An Operational Definition of Biostability for Drinking Water Project #4312. Case Studies

Transcription

1 METHODS An Operational Definition of Biostability for Drinking Water Project #4312 Case Studies Utility Case Studies and Current Biostability Practices The purpose of the case studies was to collect information from the 26 participating facilities to characterize their source water, treatment processes, and distribution system; benchmark current practices for monitoring and control of biostability in distribution systems; compile historical case-studies of issues with biological instability and mitigation practices; and statistically evaluate historical data to identify associations between biostability, water quality, and distribution system characteristics. For each facility, a survey, historical data review, sampling and analysis, were conducted. The sampling and analysis program involved collection of a single sample from the finished water that was analyzed for assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). Both AOC and BDOC have been identified in numerous research studies as key factors associated with biostability (Camper et al. 2000, Volk and LeChevallier 2000). However, none of the participating utilities regularly monitored for AOC or BDOC in the finished water or distribution system. The historical data in conjunction with the water quality, treatment process, and distribution system characteristics were used for the screening and selection of utilities for participation in the full-scale sampling and analysis program. Survey and Historical Data The case study data collection effort incorporated information on treatment system designs; biostability treatment goals and objectives; and biostability management programs. A data request was submitted to each utility (Appendix A1) along with a template for compiling the information (Appendix A2). Specific data requested included: a system process flow diagram; distribution system map; sampling and analysis schedule and program; This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

2 one year s historical data on including monitoring and control data from online instruments and results from sampling and analysis for raw, finished water, and in the distribution system; one year s historical data on operations and maintenance activities; hydraulic model information including water age to monitoring points; recent special studies conducted on or relating to biological stability; and other feedback on overall design, monitoring, operations, control, and performance in achieving biological stability. Each utility was interviewed to communicate the objectives of the project and collect detailed information on management practices and current or historical problems with biostability. Information obtained from the survey was used in conjunction with one year of historical data to identify water quality problems. The historical data included monitoring data such as source, finished, and distribution system water quality; treatment plant doses of preoxidants (i.e. ozone, chlorine, permanganate), disinfectants (i.e. chlorine or chloramines), corrosion inhibitors (i.e., zinc phosphate, orthophosphate), and flow; distribution system characteristics such as pipe materials, pipe age, and hydraulic residence time; system management practices such as the type and frequency of monitoring; and maintenance parameters such as system flushing and pipe replacement. These data were obtained from online data sources [e.g., supervisory control and data acquisition (SCADA) data], analytical results from regularly scheduled sampling and analysis, operator s logs, and from the facility s standard protocol for maintenance and management of their distribution system. Other operational data were also compiled including sediment accumulation, frequency and duration of flushing, pipe lining, and main replacement and repair. The case-studies and historical data were compiled into a database by utility (Appendix B). Identification of Water Stability Problems Identification of systems with and without stable water is necessary to determine what factors are key drivers and in turn develop an operational definition of biological stability. During the survey, the utilities provided feedback on the types of water stability issues they have experienced, possible causes, and the mitigation strategies used. The historical data was reviewed and screened based on preliminary criteria (Table 1). These criteria were selected from various water quality standards. However, the intention of these preliminary screening criteria was to provide an initial framework for comparison between the utilities. These screening criteria were not intended to be used as the operational definition of biostability, but merely were used as an interim comparison to gain insight on what types of issues were present. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

3 Table 1 Historical issues with biostability based on evaluation of data provided for Historical Stability Problems Metric Elevated HPCs/Coliforms HPC > 100 CFU/mL, total coliforms > 0 (4) Nitrification Nitrate/nitrite formation Elevated DBPs THMs 40 ug/l and HAA 30 ug/l (4) Low Chlorine Residual <0.5 mg/l free chlorine, < 1 mg/l total chlorine for chloramines (1) High finished water AOC >100 ug acetate-c/l (1) High finished water BDOC >0.4 mg/l (2) Turbidity > 1 NTU Color > 3 CU (5) Odor odor occurrences Saturation Index Negative (3) High ph >8 (3) Low ph <6.5 (3) Low Alkalinity < 75 mg/l Low Chlorine : Ammonia Ratio <3:1 (3) References 1. Camper et al Clement et al Fiske, Oppenheimer, and Heimel EPA Stage 1 and Stage 2 DBP rule MCLs (annual average), or SDWA MCLs. 5. AWWA Water Quality Goals. Statistical Evaluation Finally, the data were statistically evaluated to identify associations amongst various parameters. The analysis was conducted on data from 16 of the 26 utilities. The 16 were selected to include the systems with known historical and/or current problems with biostability, as well as those without stability problems. The utilities included were intended to represent the range of characteristics that the 26 utilities encompassed. MiniTAB15 statistical software was used to identify relationships between potential causes and effects. The effects where focused on water quality changes relating to biostability, for example changes in disinfectant residual, heterotrophic plate count (HPC) and coliform bacteria, disinfection byproducts, ammonia, nitrate, and nitrite within the distribution system. Potential causes included finished water quality (e.g., temperature, organic carbon concentration, disinfectant residual, etc.), distribution system characteristics (e.g., pipe age and material of construction, hydraulic residence time, etc.), and control parameters (e.g., disinfectant dose, corrosion inhibitor dose, etc.). The data were statistically evaluated by sorting the potential cause into groups based on categories for discrete data or high and low values for continuous data. An example of discrete data would be the pipe material of construction, such as ductile iron. An example of continuous data would be chlorine dose. Continuous data were sorted by high and low values based in the average of the year s historical data set for that parameter. Temperature was the only case where a single value (i.e., 15 degrees Celsius) was consistently used as the metric for grouping the data. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

4 It is well documented that temperatures greater than 15 degrees Celsius have a significant impact on bacterial regrowth (Camper et al. 2000). Box plots showing the ranges in high and low values were plotted against factors most likely to be a cause of water stability or instability. For example, the box plot could contain temperature categorized as above or below 15 degrees Celsius on the x-axis and quantitative HPC data on the y-axis. The graphs were visually inspected to determine whether the y-axis data were different for the two categories on the x- axis. Comparisons were made for quartile data and outlier data. Outliers were noted because some parameters, such as coliform counts, were typically very low but incidences of increased concentrations were of interest. A matrix of causes and effects was compiled indicating the type of offset observed. The associations between potential causes and effects observed in the historical data are one of the first major steps towards development of an operational definition of biological stability. The effects observed were grouped into the following stability related problems or effects: bacterial regrowth nitrification increased disinfection byproducts, and low disinfectant residual. Bacterial regrowth included changes in concentrations of organisms such as HPCs, total coliforms, fecal coliforms, and nitrifying bacteria. Nitrification included decreases in ammonia concentrations, increases in nitrite or nitrate concentrations. Increased disinfection byproducts included formation of trihalomethanes and haloacetic acids. Low disinfectant residual was identified by free or total chlorine. The box plots were used as a tool to screen whether the cause (for example high or low temperature) influenced the effect data (for example HPCs). This method was used as a preliminary screening tool to identify associations between potential causes of instability and effects. Multiple variables influence water stability and the historical data reviewed was limited by the frequency and completeness of data reported. Therefore the results of this analysis should be viewed as an initial framework and will be refined in later stages of the project. AOC and BDOC Sampling and Analysis A sample representing a single snapshot of finished water quality was collected at each of the utilities during March and April Some of the utilities participated in Foundation project 4213, Assessing and Enhancing Biological Filtration. During that project, samples were collected during the spring of 2011 and analyzed at American Water s research laboratory (located at the Delaware River Regional Water Treatment Plant in Delran, NJ) for AOC and BDOC, in addition to a suite of other analytes. The team used the results from that sampling program so as to not duplicate efforts between the two projects. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

5 Selection of Sites and Options for Full-Scale Monitoring The robust dataset of utility information compiled during Phase 2 was used to select utilities that would participate in Phase 4, the full-scale sampling and analysis program. A matrix of characteristics for each utility was created to allow comparisons and analysis of factors that influence stability. The matrix included the raw water source, treatment process, temperature ranges, disinfectant residual type and levels, AOC and BDOC levels, corrosion control types and levels, pipe materials, residence time and hydraulic effects, nutrient concentrations, and maintenance programs. None of the participating utilities had recent AOC or BDOC data for finished water. Samples were analyzed at American Water s research laboratory. This was conducted to have comparable results and enable selection of utilities with a range of organic carbon fractions in water entering the distribution system. The historical data provided by each of the utilities was reviewed to select systems that would best represent the universe of factors potentially affecting biological stability. The following factors were used in the utility selection: source water, treatment process, temperature, disinfectant residual and disinfectant level, AOC and BDOC levels, corrosion control and pipe materials, hydraulic residence time, nutrient concentrations, and operational considerations including accumulation of sediments, the frequency and type of flushing, the rate of cleaning, relining and main replacement, distribution system maintenance and main repair; among others. The Phase 3 selection process included review of the 20 utilities that agreed to participate in Phase 4. The utilities were initially screened for those that had information on the hydraulic residence time of their system and responsiveness. The utilities were then screened by reviewing the historical data to capture a representative range of water quality and distribution system characteristics. Other factors such as the presence or absence of stability problems were used as a part of the selection process. During the Project Advisory Committee (PAC) meeting, the decision matrix was reviewed to determine which 6 facilities would participate in Phase 4. RESULTS Utility Case Studies and Current Biostability Practices Two levels of data collection were obtained during Phase 2. The first level included benchmarking utility characteristics, current methods for monitoring and control of biological stability, and current or historical problems with biostability. The second level included screening of facilities with and without stability problems, and a more detailed statistical analysis of historical data. Survey and Historical Data The participating utilities represented a broad range of source water quality, treatment processes, and monitoring and control parameters for managing biological stability in the distribution system. Table 2 lists the characteristics of the 26 facilities, which encompassed 19 distribution systems (7 utilities had two facilities that fed into different locations in the same distribution system). The systems used predominately surface water - 58 percent were from lakes This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

6 or reservoirs, 22 percent were from rivers, and 8 percent were a combination of lake/reservoir and river water. Eight percent of the systems used groundwater supply and 4 percent were mixed (surface and groundwater) systems. The 26 systems represented a variety of filtration processes (biological, GAC, anthracite, sand) and spanned the spectrum from ultrafiltration membrane filters to unfiltered water systems. Preoxidation methods included ozone, chlorine and permanganate, and post-disinfection included UV, free chlorine, and chloramine. There were three systems that added chlorine to the distribution system at booster stations to maintain a disinfectant residual in the distribution system. Seventy-three percent of the systems used free chlorine and 27 percent used chloramine. Methods for corrosion control ranged from none to ph adjustors (some operating at elevated ph) to alkalinity stabilizers to orthophosphate and blended polyphosphates. The distribution systems were varied in size, detention times, age, materials, operational practices, and monitoring programs (Tables 2 and 3). For example, the longest system hydraulic residence time was less than 3 days for 19% of the facilities, 25% were between 3 and 6 days, 44% were between 6 and 9 days, and 13% were greater than 9 days. The system ages ranged from newer systems, with the oldest pipes less than 50 years old to systems with pipe ages as high as 140 years old. Pipe materials of construction were most commonly cast iron, ductile iron, and polyvinyl chloride (PVC). Of the facilities surveyed, 69 percent used cast iron, 69 percent used ductile iron, and 50 percent used PVC. These materials were also most commonly the largest percentage of pipe in terms of miles (Table 3). This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

7 Table 2 Facility and distribution system characteristics. Source Water Treatment Process Finished Water Distribution System Pipe Material Maintenance Monitoring Facility ID 1-CA River Reservoir Lake Groundwater Ozone Other Pre-oxidant No Filtration Filtration Biological Filtration Membrane Filtration UV Conventional Free Chlorine Chloramine Corrosion inhibitor ph Adjustment Alkalinity Stabilizer Steel Ductile Steel Concrete 2-CA Cement-Lining Transite Cement 3-WI 4-WI 5-CO 6-CO 7-OK 8-OK 9-GA 10-GA 11-MI 12-MI 13-VA 14-OH 15-OH 16-MA 17-MN 18-MN 19-AZ 20-NJ 21-NJ 22-NC 1 23-MA 24-TX 25-TX 26-NY Cast Iron Ductile Iron Galvanized Iron Copper Brass Polyethylene PVC PCCP Flushing Program Increase Flow Lined Pipe Replace Pipe Clean Storage Tank None Disinfectant DBPs Coliforms HPCs Temperature Ammonia Nitrate/Nitrite TDS Turbidity None This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

8 Facility ID Finished Water Table 3 Finished water and distribution system characteristics. Distribution System Characteristics Residence time (days) Disinfectant Stabilizer Materials Disinfectant Stabilizer Pipe Age (yrs) Min Avg Max 1-CA chlorine caustic soda steel, PCCP none added none added CA chloramine caustic soda steel none added none added WI 4-WI chloramine phosphoric acid cast iron (65%), ductile iron (32%) none added none added CO chlorine lime, carbonic acid 6-CO chlorine sodium hydroxide cement-lined cast/ ductile iron (66%), PVC (22%) none added none added OK chlorine sodium hydroxide cast iron (46%), ductile iron (23%), PVC (17%), reinforced 8-OK chlorine sodium hydroxide concrete (5%) none added none added GA chlorine lime, blended 10-GA chlorine ortho/polyphosphate ductile iron (51%), PVC (33%), asbestos cement (7%), cast iron (4%) none added none added MI chlorine phosphoric acid PCCP (88%), cement-lined ductile iron (8%), PVC (4%) chlorine none added < MI chloramine sodium hydroxide cast iron (50%), cement-lined ductile iron (48%) none added none added < VA chlorine orthophosphate, caustic 14-OH chlorine sodium hydroxide 15-OH chlorine none ductile iron (35%), PVC (32%), cast iron and cement-lined cast iron (10%), unknown/other (18%) none added none added ductile iron (34%), gray iron (59%), concrete (5%) chorine none added < MA chloramine sodium hydroxide cast iron (78%), ductile iron (18%) none added none added MN chloramine Lime softening, blended 18-MN chloramine ortho/polyphosphate cast iron (90%), ductile iron (5%), steel (5%) none added none added AZ chlorine caustic soda ductile iron (majority), copper none added none added < NJ chlorine phosphate 21-NJ chlorine phosphate cement-lined ductile iron (44%), cast iron (41%), asbestos cement (8%) ductile iron (35%), cement-lined cast iron (23%), cast iron (21%), asbestos cement (15%) none added none added none added none added NC Chlorine phosphate PVC (84%), cement-lined ductile iron (13%) chlorine none added MA chloramine sodium bisulfite, soda ash cast iron (29%), steel (24%), cement-lined cast iron (17%), concrete (14%), cement-lined ductile iron (14%) 24-TX chloramine sodium hydroxide PVC (40%), cast iron (32%), ductile iron (15%), reinforced 25-TX chloramine sodium hydroxide concrete (10%) 26-NY chlorine sodium hydroxide phosphoric acid cast iron (33%), cement-lined cast iron (33%), ductile iron (30%) none added none added none added none added >100 chlorine, chloramine none added < This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

9 The facilities were queried to understand current practices for monitoring and control of water stability (Table 4). Most utilities (50 percent) did not have a monitoring program in place specifically for biological stability as shown in Figure 1. Table 4 Monitoring and maintenance/control programs reported by participating utilities Biostability Facility Monitoring Program Water Stability Control Program Biostability Control Program 1-CA chlorine residual, THM, temp, coliforms Work with member agencies to increase flow in stagnant areas, maintain minimum chlorine residual at 1.8 mg/l. May line pipe with carbon fibers none 2-CA chlorine residual, THM, temp, coliforms Work member agencies to increase flow in stagnant areas, maintain minimum chlorine residual at 1.8 mg/l. May line pipe with carbon fibers 3-WI none Flush all hydrants and dead ends to 5 NTU. none 4-WI Sedimentation is evident when a water main breaks and water flows in the opposite direction. 5-CO none Stabilize ph and alkalinity, replace pipes at 0.4% none 6-CO 7-OK taste & odor in raw per year, flush in response to rusty water Flush hydrants as needed none 8-OK water, DBPs, chlorine residual 9-GA coliforms, chlorine Flush hydrants as needed none 10-GA 11-MI residual none none none 12-MI none none none 13-VA HPCs, NO 2 /NO 2, chlorine residuals. Monitor for sedimentation and tuberculation. Unidirectional flushing in parts to cover the whole system in 5 years. Flush when HPC are above 500 CFU/mL Cleaned and lined older pipes flushing 14-OH none flu shining to address customer complaints (isolated none 15-OH 16-MA none events); replace pipes at 1%/yr none none 17-MN nitrate, ammonia, flushing in parts to cover the whole system in 4 flushing 18-MN 19-AZ coliforms Total dissolved years, relined 25% of pipe, replace <1%/yr flush hydrants (formerly weekly), storage tanks none solids, ammonia periodically cleaned out 20-NJ none primarily flushing as needed, none replace pipes at 0.5%/year 21-NJ DBPs, chlorine residual Flush small lines annually and larger lines (>12") every 3 years for sedimentation control none 22-NC ammonia, nitrate, nitrite, chlorine residual, coliforms, HPCs (tuberculation, iron, and manganese deposits) Lend money to communities to line their pipe. Goal to replace/rehab 2-2.5% per year none Education on flushing, results of long HRT and dead ends. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

10 Facility Biostability Water Stability Control Program Biostability 23-MA none Dead end lines are flushed monthly. none 24-TX none Dead end lines are flushed monthly. none 25-TX turbidity, chlorine residual flushing or re-routing of water mains to increase flow in areas with low chlorine residual or higher DBPs. flushing or rerouting of water to decrease water age Note: Monitoring programs reported as none indicate that no program was in place for management of biostability. Figure 1. Monitoring and control programs implemented by utilities for management of biostability. Of the remaining utilities that monitored for biostability, the frequently monitored parameters were disinfectant residual (77 percent), coliforms (54 percent), disinfection byproducts (38 percent), and ammonia (38 percent). Control programs were in place primarily for management of general water stability issues, such as lead and copper rule requirements, sedimentation, and disinfection byproduct formation. Figure 2 shows the type and distribution of control programs typically used, which was primarily flushing of lines. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

11 Figure 2. Control programs implemented by utilities for management of water stability. Flushing rates and durations were highly variable and ranged from 10 to 1200 gpm. Since flushing is typically conducted using hydrants, many utilities were unsure what the flow rates were. Most programs involved unidirectional flushing covering the distribution system in stages over a period of 2 to 5 years. Particular attention was paid to cul-de-sacs and dead end lines. Approximately 27 percent of the utilities reported replacement or lining of pipe was used as a maintenance program. Replacement or lining of pipe is an expensive process that was typically reported as occurring at a rate of less than 1 percent per year. Identification of Water Stability Problems Eleven of the 26 utilities had a recognized issue with biostability either in the past or during current operations based on survey results (Table 5). General rules of thumb reported by utilities as causes for problems with water stability included water corrosivity, temperature, and flow. In areas with more corrosive water, higher temperatures, longer hydraulic retention times, lower disinfectant residual and stagnant zones, the likelihood of problems with bacterial regrowth and/or nitrification were increased. For example, facilities 17-MN and 18-MN used chloramines as a disinfectant. There were problems with nitrification and low chlorine residual during the summer months with warmer temperatures. There were also problems with red water and sedimentation from iron sloughing of cast iron pipes. Cast iron makes up 90 percent of their year-old system. While an accurate hydraulic model was not in place prior to the Phase 2 data collection effort, there were some areas with residence times as long as approximately 14 days. The areas with the longest residence time also had the highest frequency of customer This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

12 Table 5 Historical problems with water stability based on survey results. Facility Historical ID Event? Water Stability Problems Indicators Likely Causes Mitigation Strategy 1-CA N None known NA NA NA 2-CA N None known NA NA NA 3-WI This was a concern in one outlying suburb. A community adjacent to the outlying Raw water temperature, low Y Nitrification in areas with low circulation Warmer lake raw water temps (>15 deg C) in Aug/Sept suburb began receiving water from MiWW and the problem went away. This was most 4-WI chlorine residual likely associated with increased flow to that area. 5-CO 6-CO 7-OK N None known NA NA NA Y Disinfection byproducts and low chlorine residual from AB Jewell Stage 2 DBP rule sampling Sites with longest hydraulic residence time have the highest annual average disinfection byproducts 8-OK 9-GA 10-GA N None known NA NA NA 11-MI N None known NA NA NA 12-MI N None known NA NA NA 13-VA Y (1) Nitrification event 5 years ago (2) Small amounts of sedimentation Customer complaints, low chlorine residual, coliforms, tuberculation of pipes (1) Warmer temperatures, high water demand (2) Bulk of the sediment is from installation and main breaks DBP response: changing disinfectand from free chlorine to chloramines (1) Unknown what worked to fix the problem (2) Cleaning and lining of older pipes 14-OH 15-OH N None known NA NA NA 16-MA N Corrosion/tuberculation Tuberculation Corrosion of older pipes None (1) Nitrate/nitrite increases, 17-MN Increased ph to 9 to meet requirements of lead and copper rule. Since increasing the ph, (1) Nitrification in warmer season decreases in chlorine residual Decreased ph causes iron sloughing from pipes, decreased chlorine Y problems with nitrification and red water have subsided. Flush areas throughout the (2) Red water (2) Customer complaints from residual 18-MN system to cover all portions every four years. discolored red water 19-AZ N None known NA NA NA 20-NJ N None known NA NA NA High HPCs and coliform counts, Algae present in reservoir caused formation of AOC and BDOC 21-NJ Y Bacterial growth and nitrification loss of chlorine residual after ozonation and chlorination (1) Used metal coupons to test (1) Unknown (1) Corrosivity issues in 1990s corrosivity 22-NC Y (2) Dead ends with longer HRT have higher losses of chlorine (2) DBPs (2) Disinfection byproducts are residual high in some spots 23-MA Y Nitrification in mid-1990s during warmer temperatures and increased water demand Customer complaints, water color, coliforms, low chlorine residual Increased chlorine dose to meet demand and state regulatory requirements but did not increase ammonia dose. Chlorine decay was significant such that little or no residual was present in some parts of the system, also resulted in oxidation of organics to form more AOC. Coliforms were detected in >10% of samples in warmest months. Changed treatment process to include ozonation and biological filtration to reduce AOC and BDOC in finished water. Flush dead-ends and cul-de-sacs regularly; changed treatment process to include biological filtration which resulted in 50% less chlorine demand Increased ammonia dose to have stable chloramine residual that would last longer in the distribution system. 24-TX N None known NA NA NA 25-TX N None known NA NA NA 26-NY Y Disinfection byproducts Disinfection byproduct sampling Areas with longer hydraulic residence times during warmer and analysis temperatures Increased flow to areas with stagnant water and longer hydraulic residence times. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

13 complaints for red water. Since increasing the ph to 9 to meet corrosion requirements for the Lead and Copper Rule two years ago, the incidences of red water customer complaints and nitrification have subsided. A regular flushing program was also instituted to cycle through the system every four years. Flushing rates were as high as 1200 gpm. A summary of historical problems with stability from the other utilities are included in Table 5, and are also documented in the databases in Appendix B. In addition to feedback from the utilities during the survey, the historical data was reviewed and compared to preliminary screening criteria listed in Table 1. The criteria were used to decipher what types of water quality issues were most prevalent in the systems based on the historical data provided. The most common issues observed were low chlorine residual, high ph, high turbidity, nitrification, elevated HPCs or coliforms, and elevated disinfection byproducts (Figure 3). Both the survey responses and historical data screening were used to determine which utilities were experiencing particular stability problems and which that were not (Table 6). This was a key component of the selection of sites and is discussed in detail in that section. Note: Those without the problem had concentrations lower than the screening criteria and those with the problem were above the screening criteria. The percent listed above the bar graph indicates the number of utilities that experiment an exceedance of the screening criteria (with problem) divided by the number of utilities that provided data to evaluate (responded). Figure 3. Identification of stability issues in distribution systems based on preliminary screening criteria listed in Table 1. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

14 Table 6 Summary of current problems with stability based on either survey responses or case studies. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

15 Statistical Evaluation The purpose of the statistical evaluation was to identify which parameters were associated with stability. The analysis was conducted on data from 16 of the 26 utilities representing 11 distribution systems. There were several data gaps since all utilities either did not monitor for or did not report all the data that were requested (Table 7). The evaluation results for each utility was summarized into a table showing the associations between potential causes and effects and a list of the key findings are presented in Appendix C. For example, at facilities 9-GA and 10-GA, trihalomethanes were highest in ductile iron pipes, as compared to PVC or asbestos cement (Figure 4). Newer pipes had higher concentrations of trihalomethanes, but higher concentrations were also found in areas with longer hydraulic residence times. It is likely that the newer pipes were from sites in more recently developed subdivisions that were farther away from the treatment plant. We speculate that longer residence times were likely more influential on the formation of disinfection byproducts than pipe age. At facility 13-VA, low total chlorine residuals were associated with lower flow rates and higher temperatures (Figure 5). Lower flow rates were also associated with higher hydraulic residence times and higher concentrations of HPCs. The lower residuals allow for growth of organisms, particularly in areas with longer retention times and lower water velocity (Dolan and Pipes 1988). A compounding factor that likely exacerbated the growth of HPCs were reduced chlorine to ammonia ratios in the finished water (<5:1). Facility 13-VA uses chloramines for disinfection and they typically maintain a chlorine to ammonia ratio of greater than 5:1. A chlorine-to-ammonia ratio of up to 5:1 is generally preferred at the finished water to minimize free ammonia available for nitrification (Fiske, Oppenheimer, and Heimel 2010). When the facility had ratios of less than 5:1, the frequency of HPCs greater than 300 CFU/mL significantly increased. At facility 22-NC, HPCs were found to be higher at higher water temperatures, while the total organic carbon (TOC) was lower with a wider distribution during that period (Figure 6). This could be that organisms were utilizing the organic carbon thus resulting in lower concentrations of TOC measured at monitoring points during that timeframe. However, the finished water TOC concentrations were not provided for comparison, so this association is speculative. The associations between causes and effects on water stability were summarized for all of the utilities to determine which parameters were more commonly associated with stability and are summarized in Table 8. The data were broken up into causes of stability or instability and effects. The causes were either from the facility characteristics such as doses of disinfectant, corrosion inhibitor, ph or alkalinity stabilizers; distribution system characteristics such as materials of construction and average hydraulic residence time; water quality in treated and distribution system monitoring points such as chlorine residual and concentrations of organics or nutrients. Effects of water instability included bacterial regrowth (e.g. increases in coliforms or HPCs), nitrification (e.g. decreases in ammonia, increases in nitrate, formation or increases in nitrite formation), disinfection byproduct formation, and disinfectant residual stability. While bacterial regrowth, nitrification, and disinfectant residual stability are important for biological stability, the formation of high concentrations of disinfection byproducts is an undesired This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

16 consequence of disinfection. Therefore, disinfection byproducts were included as part of the evaluation. Table 7 Historical data provided by utilities that were used for the statistical evaluation. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

17 TTHMs, µg/l TTHMs, µg/l Asbestos Cement Ductile Iron Poly Vinyl Chloride Unknown n=4 n=32 n=10 n=10 Pipe Material Unknown n=32 n=10 n=4 n=10 Pipe Age (yrs) TTHMs, µg/l TTHMs, µg/l High HRT Low HRT Unknown < 15 Deg C > 15 Deg C Unknown n=22 n=24 n=10 n=3 n=36 n=17 Redidence Time Mon Pt Note: THMs are the reported total of the four chlorinated and brominated trihalomethanes Figure 4. Selected statistical analysis results from facilities 9-GA and 10-GA. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

18 Cl2 Residual, total (mg/l) HPC (CFU/mL) High Flow Low Flow n=567 n=693 Flow Rate 0 High Flow Low Flow n=567 n=692 Flow Rate Cl2 Residual, total (mg/l) < 15 Deg C > 15 Deg C n=434 n=826 Notes: HRT is hydraulic residence time, Cl2 is chlorine Figure 5. Selected statistical analysis results from facility 13-VA. HPC (CFU/mL) < 5:1 > 5:1 n=755 n=505 Ratio of Chlorine:Ammonia This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

19 HPC (CFU/mL) TOC (mg/l) < 15 Deg C > 15 Deg C Unknown n = 454 n = 972 n = 1432 Notes: HPC is heterotrophic plate count, TOC is total organic carbon Figure 6. Selected statistical analysis results from facility 22-NC. < 15 Deg C > 15 Deg C Unknown n = 19 n = 59 n = 78 This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

20 Table 8 Potential causes for water instability in the distribution system. The associations between causes and effects on water stability are graphically represented in Figures 7 to 10. The primary causes observed between various factors affecting stability were identified as those that were observed at least 50 percent of the time and reviewed at a minimum of two distribution systems. A sub-set of the primary causes were consistently identified for the end-point effects of bacterial regrowth, nitrification, disinfection byproduct formation, and disinfectant residual stability. The primary causes included finished water chlorine dose, finished water free chlorine, hydraulic residence time, pipe material, the monitoring point temperature, and monitoring point free chlorine (Figure 11). While many variables are at play when attempting to interpret these associations, the results provide a valuable initial guide for important factors that influence stability. These importance and interaction of these variables will be further refined in Phase 4. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

21 Figure 7. Associations between bacterial regrowth and Figure 8. Associations between nitrification and various various parameters. parameters. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

22 Figure 9. Associations between disinfection byproduct Figure 10. Associations between disinfectant residual formation and various parameters. stability and various parameters. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

23 Figure 11. Associations between primary potential causes and water stability effects. AOC and BDOC Sampling Samples were collected from the finished water for analysis of AOC and BDOC. AOC values ranged from 43 to 1293 µg acetate-c/l. Concentrations were highest in the two unfiltered treatment systems, facility 23-MA and 26-NY. Facility 23-MA had significantly higher concentrations of AOC, 1293 µg/l, as compared to the remaining facilities. Facility 23-MA was the only facility to use ozone as the only treatment process for water collected from a reservoir. Facility 23-MA also has a long history of managing problems with biological stability due to the large size and age of their distribution system. In contrast, facility 7-OK had the lowest concentration of AOC in the finished water and was the only utility to not exhibit any stability problems. The incidence of elevated HPCs (greater than 100 CFU/mL) or detections of coliforms was greater at facilities with AOC concentrations exceeding approximately 100 µg acetate-c/l. These findings are consistent with previous research demonstrating that AOC levels greater than 100 µg acetate-c/l had increased incidences of coliform bacteria (Camper et al. 2000). BDOC concentrations ranged from below detection to 1.16 mg/l, with the highest concentrations measured at facility 23-MA. As noted above, facility 23-MA has had several incidences of biostability issues, some of which are ongoing. The lowest concentrations corresponded to utilities that reported little or no incidences of historical biostability problems. For example, facilities 14-OH and 15-OH facilities and the facility 8-OK never had issues with bacterial regrowth or nitrification. These facilities did have some elevated disinfection byproducts reported but no historical problems with bacterial regrowth or nitrification. Results of the AOC and BDOC sampling is shown below in Table 9 This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

24 Table 9 Ranked Phase II Organic Carbon Sampling Results Facility ID AOC (µg/l) DOC (mg/l) BDOC (mg/l) 23-MA 1, NY MA GA NJ GA TX TX MI CO WI CA CO CA VA WI OH < OH < AZ OK MI NJ OK Note: shaded entries denote systems selected for Phase IV field testing Phase 3 Selection of Sites for Full-Scale Monitoring The 26 facilities that participated in Phase 2 were evaluated to determine which would be selected for the Phase 4 full-scale monitoring program (Table 10). There were four facilities that did not agree to participate in Phase 4. Of the remaining 22 utilities, there were five facilities that did not have a working hydraulic model of their system. While many parameters are being evaluated in this study, a key component to the program design is understanding the effect of hydraulic residence time. Therefore utilities that did not have a method for determining water age (either through a tracer study or working hydraulic model) were not considered for selection. Of the 17 utilities that agreed to participate and could quantify the hydraulic residence time, there were three utilities that had two facilities with that fed into a single distribution system. One of those facilities was removed to increase the diversity of systems represented. For example, facilities 14-OH and 15-OH were both participating in the study. Facility 15-OH was not This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.

25 selected for further analysis because the source water quality (groundwater) was of higher quality than 14-OH (river water source). Finally, due to the rigorous level of commitment needed by the utility partner for successful completion of this study, those utilities that were most responsive during the Phase 2 data collection effort and sampling program were included. The lack of responsiveness was in most cases associated with commitments on other major endeavors. For example, facility 22-NC was undergoing a major expansion at their facility and as such would not provide an ideal setting for data collection or interpretation. This preliminary screening of utilities resulted in a subset of 10 systems to evaluate for participation in Phase 4. The subset of 10 systems included: 7-OK 9-GA 11-MI 13-VA 14-OH 16-MA 20-NJ 21-NJ 23-MA 26-NY Table 10 Summary of potential utilities for participation in Phase 4 Notes: 1. Biostability problems were identified as bacterial regrowth (elevated HPCs or coliforms) or nitrification. 2. Stability problems were identified as all other water stability problems listed in Table 6 that were identified during the survey and historical data review. This information has not been reviewed by WaterRF to determine whether it contains patentable subject matter or third-party copyrighted materials, nor has the accuracy of its information or conclusions been evaluated. Accordingly, the information is not considered published and is not available for general distribution. Until the information had been reviewed and evaluated by WaterRF, it should not be disclosed to others to reproduce, wholly or partially, without the written consent of WaterRF Water Research Foundation. ALL RIGHTS RESERVED. No part of this content may be copied, reproduced or otherwise utilized without permission.