses

109 Figure 6.2 Combined effects of SAR and EC on soil infiltration rate (AwwaRF, 2006) Reclaimed irrigation water generally has higher salinity than potable water and unless adequate leaching fractions are used, salts will accumulate in the root zone of plants. Potential problems of using irrigation water with higher salinity are a deterioration of soil quality, including increasing soil salinity, accumulation of specific ions, increasing sodicity, and decreasing soil permeability and water infiltration. (UA, 2008) Industrial and Commercial Cooling As mentioned previously, Phoenix sells 26 percent of its wastewater to the PVNGS for use in cooling towers. In 2007, 47.7 MGD were delivered to the PVNGS (Day, 2007) for use in cooling towers. The PVNGW lime softens the water as it comes into the plant to prevent scaling and corrosion in the cooling towers. In addition to the PVNGS, many industrial and commercial facilities conduct cooling on a large scale and could be utilizing reclaimed water. The City of Phoenix conducted a study in 2003 characterizing industrial and commercial cooling which indicated that industrial locations may use up to 60 percent of their water for cooling (TNT, 2003). Cooling is generally accomplished using an evaporative process which consists of a cooling tower and a heat exchanger. Cooling towers use ambient air to cool water that has been warmed through some process. Water is evaporated in the tower which cools a recirculating stream of water. As the heat is taken away by the air, approximately 1 percent of the water evaporates for every 10 F of cooling. The cooled water cycles back to the heating processes to take on more heat passed through a heat exchanger and is returned to the tower for cooling again. As the water evaporates the salts are concentrated in the remaining water which can affect scaling, corrosion and solids buildup in the cooling infrastructure. Water is bled from the system after a number of cooling cycles to control salinity in the recirculating water. Cycles of concentration refers to the number of times water can be used in the tower prior to blowdown or discharge into the sewer system. Water chemistry of cooling water is critical to manage operational and maintenance costs. Reclaimed water with too much ammonia, chlorides, phosphates, sulfate and TDS 101 Section 6 TDS Goals for Reclaimed Water Uses

110 can lead to microbiological growth, corrosion and reduced cycles of concentration. Cooling towers are ideal incubators for microbiological growth due to the warm temperatures, the concentration of nutrients in make up water for microorganisms, and the quick decay rate of disinfection residual due to air stripping. Ammonia acts as a nutrient for microbiological growth which can lead to fouling and corrosion cracking of copper alloys. Certain systems can not tolerate more than 0.2 mg/l of ammonia (AwwaRF, 2006). Chlorides and sulfates accelerate corrosion in carbon steel, galvanized steel and low grade stainless steels. The Larson-Skold index is a ratio of equivalents per million (epm) of chloride and sulfate to that of bicarbonate and carbonate. This index is used to determine the impact of the water on corrosion of steel in the cooling systems. A Larson-Skold index greater than 0.8 indicates corrosion potential. The TDS in the water affects the number of cycles that the water can be used prior to blowdown. Often operators use chemical or mechanical processes to reduce feed water hardness to limit scaling and increase the cycles of concentration, thereby reducing the water demand for the facility. Generally, the upper specification limit for TDS in cooling system feed water is 2,500 to 3,000 mg/l (AwwaRF, 2006). ADWR, through the Third Management Plan and likely through future management plans, regulates the number of cycles of concentration of water for cooling systems in large scale power plants (greater than 25 MW) and other large scale cooling systems. The regulations are truncated and summarized as follows: Large Power Plants Power plants producing more than 25 MG of power that were in operations as of the end of 1984 must achieve an annual average of 7 cycles of concentration in cooling towers. Facilities that went into operation after 1984 are required to achieve an annual average of 15 cycles of concentration in their cooling towers. The cycles of concentration requirement applies only during periods when facilities are generating electricity and applies only to fully operational towers that are dissipating heat from the power generation process. Facilities may be granted adjustments to their full cycles of concentration requirements in cases (including based upon source water quality) where adhering to the standard is likely to result in equipment damage or blowdown water exceeding environmental discharge standards. Large Scale Cooling Facilities Large scale cooling facilities are facilities with a total aggregate cooling capacity of 1,000 tons or more. The following conservation requirements apply to individual cooling towers within large scale cooling facilities that have 250 tons of cooling capacity or more: Must achieve either 120 mg/l of silica or 1,200 mg/l of total hardness in recirculating water, whichever is reached first, before blowing down. 102 Section 6 TDS Goals for Reclaimed Water Uses

111 If needed, a facility may apply for an alternative blowdown standard for any tower o using effluent, or o if compliance with blowdown requirements would likely result in damage or exceedance of environmental discharge standards. The PVNGS s three units came on line after 1984, and typically blows down water from its cooling towers when the concentration reaches approximately 25,000 mg/l TDS, which is between 4 and 5 cycles of concentration assuming an initial source water TDS of 1200 mg/l TDS NPDES Permitted Discharges States are required to adopt surface water quality standards called Total Maximum Daily Loads (TMDLs) that protect impaired waterways from specific pollutants. TMDLs determine the total amount of a specific pollutant the waterway can receive and still meet the water quality standard. Examples of waterways in Arizona with site specific TDS standards include portions of the West Fork of the Little Colorado River, Cienega Creek, and Bonita Creek. The designation of the receiving waterway for the outfall from 91st Avenue and 23rd Avenue WWTPs is described as effluent dependent waters (R ). Water quality for this reach of the river is designated for aquatic and wildlife effluent dependent waters, partial body contact, fish consumption, agricultural irrigation and livestock watering. While there are no surface water quality restrictions specifically for sodium, chloride or TDS for this reach of the river, high chloride concentrations can limit the ability to discharge, as discussed below. Effluent discharged from a WWTP pursuant to a NPDES (or AZPDES, in Arizona s case) permit is required to pass the whole effluent toxicity (WET) test. The test measures the toxic effect of the effluent to aquatic organisms to grow and reproduce. A number of aquatic species are used for the test including the Ceriodaphnia dubia, a water flea species. High chloride concentrations (approximately 300 mg/l) in the effluent are known to cause failure of this test. In cases like Tres Rios, the WET test can be used to determine the max level of pollutants which would have an impact on an aquatic plant species or the macro-organism community. TDS concentrations increase from 1,055 mg/l at the 91st Avenue outfall to 3,800 mg/l at the Arlington Canal near Buckeye (Poulson, 2008) Environment Treated effluent from the 91st Avenue WWTP, owned by the SROG, has been recharged over many years into the Tres Rios Area, a 500-acre system of constructed wetlands, to polish the effluent for water quality improvements and to enhance the quality and quantity of riparian habitat along the Salt River. 103 Section 6 TDS Goals for Reclaimed Water Uses

112 The Tres Rios Habitat Restoration Project has been in operation since The project operated by the Army Corps of Engineers and the SROG has been successful at meeting water quality standards required under the NPDES permit. There is no TDS goal for the Tres Rios project; however, TDS could have an impact on the riparian area if it increased to the level where it began to affect either the vegetation or some of the aquatic species. Many of the native aquatic species such as the pupfish and top minnow and native vegetation in the Tres Rios have high salt tolerances. Salinity impacts to some of the vegetation would limit the effectiveness of the water quality improvements of the managed wetland, and affect the habitat required for some of the protected fowl and aquatic species Groundwater Recharge In Arizona, the practice of recharging aquifers with reclaimed water is regulated through the Aquifer Protection Permit (APP). The APP describes the water quality standard that the water must meet prior to being applied for surface recharge or through injection wells. Depending on the location and proximity to nearby wells, water recharged through injection wells, may be required to meet drinking water standards. Recharge facilities in Arizona are required to obtain Recharge Permit from the Arizona Department of Water Resources (ADWR). Cave Creek Water Reclamation Plant Recharge Facility recharges excess water that is not delivered to reclaim customers. A maximum of 8,961 acre-feet of effluent per year is recharged via seven vadose zone wells. CCWRP produces A+ quality reclaimed water with an average TDS of 1,121 mg/l. The City may at some point pursue the option to recharge the regional aquifer with reclaimed water through the Agua Fria Linear Recharge Project. The SROG, teamed with the Bureau of Reclamation, has conducted environmental and feasibility studies to identify opportunities to recharge the aquifer underneath the Agua Fria River (Agua Fria Linear Recharge Project). The purpose of the current phase of the project is to investigate the possibility of using high quality reclaimed water from the 91st Avenue WWTP to replenish the aquifer (Figure 6.3). 104 Section 6 TDS Goals for Reclaimed Water Uses

113 Figure 6.3 WWTP and recharge facilities for Phoenix wastewater (Phoenix, 2008) There is currently no reclaimed water quality standard for recharge application in Arizona. Reclaimed water is likely to have higher TDS concentrations than native groundwater. If groundwater recharge with reclaimed water were to cause the TDS concentration in the regional groundwater to increase to point noticeable by the water using public, the public may become concerned about the source of recharged water or may pressure the City to treat the reclaimed water or the recovered groundwater to reduce the TDS concentration. TDS may have implications on the rate of infiltration due to the SAR ratio if the recharge is applied through a spreading basin. Recharge through spreading basins allows water to percolate through the soil layers as an additional treatment prior to reaching the water table. For groundwater recharge of domestic water supply aquifers by surface spreading, the reclaimed wastewater must be at all times of a quality that protects public health Turf Irrigation The Cave Creek Reclamation Plant delivered million gallons between July 2007 to June 2008 for reclaimed water customers. The City currently manages 10 contracts with parks, recreational areas, cemeteries and golf courses for turf and landscape irrigation. The largest users of the CCWRP reclaimed water are three golf courses which utilize 84.5 percent of the water. With increasing TDS from the CCWRP, some customers are seeing impacts to golf turf. Golf courses use a combination of warm season grasses such as bermuda and pas pallum and cold season grasses such as bentgrass, fescues and ryegrass for varying locations throughout the course. The TDS tolerances of these grasses vary and are represented in Table 6.4 Water requirements for golf turf are higher than other landscaping plants due 105 Section 6 TDS Goals for Reclaimed Water Uses