Technology Primers for the Simultaneous Compliance Tool

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1 Technology Primers for the Simultaneous Compliance Tool Supplement to #91263 Subject Area: Water Quality

2 NEW CHLORINE APPLICATION Chlorine is the most widely used disinfectant in water treatment primarily due to its low costs and relative ease of operation. Chlorine is typically used as a primary disinfectant for the inactivation of microorganisms and as a secondary disinfectant to maintain chlorine residual levels in the distribution system to minimize biological regrowth. For these reasons, chlorine is often used to comply with the requirements of the Surface Water Treatment Rules and Total Coliform Rule. In addition to the disinfecting capabilities, chlorine is a strong oxidizing agent that is used in various water treatment processes such as color removal. Addition of chlorine to water produces hypochlorous acid (HOCl), and various byproducts depending on the type of chlorine used. Chlorine is commercially available in the form of compressed elemental gas (Cl 2 ), liquid solutions of sodium hypochlorite (NaOCl), and solid calcium hypochlorite (Ca(OCl) 2 ). NaOCl can also be generated on-site by electrolysis of brine solutions. The brine solution, which is formed by the combination of granulated salt and softened water, is delivered to an electrolytic cell where NaOCl and hydrogen gas are formed. Gaseous chlorine is typically injected into a carrier water stream before injection into the process. The dry forms are typically used to create a saturated hypochlorite solution that is then injected into the process. The liquid forms, whether purchased as a bulk sodium hypochlorite solution are generated on-site, are injected directly into the process. Chlorine reacts with inorganic and organic compounds in the source water. In general, the compounds are oxidized to form other compounds. In the case of microorganisms, chlorine reacts with the critical components of the organism to cause inactivitation. The effectiveness of chlorination is dependent on dose, contact time, ph, and temperature. There are a number of potential unintended consequences related to chlorination. Consequences include taste and odor complaints, formation of disinfection byproducts (DBPs), changes in the corrosivity of treated water, precipitation of iron/manganese that leads to color changes of the water, security and safety issues of new chemical, and compatibility with existing technologies. Addition of a new chlorination process into an existing drinking water system may result in taste and odor complaints with customers who may not have had prior exposure to chlorinated water. Chlorinous taste and odor may be detected in systems with low residual levels in the distribution system and more prominently in systems with high levels. Additional taste and odor complaints may occur when the source water is obtained from surface waters due to the presence of algae and other organic matter reacting with the chlorine. Prior to implementation, proper communication with customers noting the addition of the new chlorination system to increase the safety of the treated water should be undertaken to avoid customer complaints. In addition steps should be taken to minimize the chlorine residual levels in the system without compromising the microbial control. Formation of chlorinated DBPs, some of which are regulated such as trihalomethanes and haloacetic acids, occurs when chlorine reacts with organic matter in the water. DBPs must be must be monitored at the plant effluent and at

3 agreed upon locations (with the regulatory agency) throughout the distribution system. If DBP levels exceed compliance levels, additional treatment processes, such as coagulation, adsorption, etc., may need to be implemented at the treatment plant. The use of sodium hypochlorite for disinfection may introduce additional DBPs due to the possible presence of impurities in the chemical. Impurities can include bromate, chlorite, chlorate, etc. To minimize the concentrations of these additional DBPs, proper design and chemical selection should be practiced. Addition of chlorination alters the oxidation-reduction potential of the treated water; possibly impacting the corrosivity of the water. In some cases the addition of chlorine may result in sloughing off of some existing corrosion byproducts from inside the distribution system pipes. Chlorinated water may also increase the corrosion of household copper plumbing due to the increased oxidation-reduction potential. If corrosion is observed, an evaluation will need to be performed to determine the best method to control corrosion in the system, for example, the addition of a corrosion inhibitor (e.g., orthophosphate) at the treatment plant. Chlorine oxidizes dissolved iron and manganese in the source water, which precipitates and can be seen as color in the water when the source concentration is high enough. The addition of a filtration system after chlorine addition can remove the precipitated iron and manganese from the treated water. Additional safety and security measures must be implemented when a new chlorination system is installed. The chlorination system (gas chlorination system, liquid chlorination system, or onsite generation system) must be properly designed and constructed to ensure proper chemical handling by the operators. Proper containment and safety procedures need to be implemented to ensure the safety of people in the surrounding area in case the accidental release of a gas chlorine and hazardous liquid chlorine. Design and construction of a new chlorination system must be coordinated with the existing technologies at the water treatment plant to ensure the technology is compatible with the existing treatment process. Additional coordination is required to ensure compatibility with the distribution system. Combining waters in the distribution system that utilize different disinfectants (none, chlorine, and/or chloramines) may impact the water quality of the treated water. Water providers must communicate with each other prior to implementation of new treatment systems. Approximate capital and O&M costs are provided in Table 1. Table 1. Approximate Costs of Addition of New Chlorine Feed System Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.50 $0.20 $0.10 $0.10 Annual O&M Cost ($/kgal) 2 $4.00 $1.30 $0.20 $ Costs assume use of sodium hypochlorite. Capital costs are based on $ per gallon of treatment capacity. For example, addition of a new chlorine system at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $15,000 ($1.50/gal 10,000 gal = $15,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $7,300 ($4.00/kgal 5 kgal/day 365 days/year = $7,300).

4 OPTIMIZATION OF CHLORINATION PRACTICES Optimizing chlorination practices can be an effective strategy to reduce disinfection byproducts. It includes several strategies: Eliminate pre-chlorination. Move the point of chlorine addition. Optimize chlorine dose. Reduce chlorination ph. Eliminating pre-chlorination can be particularly effective for the control of disinfection byproducts (DBPs). However, failure to replace chlorine with an alternative pre-oxidant, such as potassium permanganate, can result in several process upsets. Algae, taste and odor, iron and manganese, and other contaminants for which pre-chlorination was effective may now pass through the treatment process. Further, failure to maintain oxidizing conditions in the filters can result in desorption of manganese dioxide and cause pink or yellow water problems in the distribution system. Where primary disinfection credit is awarded for prechlorination, alternate disinfection strategies need to be installed prior to elimination of pre-chlorination. Moving the point of chlorination further downstream in the treatment processes, for example, after sedimentation/clarification, can also be an effective strategy for reducing DBPs. Delaying chlorine addition until after coagulated material, including natural organic matter (NOM), is removed from the process minimizes the concentration of DBP precursors present and reduces DBP formation. Again, where primary disinfection credit is awarded for prechlorination or chlorination helps to control other contaminants, this practice should be carefully evaluated. distribution system. There are several strategies to do this, including: Minimizing the pre-chlorine dose to that needed for pre-oxidation and applying what is needed for primary disinfection after the filters rather than adding all of the chlorine prior to the filters. Reducing the secondary chlorine dose (that prior to the system) to maintain minimal ( mg/l) chlorine levels in the distribution system. Optimizing the chlorine dose, particularly by reducing the dose entering the distribution system can be difficult. Reducing the dose by too much may result in areas of the distribution system with no residual causing taste and odor, color, biofilm growth, corrosion, or other water quality problems. With free chlorine, the dose required for primary disinfection is directly proportional to the chlorination ph. That is, lower CT values are required at lower ph values. Thus, by reducing the chlorination ph, the primary chlorine dose can be reduced and may result in reductions in DBP levels. It may be necessary to re-adjust the ph prior to distribution to eliminate the potential for any negative impacts on system corrosion. It also should be noted that changes in the chlorination ph may cause a shift in the speciation of DBPs specifically an increase in haloacetic acid formation. Optimizing chlorination practices can be an effective strategy to reduce DBPs for many systems. However, prior to implementing any such changes, the effects on treatment efficacy, primary disinfection, corrosion control effectiveness, and shifts in DBP speciation should be evaluated. The cost of optimization of chlorination practices is extremely site specific. No generalized cost can be provided. Optimizing the chlorine dose can also be an effective way to reduce DBP levels in the

5 CHEMICAL SEQUESTRATION Chemical sequestration is a method used in water treatment to control metals release and other factors that influence water quality. Chemical sequestering agents do not prevent corrosion so much as they prevent corrosion byproducts from precipitating and causing color or other aesthetic issues. Chemicals used for sequestration purpose bind up targeted compounds to prevent reactions that normally that cause corrosion in the piping of the distribution system. Corrosion inhibitors form a protective, relatively insoluble film on the inside surface of the pipe to act as a barrier between the water and the pipe surface and prevent dissolution or release of metals (e.g., lead, copper, or iron) from the pipe wall. Sequestration is generally used for control of red water and other aesthetic problems, whereas corrosion inhibitors are primarily used for compliance with the Lead and Copper Rule. The most common chemical sequestering agents are polyphosphates, and include polyphosphates, glassy phosphates, and hexametaphosphate. Most corrosion inhibitors are also phosphate-based, but are generally of the orthophosphate variety (e.g., phosphoric acid, orthophosphate, or zinc orthophosphate). Orthophosphate/polyphosphate blends are also frequently used to achieve the benefit of both chemical sequestration and corrosion inhibition. To ensure effectiveness of the sequestering/ inhibiting agent, selection of the type of agent is important. For example, polyphosphates can be used as a sequestering agent for iron and control of red water, prevention of calcium carbonate scaling, but should not be used for lead control. On the other hand, orthophosphate can be very effective for the control of lead and copper corrosion, but polyphosphates generally result in increased corrosion of these metals. Selection of an agent is dependent on the water system, operational conditions, water quality of the distribution system, and particular water quality concerns. The operational effectiveness of chemical sequestering agents is dependent on the dose, feeding and flow rates. There are a number of potential unintended consequences related to chemical sequestration, including increased lead and copper corrosion in the distribution system, regrowth in the distribution system, sloughing off contaminants in the distribution system, physical integrity of the distribution system, and increased zinc and phosphorus loading to wastewater treatment plants and receiving waters. The use of polyphosphates as a chemical sequestering agent may cause lead and copper corrosion in the distribution system. The combination of high doses of polyphosphate and new household plumbing may result in the increased copper corrosion and failures in household plumbing. If lead and copper are present, the use of an orthophosphate/polyphosphate blend should be considered to maintain the objectives of chemical sequestration and corrosion control. The water provider should take care in introducing phosphate as a sequestering agent and implement the addition in stages to minimize the impact of the change on the distribution system corrosion. Phosphorus, present in phosphate, is an essential nutrient for biological growth. Addition of phosphate at a water treatment plant may encourage biological regrowth inside a distribution system, which may result in difficulty in

6 maintaining disinfectant residuals, increased taste and odor, and possible microbiologically-influenced corrosion of household plumbing. Regrowth in a system is more prominent in areas with relatively aged distribution systems coupled with high phosphate doses. It will be necessary to monitor the system and adjust the treatment as necessary to manage the level of regrowth in the system. In conjunction with regrowth possibilities, sloughing off of the biofilm may be a potential issue. Due to pipe hydraulics, regrowth on the inner surfaces of the piping may slough off and become present at customer taps. Approximate capital and operations and maintenance (O&M) costs are provided in Table 1. Table 1. Approximate Costs of Chemical Sequestration Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.00 $0.15 $0.10 $0.05 Annual O&M Cost ($/kgal) 2 $0.20 $0.10 $0.05 $ Costs assume the use of polyphosphate. Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of chemical sequestering at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $10,000 ($1.00/gal 10,000 gal = $10,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $400 ($0.20/kgal 5 kgal/day 365 days/year = $365). Wastewater treatment plants limit the amount of zinc and phosphorus they can accept because it may adversely impact the wastewater treatment process and the water quality of the receiving water bodies that the treated wastewater is discharged; therefore, the sequestering agent should be dosed at a level to obtain the desired corrosion control results as well as be at levels acceptable to the wastewater treatment plant. The water provider should communicate with the wastewater treatment plants prior to the implementation of the corrosion control system to ensure that the wastewater treatment process is not adversely impacted.

7 ULTRAVIOLET DISINFECTION Ultraviolet (UV) light can be used for the inactivation of drinking water pathogens or in combination with hydrogen peroxide as an advanced oxidation process for the oxidation of micropollutants. In the latter capacity, it is commonly used. UV disinfection or oxidation is a physical process that utilizes UV light and does not require addition of any chemicals. This technology is known for its germicidal power in inactivating microorganisms (i.e. bacteria, viruses, algae, etc.) including chlorineresistant pathogens, such as Cryptosporidium. However, its use in advanced oxidation processes is increasing. Coagulant Rapid Mix Flocculation/ Sedimentation Filtration Interstage Pumping Caustic UV Light Storage UV disinfection uses UV light to inactivate pathogens by disrupting their DNA strands making them non-viable and non-infectious. UV light is generated by flowing electrons from an electrical source through ionized mercury vapor. UV lamps commonly used in drinking water treatment are classified as low-pressure (LP) lamps, low-pressure high output (LP-HO) lamps, and mediumpressure (MP) lamps. LP-HO lamps have special design features that allow for higher UV radiation transmittance and are therefore more efficient than MP lamps. MP lamps produce 10 to 20 times higher UV radiation outputs than LP and LP-HO lamps; thereby requiring fewer lamps and decreased maintenance. However, power requirements are significantly higher and higher temperatures generated can cause scaling of sleeves in some waters. LP and LP-HO systems are typically better suited for small and medium sized systems because of their reliability associated with operating with multiple lamps. The UV dosage applied for inactivation is a function of UV irradiance and exposure time (intensity time, IT) and is analogous to the CT term used in for chemical disinfectants. Since UV dose is primarily based on light intensity, water quality parameters such as turbidity and suspended solids (SS) can lower UV transmittance by screening/shielding UV light from the microorganisms. The presence of some organic and inorganic compounds (such as iron, calcium, hardness, etc.) can also absorb UV light, lowering UV transmittance. Water quality parameters such as ph, alkalinity, and temperature do not impact the overall effectiveness of UV disinfection. However, these parameters can affect scaling of UV lamp sleeves. UV lamp sleeves require periodic cleaning to remove biological and chemical fouling materials that decrease the intensity of the lamps. Mercury is contained within UV lamps, and design provisions should be made to assure that no mercury is released from the treatment plant in the event a lamp is broken. The potential for mercury release as a result of lamp breakage is very small. UV disinfection has a low potential to form by-products because the intensities used are less than those required to cause photochemical reactions. UV irradiation has the advantage that it does not add or remove anything to change the water chemistry and only requires a very short contact time; however, because UV irradiation does not leave a residual, a second disinfectant must be added to leave a residual in the distribution system. One of the most significant factors impacting UV system operation is power quality. Compared with conventional chemical disinfection methods, UV disinfection requires a significant amount of electrical power. Fluctuations in the power quality have the potential to disrupt disinfection and could jeopardize compliance with

8 disinfection requirements. A power quality study and appropriate engineering design considerations, such as upgrades to the power supply or use of uninterrupted power supply (UPS), can help to minimize the impacts of power quality on system performance and reduce the potential for declines in disinfection efficacy. Approximate capital and operations and maintenance (O&M) costs for a UV disinfection system are provided in Table 1. Capital costs are based on a dose of 40 mj/cm2 and include an uninterruptible power supply (UPS), electrical and instrumentation and controls. O&M costs include power, replacement lamps and sleeves, and maintenance labor. Table 1. Approximate Costs of Ultraviolet Disinfection Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.5 $0.30 $0.25 $0.10 $0.07 Annual O&M Cost ($/kgal) 2 $2.00 $0.50 $0.10 $0.05 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of UV disinfection at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $15,000 ($1.50/gal 10,000 gal = $15,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $3,650 ($2.00/kgal 5 kgal/day 365 days/year = $3,650). O&M costs do not include the current $0.015/1000 gal patent fee.

9 ENHANCED COAGULATION Enhanced coagulation is now widely practiced for removing DBP precursors, and can also removes inorganic, particulate, and color causing compounds. It includes several optimization strategies: Increase coagulant dose. Reduce coagulation ph. Reduce coagulation ph and increase dose. Change coagulant with/without the above. In coagulation, a positively charged coagulant (usually an alumimum or iron salt) is added to raw water and mixed in the rapid mix chamber. The coagulant alters or destabilizes negatively charged particulate, dissolved, and colloidal contaminants. The optimal ph range for coagulation is 6-7 when using alum and when using iron. For high alkalinity water, excessive amounts of coagulant may be needed to lower the ph to the optimal ph range. In these cases, it may be beneficial to use acid in addition to the coagulant to reduce the amount of coagulant needed and effectively lower chemical costs. Reducing the coagulation ph, increasing the coagulant dose, or changing coagulants can affect finished water stability and corrosion control effectiveness. It is important that any reduction in coagulation ph be adequately re-adjusted prior to distribution to minimize the potential for increased lead, copper, or iron corrosion. Increased alum or ferric salt doses can result in increased concentrations of dissolved aluminum and iron in the distribution system. Excess iron may precipitate in the distribution system causing red water. Residual aluminum can cause formation of aluminum precipitates, reducing hydraulic capacity, and increasing operations costs. Residual aluminum has also been demonstrated to be a factor in increased copper corrosion in home plumbing. Coagulant changes from alum to ferric chloride may cause an increase in the finished water chloride-to-sulfate ratio which has been demonstrated to increase lead corrosion in some distribution systems. Using ferric sulfate, and/or the use of a corrosion inhibitor, has been shown to minimize these impacts. Enhanced coagulation may increase the quantity or change the characteristics of the residuals generated. Coagulation sludge will contain elevated concentrations of contaminants removed during the treatment process. Depending on the source water concentration of a particular contaminant and any disposal limitations, it may be necessary evaluate the disposal of process solids with respect to state and local hazardous waste regulations. Approximate capital and operations and maintenance (O&M) costs for enhanced coagulation are provided in Table 1. Costs are based on an additional coagulant (alum or ferric) dose of 56.5 mg/l and additional caustic dose of 25 mg/l (to adjust the finished water ph to its original level). Costs assume a coagulant and caustic feed system are present and only need upgraded. Capital costs include upgrades to existing chemical feed systems, piping and valves, and instrumentation and controls. O&M costs include chemicals, power, replacement parts, and maintenance labor. Table 1. Approximate Costs of Enhanced Coagulation Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $0.20 $0.10 $0.05 $0.02 $0.01 Annual O&M Cost ($/kgal) 2 $0.60 $0.30 $0.25 $0.20 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of enhanced coagulation at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $2,000 ($0.20/gal 10,000 gal = $2,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $1,095 ($0.60/kgal 5 kgal/day 365 days/year = $1,095).

10 MICROFILTRATION/ULTRAFILTRATION Microfiltration (MF) and ultrafiltration (UF) are membrane filtration processes commonly used in water treatment. MF and UF are typically applied for the removal of particulate and microbial contaminants, and are frequently used as an alternative to rapid sand filtration in conventional treatment and softening applications. The primary difference between MF and UF is the pore size of the membranes. Both MF and UF membranes are primarily used for particulate and microbiological contaminant removal. Particulates removed include suspended solids, turbidity, some colloids, bacteria, protozoan cysts, and viruses (only UF has been demonstrated to remove viruses to any significant degree). Inorganic chemicals (e.g., phosphorus, hardness and metals) may be removed with suitable pretreatment. Limited dissolved organics removal may also occur by either of these processes. MF and UF membrane systems frequently require some type of source water pretreatment to prevent membrane fouling. The type of pretreatment required depends on the feed water quality and membrane type. Generally, surface water requires more extensive pretreatment than groundwater due to higher suspended solids and biological matter content. Water temperature has a significant impact on water density and viscosity, which impacts MF and UF membrane performance. As the viscosity and density increase, the transmembrane pressure required to pass the water through the membrane also increases. Both MF and UF membrane systems include routine backwashing to remove foulants from the membrane. Backwash frequency and duration depend on the membrane system and specific feed water quality conditions and treatment requirements. Chemical clean-in-place (CIP) is used periodically to control membrane fouling. Residuals generated from MF and UF systems include the spent backwash and spent cleaning solutions. Spent backwash may be recycled to the process to increase system recovery, reduce chemical doses, and improve overall treatment performance. Otherwise, disposal of spent backwash is generally accomplished by discharge to a sanitary sewer or receiving stream, much the way spent backwash from a rapid sand filter would be handled. Spent cleaning solutions are generally acidic in nature and require neutralization prior to disposal. Approximate capital costs for MF and UF systems are provided in Table 1. Capital costs do not include pre-treatment or posttreatment processes because they are highly dependent on the specific source water quality. O&M costs include power, replacement parts, membrane replacement, CIP chemicals, and maintenance labor. Table 1. Approximate Costs of Membrane Filtration Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $18.00 $4.30 $1.60 $1.10 $0.85 Annual O&M Cost ($/kgal) 2 $4.25 $1.10 $0.60 $0.30 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of membrane filtration at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $180,000 ($18.00/gal 10,000 gal = $180,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $7,756 ($4.25/kgal 5 kgal/day 365 days/year = $7,756).

11 NON-GAC ADSORPTION PROCESS Adsorption is a physical-chemical process in which contaminants accumulate and adsorb onto the adsorbent surface as water passes through the absorbent. Adsorbent materials are subdivided into two major categories: carbon-based (such as granular activated carbon or GAC) and non-carbon based materials. Non- GAC adsorption processes can be used to remove inorganic contaminants, such as arsenic, chromium, and perchlorate, endocrine disrupting chemicals (EDCs), and pharmaceuticals and personal care products (PPCPs). Non-GAC adsorption is most commonly used to comply with the Arsenic and Radionuclides rules. Inorganic contaminants are removed from the water in two ways: electrostatic/physical attraction or chemical attraction. Electrostatic/ physical attraction, also known as Van der Waals forces, physically attracts the contaminant ion in the water to the adsorbent surface. Chemical attraction chemically bonds the targeted contaminant ion to the adsorptive media. There are a number of non-carbon adsorbent materials available, such as activated alumina, granular ferric hydroxide, sulfur-modified iron, and other specialty adsorbents. The effectiveness of the adsorptive media depends on the concentration of the target contaminant ion, operating ph, presence of other competing ions, surface-charge of the adsorbents, physical-chemical characteristics of the adsorbent, time and flow characteristics. There are a number of potential unintended consequences related to non- GAC adsorption. Consequences include the reduction of disinfectant demand, altered corrosion conditions in the distribution system, and altered preoxidation needs. In addition to removal of arsenic and other inorganic contaminants, non-gac adsorption may also remove other materials in the water that exert a chlorine demand, reducing the chlorine demand of the water. The operator will need to monitor and adjust the disinfectant doses to prevent overdosing of chlorine and maintain reasonable levels of residual in the distribution system. The stability of the treated water may also be altered by the removal of certain inorganic constituents, such as calcium or sulfate, by the adsorption process. Changes in alkalinity or shifts in the chloride-to-sulfate mass ratio can impact the stability of the finished water and lead to dissolution of existing pipe scales or increases in corrosivity. Changes that cause dissolution of existing scales are more likely to impact older areas of the distribution system. Shifts in the chloride-to-sulfate mass ratio are most likely to impact areas with lead service lines and newer homes with copper plumbing. Proper operations and appropriate monitoring should be implemented to ensure corrosion issues do not arise. If issues do occur, addition of a corrosion inhibitor should be included into the treatment process to mitigate the problem. If a treatment plant utilizes preoxidation chemical, the application point of the chemical relative to the location of the adsorption technology should be taken into consideration. The preoxidation chemical may alter the effectiveness of the adsorption technology if fed upstream of the process. In some media, chlorine (as hypochlorite (as OCl - )) or permanganate (as MnO 4 -) may compete for adsorption sites and reduce removal of the targeted contaminant. Therefore, the application point of the preoxidation

12 chemical may need to be moved, especially if the system uses high doses of the chemical. Aeration of hard groundwaters upstream of an adsorbent could result in calcium carbonate precipitation and scaling in the media. Non-GAC adsorption is an alternative technology used to remove inorganic contaminants. Approximate capital and operation and maintenance (O&M) costs are provided in Table 1. Capital costs include the chemical feed system with associated piping, valves, and storage and instrumentation and controls. O&M costs include replacement of media, labor, and energy. Table 1. Approximate Costs of Non-GAC Adsorption Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $2.00 $1.00 $0.50 $0.50 Annual O&M Cost ($/kgal) 2 $3.00 $1.00 $0.75 $ Costs are based on activated alumina and are expected to be consistent with other non-gac adsorption processes, such as granular ferric hydroxide (GFH). Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of non-gac adsorption at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $20,000 ($2.00/gal 10,000 gal = $20,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $5,500 ($3.00/kgal 5 kgal/day 365 days/year = $5,475).

13 AERATION AND AIR STRIPPING Aeration and air stripping technologies are used for a variety of water treatment applications including the oxidation and removal of metals, volatile organic compounds (VOCs), volatile disinfection byproducts, and hydrogen sulfide. Air stripping is most commonly used for compliance with VOC regulations; whereas aeration is commonly used as an oxidation technology for iron and manganese removal and taste and odor control (e.g., hydrogen sulfide oxidation). Contaminant Influent Packing Material Packing Support Gas out to atmosphere or secondary treatment Air In Spray Packing Restrainer Liquid Redistributors Packed Column Blower Assembly Aeration is a process in which air or oxygen is transferred to water and air stripping is the process in which gas is removed from water. These treatment processes are based on the principle of Henry s Law, which is described as the tendency of a constituent to transfer from the liquid to the gas phase at equilibrium. The Henry s Law constant is the ratio of the equilibrium concentration of a particular contaminant in air to its concentration in water; therefore, the larger the constant the greater the tendency for that contaminant to volatize. There are four general categories of aeration and air stripping methods: waterfall aeration (i.e., spray aeration, cascade aeration, tray aeration, etc.), bubble aeration, mechanical aeration, and pressure aeration. The effectiveness of aeration and air stripping depends on the method selected, the Henry s law constant of the contaminant, design factors such as air-to-water ratio, flow and loading rate, available area of mass transfer, temperature, ph, and algae production/fouling of the aerator. Influent Treated Effluent Typical Packed Tower (Waterfall) Aeration Typical Diffused (Bubble) Aeration Compressor Diffuser Effluent There are a number of potential unintended consequences related to aeration and air stripping, including scale formation in downstream piping, valves, and process equipment, difficulty in maintaining oxidant/disinfectant residuals downstream of the aeration process, possible need to add disinfection sloughing off of contaminants in the distribution system, loss of physical integrity of the distribution system (leaks), colored water complaints, and biological regrowth in the system due to additional dissolved oxygen.

14 Aeration and air stripping remove dissolved carbon dioxide (CO 2 ) from the source water resulting in increased ph levels. Depending on the hardness of the water, the increased ph levels may form calcium carbonate scale in downstream piping, valves, and process equipment; the harder the water, the more scale is formed. If a filter system is located downstream, the scale formation can result in cementing of the filter media. To eliminate the potential of scale formation, additional treatment can be implemented to remove the hardness (softening), prevent scale formation (chemical sequestration), or reduce the ph. Aeration and air stripping can form particulate iron by oxidizing dissolved iron in the water resulting in red water. This is more evident in waters with higher iron concentrations in the water. To avoid red water complaints from customers, addition of a filtration system downstream of the aeration process can prevent the release of the particulate iron into the distribution system. Dissolved oxygen concentrations increase as a result of the aeration and air stripping process. As a result, microbial regrowth in the distribution system can occur. The increased biological activity is more prominent in older distribution systems and systems with unlined cast iron or galvanized iron pipe since these systems are more likely to show higher tuberculation, which generally consist of larger microbiological populations. In some cases, these growths may slough off and appear at the customers taps. increase with the higher dissolved oxygen concentration levels, particularly in areas with low disinfectant residuals. The increase in activity may result in microbiologically-influenced corrosion in home plumbing causing leaks. Reduction in disinfectant residuals may occur if aeration and air stripping is located downstream of the disinfectant application point. Typically the aeration process is located prior to the disinfectant addition unless the process is used to remove volatile disinfection byproducts. Approximate capital and operations and maintenance (O&M) costs are provided in Table 1. Table 1. Approximate Costs of Aeration Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $10.00 $1.50 $0.20 $0.10 Annual O&M Cost ($/kgal) 2 $5.50 $1.50 $0.20 $ Costs assume packed tower aeration which represents the high end of aeration costs. Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of aeration at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $100,000 ($10.00/gal 10,000 gal = $100,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $10,000 ($5.50/kgal 5 kgal/day 365 days/year = $10,037.50). Potential leaks in the piping are another possible consequence. Increased dissolved oxygen concentrations may increase pitting corrosion in copper plumbing, which is more susceptible in the plumbing of newer homes. Microbial activity in the distribution system may

15 OXIDATION AND PRESSURE FILTRATION Oxidation and filtration is an effective method in removing both organic and inorganic contaminants from water. Oxidation converts the dissolved inorganic substances to insoluble particulates, which are then removed from the water by filtration. For this reason, it is most frequently used for iron removal. It can also be used to comply with the turbidity and disinfection requirements of the Long Term 2 Enhanced Surface Water Treatment Rule. Oxidants typically used in water treatment include chlorine, chlorine dioxide, potassium permanganate, and ozone. Oxidation is the chemical process of changing the soluble inorganic species into insoluble precipitates. Effectiveness of the oxidation process depends on water chemistry (e.g. ph, concentration of soluble species) and the chemical dose of the added oxidants. Filtration is a physical process where particulates are removed by mechanical means such as particle interception, sedimentation, diffusion, and attachment. The removal of the particulates is driven by the physical properties of the granular media through which the water passes. There are a number of potential unintended consequences related to oxidation filtration, including disposal of residuals from the treatment process, colored water complaints due to inappropriate oxidation, sloughing off of contaminants from the distribution system, altered corrosivity in the distribution system, and formation of disinfection byproducts (DBPs). When aeration is used for oxidation, dissolved carbon dioxide (CO 2 ) is removed from the water resulting in increased ph levels. The increased ph levels may form calcium carbonate scale downstream of the system. If a filter system is located downstream, the scale formation can result in cementing of the filter media. The amount of scale formed depends on the hardness of the water: the harder the water, the more scale is formed. To mitigate this situation, additional treatment can be implemented to remove the hardness, prevent the scale from forming (e.g., chemical sequestration), or reduce the ph prior to any downstream process which may be negatively impacted. Colored water complaints may arise if oxidation filtration is used for manganese removal. Failure to maintain an oxidant residual through the filter, may release manganese accumulated in the filter media or cause the dissolution of manganese solids in the filters, resulting in colored water (pink, yellow, or black/brown water) in the distribution system. Disposal of residuals from the filtration system may be problematic due to the elevated concentrations of suspended solids. The content of the residuals should be considered when selecting a disposal method. Discharging to a receiving stream or wastewater treatment plant may be limited if there are high iron concentrations in the residuals. In waters with high arsenic concentrations, arsenic may be adsorbed to the iron solids resulting in elevated arsenic concentrations that may be regulated by local pretreatment regulations. Another

16 disposal option is to dewater the filtered solids; however, depending on the contents of residuals, the ability to dispose of the solids by local land application may be limited. If arsenic levels are present in high enough concentrations in the residuals, it may be regulated as a hazardous waste. Prior to disposal of any process residuals, the local regulatory agency should be contacted to determine if hazardous waste regulations apply. Addition of a new oxidation process or changing the oxidation/disinfection process may result in changes to the oxidation-reduction potential (ORP) of the distributed water. Reducing the ORP in the distribution system may result in an increase of corrosion and the release of metals, including lead, copper, and iron. This may result in the development of red water in the distribution system. To minimize the potential of the disruptions to the water quality, the use of a corrosion inhibitor, such as orthophosphate, should be considered and consistent secondary disinfection practices and distributed water quality should be maintained. Depending on the type of oxidant used, formation of DBPs may be a concern. For example, the use of chlorine as a oxidant can form DBPs such as, trihalomethanes and haloacetic acids, when it reacts with organic matter in the water. DBPs must be must be monitored at the plant effluent and at agreed upon locations (with the regulatory agency) throughout the distribution system. If DBPs levels exceed compliance levels, additional treatment processes, such as coagulation, adsorption, etc., may need to be implemented at the treatment plant. Approximate capital and operations and maintenance (O&M) costs are provided in Table 1. Table 1. Approximate Costs of Oxidation Filtration Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.50 $1.00 $0.75 $0.50 Annual O&M Cost ($/kgal) 2 $4.50 $1.00 $0.50 $ Costs assume greensand filtration and are similar for dual media (anthracite/sand) and other filter types. Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of oxidation filtration at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $15,000 ($1.50/gal 10,000 gal = $15,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $8,200 ($4.50/kgal 5 kgal/day 365 days/year = $8,212.50). Changes in the ORP may also result in sloughing off of corrosion byproducts in the system piping. These solids may have may elevated concentrations of adsorbed metals that naturally occur in the water, such as arsenic. Increased dissolved oxygen concentrations in the system increases the microbial activity potentially causing regrowth in the system, which may slough off and appear at customers taps. Sloughing off of the solids is typically a concern in relatively aged distribution systems which have higher levels of tuberculation that have resulted from years of operation; therefore, this should be considered when implementing an oxidation filtration process.

17 POST FILTRATION GAC CONTACTORS Granular activated carbon (GAC) is commonly used in drinking water treatment to adsorb synthetic organic chemicals and natural organic compounds that cause taste and odor, color, and can react with chlorine to form disinfection byproducts (DBPs). Adsorption is both the physical and chemical process of accumulating a substance at the interface between liquid and solids phases. GAC is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb. Rapid Mix Flocculation/ Sedimentation Filtration GAC Filter The two most common options for locating a GAC treatment unit in water treatment plants are: (1) post-filter adsorption, where the GAC unit is located after the conventional filtration process (as shown above); and (2) filter adsorbers, in which some or all of the filter media in a granular media filter is replaced with GAC. In post-filter applications, the GAC contactor receives the highest quality water and, thus, has as its only objective the removal of dissolved organic compounds. Backwashing of these adsorbers is usually unnecessary, unless excessive biological growth occurs. This option provides the most flexibility for handling GAC and for designing specific adsorption conditions. The empty bed contact time (EBCT) and the design flow rate define the size of and amount of carbon in a GAC contactor. The EBCT is a measure of the length of time in which water is in contact with the carbon. As the carbon adsorption sites are consumed, breakthrough occurs and the GAC needs to be regenerated or replaced. A longer EBCT can delay breakthrough and reduce the GAC replacement/regeneration frequency. Typical EBCTs for water treatment applications range between 5 to 20 minutes. Shorter EBCTs are likely to require much more frequent replacement or regeneration of the GAC media and the application is likely to become cost prohibitive. GAC is more effective for the removal of DBP precursors than DBPs themselves. As a result, when used for control of DBPs, facilities that utilize pre-chlorination are likely to discontinue that practice. This has the potential to impact removal of dissolved inorganic species, such as iron and manganese. The use of an alternative preoxidant, such as potassium permanganate can help to eliminate this concern. GAC will remove chlorine and chloramines. Therefore, it is necessary to consider the point of primary and secondary disinfectant application when adding GAC to assure the disinfection process is not compromised. Sloughing of bacteria can occur in biologically-active GAC filter adsorbers and post-filter GAC contactors. In systems using free chlorine for both primary and secondary disinfection there should be sufficient free chlorine contact time to inactivate any bacteria dislodged from the GAC media. In systems utilizing chloramines for secondary disinfection, it may be necessary to provide a minimum of 5 minutes of free chlorine contact time prior to ammonia addition. Depending on the economics, facilities may have on-site or off-site regeneration systems or may waste spent carbon and replace it with new. Spent GAC must be in accordance with state and federal laws. On-site regeneration will likely require the facility to acquire air permits. Post-filter GAC contactors are considered secondary filtration under the Long Term 2

18 Enhanced Surface Water Treatment Rule. However, receiving a Cryptosporidium removal credit requires that 100 percent of the flow be treated by the GAC contactors. Approximate capital and O&M costs for post-filter GAC adsorbers are provided in Table 1. Capital costs are based on a 20- minute EBCT and 90-day regeneration frequency and include the addition of GAC contactors, initial load of carbon, associated piping and valves, and instrumentation and controls. O&M costs include spent GAC reactivation, power, replacement parts, and maintenance labor. Table 1. Approximate Costs of GAC Adsorption Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $5.00 $1.50 $1.25 $0.75 $0.40 Annual O&M Cost ($/kgal) 2 $9.00 $5.25 $1.40 $0.30 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of GAC at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $50,000 ($5.00/gal 10,000 gal = $50,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $16,425 ($9.00/kgal 5 kgal/day 365 days/year = $16,425).

19 OZONE AND OZONE RELATED AOPS Ozone (O 3 ) is one of the strongest disinfectants and oxidants available in drinking water treatment. Combinations of ozone and hydrogen peroxide (O 3 /H 2 O 2 ) and ultraviolet light and hydrogen peroxide (UV/H 2 O 2 ) are also being used more frequently as advanced oxidation processes (AOPs). The O 3 /H 2 O 2 and UV/H 2 O 2 processes enhance formation of the hydroxyl radical ( OH) which is a more powerful oxidant than molecular ozone and other oxidants and thus has the capability of oxidizing a variety of organic and inorganic contaminants. Ozone is widely used in drinking water treatment for its oxidation (color, taste and odor, iron and manganese) and disinfection capabilities (Cryptosporidium). AOPs have been demonstrated to be effective for the removal/destruction of compounds not readily oxidized by ozone, or which may require higher than normal ozone doses (e.g., PCE, TCE, atrazine, taste and odor compounds such as MIB and geosmin) and not be cost-effective. AOPs may make oxidation of these contaminants more economical. Ozone can be applied at various points in the treatment train, although it is usually applied prior to coagulation (reduces coagulant demand) or filtration (causes microflocculation which improves filterability). Ozone is typically added to water in a contactor consisting of several enclosed chambers via a diffused bubble system. In the first chamber, water flows downward against rising bubbles while in second chamber, water flows upward. Additional chambers are added to ensure sufficient contact time between ozone and water to achieve the desired treatment objective. configuration allows the utility to obtain disinfection credits for ozonation while achieving the benefit of AOP for destruction of micropollutants. The most common point of application for an UV/H 2 O 2 system is after filtration (lower turbidity, reduced obstruction/shielding of UV light, etc.). Ozone and AOP reactions can produce a number of unregulated disinfection byproducts including aldehydes, ketones, carboxyl acids, epoxides, peroxides, quinine phenols, and brominated organics as well as increased assimilable organic carbon (AOC). If untreated (typically by GAC filter), it may cause biological growth in the distribution system. Ozonation of water containing bromide can lead to the formation of bromate (BrO 3 ), which must be maintained below the regulated 10 µg/l level. Major byproducts formed by O 3 /H 2 O 2 are expected to be similar to those formed by ozonation alone. Studies of UV/H 2 O 2 systems have shown the production of unknown partial oxidation byproducts (not yet regulated). Their impacts to human health are not yet known. Ozone oxidation will also break down many natural organic compounds in to smaller chain molecules which can more easily serve as food for microorganisms. This increase in assimillable organic carbon (AOC) may cause problematic biological regrowth in the distribution system unless removed (typically by biologically active GAC filters). The most efficient operational use of O 3 /H 2 O 2 is to add peroxide into the second chamber of an ozone contactor. This

20 Approximate capital and operations and maintenance (O&M) costs for ozone are provided in Table 1. Capital costs include the addition of an ozone feed system, and contactor (12 minutes), ozone destruction equipment, associated piping and valves, and instrumentation and controls. O&M costs are based on an ozone dose of 7 mg/l and include chemicals, power, replacement parts, and maintenance labor. Costs do not include ph adjustment (which can enhance the oxidation process and can represent a significant O&M expenditure). Table 1. Approximate Costs of Ozone Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $4.00 $1.00 $0.50 $0.25 Annual O&M Cost ($/kgal) 2 $6.50 $0.50 $0.25 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of ozone at a treatment facility with a capacity of 100,000 gpd would be expected to cost approximately $400,000 ($4.00/gal 100,000 gal = $400,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 30,000 gallons (5 kgal) would be approximately $71,175 ($6.50/kgal 30 kgal/day 365 days/year = $71,175).

21 CHLORINE DIOXIDE Chlorine dioxide is a chlorine compound in the +IV oxidation state and is therefore, a powerful oxidant and disinfectant. It is frequently used to improve the removal of iron and manganese, arsenic, color, taste and odor compounds (phenolic, decaying vegetation and algal-related compounds), and inactivate chlorine-resistant microorganisms such as Cryptosporidium. Chlorine dioxide oxidizes natural organic matter (NOM) reducing disinfection byproduct (DBP) precursor concentrations. Chlorine dioxide can also be used as an alternative primary disinfectant to reduce the total chlorine dose. Both may result in a reduction in the formation of chlorinated DBPs, such as trihalomethanes and haloacetic acids. Chlorine dioxide can be applied at several points during treatment: the raw water as a preoxidant, the sedimentation tank, postsedimentation or the filtered water as a primary disinfectant. Chloramine or chlorine must be used for secondary disinfection following chlorine dioxide application. Rapid Mix Flocculation/ Sedimentation ClO 2 Filtration Caustic Storage Pathogen inactivation with chlorine dioxide is much less affected by ph than chlorine. Consequently, chlorine dioxide is a much more effective disinfectant than chlorine at higher ph levels. Iron concentration, manganese concentration, sunlight exposure, and aeration are among the parameters that exert additional chlorine dioxide demand. Greater dose and contact time, as well as increased temperature correlate with greater oxidation and disinfection with chlorine dioxide application. Chlorine dioxide gas is explosive under pressure and must therefore be generated onsite. The generation process can vary depending on the application. Typically, chlorine dioxide is generated from reaction of sodium chlorite (NaClO 2 ) solution with gaseous chlorine (Cl 2 ) or hypochlorous acid (HOCl). Improper generation conditions can lead to the feeding of excess free chlorine at the application point and the potential formation of regulated DBPs. New generators have been developed that replace the solution sodium chlorite with a solid form for minimized byproduct formation; and electrolysis of sodium chlorite has recently been introduced in the U.S. for lowdose applications. Chlorine dioxide yields lower levels of chlorinated byproducts in comparison to free chlorine. However, approximately 70% of the chlorine dioxide applied in water treatment is converted to chlorite (ClO - ) a regulated disinfection byproduct with a maximum contaminant level of 1 mg/l. Chlorate is also a byproduct of chlorine dioxide decay. The maximum recommended sum of chlorine dioxide, chlorite and chlorate in the distribution system should be less than 1.0 mg/l. Approximate capital and operations and maintenance (O&M) costs for a chlorine dioxide system are provided in Table 1. Capital costs include the chlorine dioxide generation and feed system, with associated piping and valves, and instrumentation and controls. O&M costs include chemicals, power, replacement parts, and maintenance labor. Table 1. Approximate Costs of Chlorine Dioxide Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $0.50 $0.05 $0.03 $0.01 Annual O&M Cost ($/kgal) 2 $1.70 $0.15 $0.03 <$ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of chlorine dioxide at a treatment facility with a capacity of 100,000 gpd would be expected to cost approximately $50,000 ($0.50/gal 100,000 gal = $50,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 30,000 gallons (30 kgal) would be approximately $18,615 ($1.70/kgal 30 kgal/day 365 days/year = $15,056).

22 LIME SOFTENING Lime softening is a process that uses chemical precipitation with lime and other chemicals to reduce hardness and remove disinfection byproduct (DBP) precursors in source waters. It can also be used for the removal of arsenic, radionuclides, dissolved organics, color, and microbial contaminants. For these reasons, lime softening is used to comply with many drinking water regulations, including the Long Term 1 and Long Term 2 Surface Water Treatment Rules, Stage 2 Disinfectants and Disinfection Byproducts Rule, Arsenic Rule, Radionuclides Rule, and others. The three most common types of softening processes are conventional lime-soda ash treatment, excess lime treatment, and split treatment. The type of treatment selected is based on the quality of the source water. In each process, chemicals, typically lime and soda ash, are added to precipitate the targeted ions. The precipitates are then removed by conventional processes such as coagulation-flocculation, sedimentation, and filtration. The effectiveness of the lime softening process is dependent on ph, precipitate properties, oxidation state of the contaminant, and specific ultraviolet absorbance value. There are a number of potential unintended consequences related to lime softening including disposal of residual solids from the treatment process, sloughing off of existing corrosion byproducts in the distribution system, and possible leaks in the distribution system. Lime softening produces large quantities of solids that must be dried by mechanical or non-mechanical means. Depending on the quality of the source water, the solids can be land applied, used as a soil conditioner for agricultural lands, or placed in a landfill. Concentrations of naturally-occurring arsenic and radionuclides present in the source waters typically determine the appropriate type of land application. If arsenic or radionuclides are present in high concentrations, the solids may be classified as hazardous or low-level radioactive waste and may not be acceptable for land application. Care should be taken to assure that no naturally-occurring contaminants are present or will not be concentrated in the solids at levels that will be classified as hazardous. In addition to reducing the hardness in finished waters, lime softening may reduce finished water alkalinity, which may, in turn, shift the equilibrium in the distribution system. The change in alkalinity may result in the dissolution or sloughing off of existing scales present in the system. The severity of the impact will vary depending on the age of the distribution system or the type of piping of the distribution system. Sloughing off of scales in older distribution systems or systems with unlined cast iron or galvanized pipes, which are likely to have more tuberculation, may be more prominent than newer distribution systems. Solids may be visible at customers taps until a re-equilibration of the system occurs. The dissolution of the scales and other corrosion byproducts may also expose small leaks in aged and deteriorated

23 piping, particularly in relatively aged homes and distribution systems. Typically, this is not an issue in newer homes. Lime softening typically requires a fairly sizable capital investment and can be costly due to the quantity of chemicals used and disposal costs of large amounts of residuals produced. Approximate capital and operations and maintenance (O&M) costs provided in Table 1 below are for an enhanced lime softening system. Capital costs include the addition of chemical feed equipment O&M costs include chemical costs. Table 1. Approximate Costs of Lime Softening Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $10.00 $5.00 $3.00 $1.50 Annual O&M Cost ($/kgal) 2 $35.00 $6.00 $1.00 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of a package lime softening at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $100,000 ($20.00/gal 10,000 gal = $100,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $64,000 ($35.00/kgal 5 kgal/day 365 days/year = $63,875).

24 NANOFILTRATION / REVERSE OSMOSIS Nanofiltration (NF) and reverse osmosis (RO) are membrane separation technologies that reverse the natural osmotic process by applying a feed pressure which forces water through a membrane against the natural osmotic gradient. This increases the dissolved contaminant concentrations on one side of the membrane. The primary difference between NF and RO is the size of dissolved contaminants that can be removed. NF membranes are typically used for hardness and organics (i.e. DBP precursors) removal. RO membranes are typically used for TDS and monovalent ion removal (e.g., seawater and brackish water desalting, F - and Cl - removal). NF and RO processes include three basic flow streams: the feed, permeate or product, and concentrate or waste streams. A treatment process generally consists of multiple stages, wherein the concentrate from the prior stage becomes the feed for the subsequent stage. The permeate from each stage is blended together for the final product stream. The concentrate from the final stage is usually wasted (Figure 1) NF and RO membrane systems always require some type of pretreatment to prevent membrane fouling. The type of pretreatment required depends on the feed water quality and membrane type. For surface waters, pretreatment may be extensive and include coagulation, sedimentation, ph adjustment, microfiltration, GAC filtration, etc. Residuals generated from NF and RO systems include the concentrate from the membrane processes and the spent cleaning chemicals. Concentrate disposal can be challenging as it is highly regulated by government agencies. Concentrate is typically a relatively high volume, high TDS waste stream and requires a comparatively large body of water for discharge or must be discharged to a wastewater treatment plant or deep well injection. Spent chemical cleaning solutions are generally acidic in nature and require neutralization prior to disposal. NF and RO remove bicarbonate and alkalinity to varying degrees causing depression of the treated water ph, which can impact corrosion control and scale stability in the distribution system. For this reason, ph and/or alkalinity adjustment may be necessary in post-treatment to maintain effective corrosion control downstream of these processes. To prevent corrosion of cement-mortar linings in distribution piping it is recommended that a finished water Langlier Saturation Index (LSI) value of 0.2 or greater be maintained. Values in excess of 0.5 will not cause any corrosion problems by may result in excessive precipitation of calcium carbonate in the distribution system. Similarly, a finished water calcium carbonate precipitation potential (CCPP) value of 4 to 10 will help to prevent dissolution of cementmortar linings, but values in excess of 10 may result in excessive carbonate precipitation. Significant decreases in finished water alkalinity (> 15%), particularly in low alkalinity waters may cause increased corrosion of iron, lead, and copper. The use of an orthophosphate-based corrosion inhibitor (e.g., phosphoric acid or zinc

25 orthophosphate) can help to minimize the potential for increased metals release. Approximate capital and O&M costs are provided in Table 1. Capital costs do not include pre-treatment and post-treatment processes because these are highly depended on the specific source water quality. Capital costs include membranes, feed pumps, associated chemical feed equipment, and electrical and instrumentation. O&M costs include power, replacement parts, membrane replacement, and maintenance labor. Table 1. Approximate Costs of Nanofiltration and Reverse Osmosis Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $8.25 $1.75 $1.00 $1.00 $0.75 Annual O&M Cost ($/kgal) 2 $5.00 $1.50 $0.90 $0.65 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of NF or RO at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $82,500 ($8.25/gal 10,000 gal = $82,500). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $9,125 ($5.00/kgal 5 kgal/day 365 days/year = $9,125).

26 Contaminated Influent ION EXCHANGE/ADSORPTION Ion exchange (IX) and adsorption processes are used to remove dissolved ions and other charged species from water. IX processes are reversible chemical reactions that remove dissolved ions from solution and replace them with other similarly charged ions. Adsorption processes rely on surface charges to adsorb charged ionic species. Most IX and adsorption processes in water treatment operate in a continuous mode. Ion exchange or adsorption occur as water flow (typically in a down-flow mode) through a packed-bed of IX resin or adsorption media. Underdrain Upper Distributor Resin or Adsorption Media Bed Treated Influent In water treatment, the most common IX process is cation exchange softening in which calcium and magnesium are removed. Radium can also be removed from drinking water by cation exchange. Anion exchange processes can be used for the removal of contaminants such as nitrate, fluoride, perchlorate, uranium, selenium, arsenic, sulfate, and natural organic matter (NOM), as well as others. Adsorption processes, such as activated alumina and granular ferric hydroxide, are used to remove arsenic and similar species. Competition for ion exchange or adsorption sites can greatly impact a given system s efficiency in removing contaminants. Generally, ions with higher valence, greater atomic weights and smaller radii are preferred by IX resins and adsorption media. Competing ions lead to a reduction in capacity for the target contaminant. When the capacity of the IX resin is exhausted, it is necessary to regenerate the resin using a saturated solution of the exchange ion (e.g., Na + or Cl - ) Anion exchange processes will generally preferentially remove sulfate over other target contaminants. Removal of sulfate and increased chloride concentrations (as a result of the exchange) can cause an increase in the chloride-to-sulfate ratio, which has been demonstrated to causes increases in lead corrosion in some distribution systems. Strong acid anion exchange resins are generally available in two types: Type I and Type II. Type I resins contain trialkyl ammonium chloride or hydroxide, and Type II contain dialkyl 2-hydroxyethyl ammonium chloride or hydroxide. Type II resins have been demonstrated to release nitrosamines when preceded by chlorination in the treatment process or by an initial rinse following installation or regeneration. The cation exchange functional group includes sodium, which can result in an increase in finished water sodium concentrations. Although there is no maximum contaminant level (MCL) for sodium, USEPA has established a Drinking Water Equivalence Level (i.e., guidance level) for sodium of 20 mg/l. Depending on the TDS and other contaminant concentrations in the spent regenerant, it may be necessary to evaluate the impacts on wastewater treatment plant discharges and National Pollutant Discharge Elimination System (NPDES) requirements. Similarly, disposal of spent media with high concentrations of removed contaminants may require disposal as a hazardous waste. Approximate capital and operations and maintenance (O&M) costs for IX and adsorption are provided in Table 1. Capital costs include the addition of IX or adsorption beds, chemical storage, associated piping and valves, and instrumentation and

27 controls. O&M costs include regenerant/chemicals, power, replacement parts, and maintenance labor. Costs do not include ph adjustment (which can enhance the treatment process and can represent a significant O&M expenditure). Table 1. Approximate Costs of Ion Exchange and Adsorption Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $2.50 $0.75 $0.50 $0.50 $0.50 Annual O&M Cost ($/kgal) 2 $3.00 $1.00 $0.75 $0.50 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of IX at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $25,000 ($2.50/gal 10,000 gal = $25,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $5,475 ($3.00/kgal 5 kgal/day 365 days/year = $5,475).

28 GAC FILTER ADSORBER Granular activated carbon (GAC) is commonly used in drinking water treatment to adsorb synthetic organic chemicals and natural organic compounds that cause taste and odor, color, and can react with chlorine to form disinfection byproducts (DBPs). Adsorption is both the physical and chemical process of accumulating a substance at the interface between liquid and solids phases. GAC is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb. Rapid Mix Flocculation/ Sedimentation Filtration GAC Filter The two most common options for locating a GAC treatment unit in water treatment plants are: (1) post-filter adsorption, where the GAC unit is located after the conventional filtration process (as shown above); and (2) filter adsorbers, in which some or all of the filter media in a granular media filter is replaced with GAC. In the filter adsorber configuration GAC is used for the removal of both dissolved organics and turbidity/suspended solids. Filter adsorbers may also be used for achieving biological stabilization of the treated water. Retrofitting existing high rate granular media filters can significantly reduce capital costs, however, filteradsorbers have shorter filter run times and must be backwashed more frequently than post-filter adsorbers. The empty bed contact time (EBCT) and the design flow rate define the size of and amount of carbon in a GAC contactor. The EBCT is a measure of the length of time in which water is in contact with the carbon. As the carbon adsorption sites become used up, breakthrough occurs and the GAC needs to be regenerated or replaced. A longer EBCT can delay breakthrough and reduce the GAC replacement/regeneration frequency. For filter adsorbers to be effective, an EBCT of at least 5 minutes is generally required. Shorter EBCTs are likely to require much more frequent replacement or regeneration of the GAC media and the application is likely to become cost prohibitive. GAC is more effective for the removal of DBP precursors than DBPs themselves. As a result, when used for control of DBPs, facilities that utilize pre-chlorination are likely to discontinue that practice. This has the potential to impact removal of dissolved inorganic species, such as iron and manganese. The use of an alternative preoxidant, such as potassium permanganate can help to eliminate this concern. GAC will remove chlorine and chloramines. Therefore, it is necessary to consider the point of primary and secondary disinfectant application when adding GAC to assure the disinfection process is not compromised. Sloughing of bacteria can occur in biologically-active GAC filter adsorbers. In systems using free chlorine for both primary and secondary disinfection there should be sufficient free chlorine contact time to inactivate any bacteria dislodged from the GAC media. In systems utilizing chloramines for secondary disinfection, it may be necessary to provide a minimum of 5 minutes of free chlorine contact time prior to ammonia addition. Approximate capital and O&M costs for post-filter GAC adsorbers are provided in Table 1. Capital costs are based on a 20- minute EBCT and 90-day regeneration frequency and include the addition of GAC contactors, initial load of carbon, associated piping and valves, and instrumentation and controls. O&M costs include spent GAC

29 reactivation, power, replacement parts, and maintenance labor. Table 1. Approximate Costs of GAC Adsorption Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $5.00 $1.50 $1.25 $0.75 $0.40 Annual O&M Cost ($/kgal) 2 $9.00 $5.25 $1.40 $0.30 $ Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of GAC at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $50,000 ($5.00/gal 10,000 gal = $50,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $16,425 ($9.00/kgal 5 kgal/day 365 days/year = $16,425).

30 CONVERSION TO CHLORAMINES Chloramines are a family of oxidants formed by the reaction of chlorine and ammonia. In water treatment, chloramines are primarily used as a secondary disinfectant to provide a residual in the distribution system; however, chloramines are occasionally used as a primary disinfectant. Chloramination is often an attractive alternative to chlorine for secondary disinfection because it is more persistent in the distribution system and minimizes the formation of trihalomethanes and haloacetic acids. The ratios at which chlorine and ammonia are fed control the species of chloramines present. Monochloramine (NH 2 Cl) is the preferred species, as it is a more powerful oxidant and is less likely to cause taste and odor problems in the distribution system than dichloramine (NHCl 2 ) and trichloramine (NCl 3 also known as nitrogen tri-chloride). Although a weaker oxidant than chlorine, monochloramine oxidizes precursors of disinfection byproducts, inactivates microorganisms, and controls biofilm. Due to its persistence, chloramines are often more effective in controlling biofilms in distribution system. The effectiveness of chloramination is dependent on dose, chlorine to ammonia ratio, contact time, ph, and temperature. There are a number of potential unintended consequences related to conversion to chloramines for secondary disinfection. The most significant include nitrification and destabilization of existing pipe scales (i.e., corrosion impacts). Nitrification occurs when free ammonia is oxidized by ammonia oxidizing bacteria (AOB) to nitrite (partial nitrification), and nitrite is subsequently oxidized by nitriteoxidizing bacteria (NOB) to nitrate. Some free ammonia is normally present in chloraminated distribution systems as a result of the chloramination process; however, excess free ammonia can be present as a result of 1) poor control of the chlorine to ammonia ratio at the treatment plant and 2) chloramine degradation in the distribution system. Maintaining good control of the chlorine to ammonia feed ratio at the treatment plant is essential to preventing nitrification. A chlorine to ammonia mass ratio of 4.5:1 is generally recommended. Automatic, rather than manual, control of chlorine and ammonia feed systems will also help to reduce the amount of free ammonia entering the distribution system. Research has demonstrated that nitrification is less likely to occur in systems that use chlorine dioxide for oxidation or primary disinfection at the treatment plant due to the toxicity of chlorite to AOB. Systems with high water age (> 14 days), poorly mixed storage facilities, low storage facility volume turnover, and warm water temperatures (> 25 C) are more susceptible to nitrification. Flushing of system dead ends to minimize water age and maintain a chloramine residual can help to reduce the potential for nitrification. Improving volume turnover and mixing in distribution system storage facilities can substantially reduce the potential for nitrification. It is generally recommended that storage volume be turned over at least once every 5 days. In poorly mixed storage facilities, volume turnover may not be sufficient to prevent nitrification due to dead or stagnant zones. Improving mixing to eliminate these areas in the tank will also help to minimize the potential for nitrification and increase distributed water quality from these storage facilities. In poorly buffered waters (i.e., those with low alkalinity), nitrification can also result in increased corrosion. The nitrification process consumes alkalinity (as bicarbonate) and produces carbonic acid. In low alkalinity waters, this has the potential to cause localized depression of ph and

31 increase iron, lead, and copper corrosion. It may also lead to dissolution of cementmortar linings in distribution system piping. Chloramination can also impact existing pipe scale stability due to its lower oxidationreduction potential (ORP) relative to free chlorine. Free chlorine, particularly at higher doses, has a higher ORP than monochloramine which can impact the oxidation state of existing metal pipe scales. At higher ORP values, iron is more likely to be present in ferric forms (Fe 3+ ), which are generally harder and more stable than ferrous iron (Fe 2+ ) species. Similarly, at higher ORP values lead scales are more likely to be present as Pb 4+ species, which are harder and more stable than Pb 2+ scales. Conversion to chloramines may reduce the distributed water ORP causing a shift in existing metallic scale species and result in increases in dissolved metal concentrations. The use of an orthophosphate-based corrosion inhibitor (e.g., phosphoric acid or zinc orthophosphate) changes the metallic (i.e, iron and lead) precipitates on pipe surfaces and can help to minimize the potential for increased metals release as a result of conversion to chloramines. Blending of chloraminated and chlorinated waters in the distribution system is not recommended. Such operation results in a shift in the local chlorine to ammonia ratio and can result in the formation of di- and trichloramine, as well as localized breakpoint chlorination. Any of these consequences is likely to result in increased taste and odor complaints, as well as a reduction in disinfection efficacy. Other potential consequences of chloramination include the production of unregulated disinfection byproducts, including N-nitrosodimethylamine (NDMA) and iodoacids. Chloramination is a low-cost disinfection byproduct control strategy. Approximate capital and operations and maintenance (O&M) costs are provided in Table 1. Capital costs include the addition of an ammonia feed system, with associated piping and valves, and instrumentation and controls. O&M costs include ammonia, power, replacement parts, and maintenance labor. Conversion to chloramines also requires a public education program, may require conversion of booster chlorination or satellite production facilities (i.e., wellfields), and is likely to require some additional level of distribution system O&M. These costs are not included.. Table 1. Approximate Costs of Conversion to Chloramines Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $4.00 $0.50 $0.10 $0.01 <$0.01 Annual O&M Cost ($/kgal) 2 $3.00 $0.20 $0.05 $0.01 <$ Capital costs are based on $ per gallon of treatment plant capacity. For example, conversion to chloramines at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $40,000 ($4/gal 10,000 gal = $40,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $5,475 ($3/kgal 5 kgal/day 365 days/year = $5,475).

32 ph ADJUSTMENT Raising the finished water ph is a common method for reducing corrosion of the distribution system piping and the occurrence of colored water. ph determines the solubility of most pipe materials and the films that form in the pipes from the corrosion byproducts. ph adjustment may also be used as a strategy to reduce the concentrations of certain species of disinfection byproducts (DBPs) in the distribution system. For example, a reduction in ph may reduce trihalomethane (THM) concentrations; however, it may also result in a corresponding increase in haloacetic acid (HAA) concentrations, as discussed later. For these reasons, ph adjustment is primarily used as a corrosion control strategy to comply with the Lead and Copper Rule, though it is occasionally used as an optimization strategy to reduce DBPs. The ph scale ranges from 0 to 14: values less than 7 are considered acidic, 7 is considered neutral, and values higher than 7 are considered basic. Metal surfaces have less of a tendency to dissolve and dissociate at higher ph levels; therefore, ph adjustment can be an effective component in corrosion control of a system. Maintaining a consistent target ph in the distribution system is critical to minimize lead and copper levels at the tap and colored water occurrences. Methods to adjust ph include addition of chemicals, such as sodium hydroxide and soda ash, and the use of aeration and air stripping There are a number of potential unintended consequences related to ph adjustment, including scale formation and plugging of pipes, potential fouling of downstream membrane treatment processes, and altered disinfection efficacy, disinfection byproduct (DBP) precursor removal, corrosivity, and decreased adsorptive capacity of downstream treatment processes. Increasing the ph in finished waters, particularly in hard waters, can result in the formation of calcium carbonate scale downstream of the application point. Scale formation in the distribution system may result in diminished pipe capacities, render distribution valves inoperable, and result in increased pumping costs. Addition of a treatment process to remove the hardness can mitigate the potential scale formation. If the ph is increased prior to the application of the primary disinfectant chlorine, the efficacy of the chlorine may be reduced resulting in the need for additional chlorine to meet primary disinfection requirements (i.e., CT requirements ). Use of a higher chlorine dose may increase DBP formation in the distribution system. In addition, the increased ph may result in a shift in DBP speciation in the distribution system, specifically in the increase of THM concentrations. Prior to implementing a ph adjustment, an evaluation of the water quality should be performed to determine possible impacts to disinfection and DBP formation. It may be necessary to consider an alternative to ph adjustment, improve DBP precursor removal, or change the secondary disinfectant (i.e., convert to chloramines). In systems already using chloramines, a shift in DBP speciation may also occur if the ph is adjusted before ammonia addition during the formation of chloramines. It is advisable that ph is adjusted in small increments in order to reduce negative impacts to a treatment process or increase the possibility of reprecipitation in the distribution system. If large ph adjustments are desired, a

33 filtration system can be installed downstream of the adjustment point; however, there are some considerations if a filtration system is installed. Adjusting the ph prior to existing treatment processes, such as coagulation, adsorption, filtration, etc., may negatively impact the performance of those processes. For example, increases in ph can result in a decrease in coagulation performance and adsorption efficiency. To reduce potential negative impacts to existing treatment systems, it is best to adjust the ph following existing treatment and prior to distribution and in small incremental changes. Treatment systems using nanonfiltration or reverse osmosis systems may also be negatively be impacted if the ph is adjusted upstream of the process, particularly in systems treating water with high iron and/or manganese concentrations. The increased ph may reduce the iron and manganese solubility; therefore, fouling the membranes. The reduced solubility of other foulants may also occur. The use of a pre-filter can help to reduce the potential for fouling. It is advisable to make ph adjustments downstream of any existing membrane treatment system. Approximate capital and operations and maintenance (O&M) costs are provided in Table 1. Table 1. Approximate Costs of ph Adjustment Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.00 $0.20 $0.10 $0.10 Annual O&M Cost ($/kgal) 2 $0.50 $0.20 $0.15 $ Costs assume the use of caustic soda (sodium hydroxide). Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of ph adjustment at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $10,000 ($1.00/gal 10,000 gal = $10,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $900 ($0.50/kgal 5 kgal/day 365 days/year = $912.50).

34 PERMANGANATE ADDITION Permanganate is a strong oxidant used to control taste and odors, oxidize dissolved metals, such as iron and manganese, and control biological growth in treatment plants. Though it is a strong oxidant, and can be used as a disinfectant to inactivate microorganisms, the disinfection capabilities of permanganate are limited. Permanganate can also be used to remove color, control zebra mussels in intake structures and pipelines, oxidize disinfection byproduct (DBP) precursors, and reduce the demand for other disinfectants. The most common type of permanganate used in water treatment is potassium permanganate (KMnO 4 ); though sodium permanganate (NaMnO 4 ) is also used. Typically in water treatment permanganate is applied early in the treatment process; for example, in a preoxidation basin prior to the primary treatment process or at a raw water intake; however, it can also be applied at the rapid mix tank in conjunction with other coagulants or in the clarification process upstream of filters. Potassium permanganate is available as a dry, crystalline solid. Typical feed systems include a dry chemical feeder, storage hopper, collector, solution dissolver tank with mixers, and metering pumps. Effectiveness of permanganate addition is dependent on dose, contact time, ph and temperature. Sodium permanganate is available in liquid form, and is highly acidic. Typical feed systems include bulk storage tanks, transfer pumps and day tanks, and chemical metering pumps. Because of its highly acidic nature, material selection is extremely important, not only for the feed system, but also for downstream equipment and processes. There are a couple of potential unintended consequences related to permanganate addition, including pink water in the distribution system and decreased adsorptive capacity of downstream media. Permanganate addition downstream of the primary treatment process may result in colored water (primarily pink, but black, brown, or yellow are possible) that may become present in the distribution system. Seasonal addition of permanganate prior to filtration or adsorption may also result in colored water in the distribution system. During permanganate addition, a manganese oxide coating may build up in the media and when the addition is discontinued the coating may dissolve, resulting in the colored water. Colored water may also result from the failure to adequately control the permanganate dose (i.e., overdosing). If permanganate is applied prior to filtration or adsorption, it is necessary to maintain a permanganate or other oxidant residual through the media to prevent dissolution of the manganese oxide coating that may form. The adsorptive capacity of a filtration or adsorptive media may be impacted with the addition of permanganate. The manganese dioxide coating formed on the media due to the permanganate addition upstream of the filtration or adsorption system may be beneficial for iron and manganese removal; however, the coating may tie-up adsorption sites and inhibits the adsorptive capacity of the media when other organic or inorganic species are concerned.

35 Approximate capital and operation and maintenance (O&M) costs for a permanganate system are shown in Table 1. Capital costs include the permanganate feed system with associated piping, valves, and storage, and instrumentation and controls. O&M costs include chemicals, power, replacement parts, and labor. Table 1. Approximate Costs of Permanganate Addition Design Flow (mgd) Average Flow (mgd) Capital Cost ($/gal) 1 $1.00 $0.10 $0.05 $0.05 Annual O&M Cost ($/kgal) 2 $0.60 $0.20 $0.15 $ Costs assume the use of potassium permangantate. Sodium permanganate would be more expensive. Capital costs are based on $ per gallon of treatment plant capacity. For example, addition of permanganate at a treatment facility with a capacity of 10,000 gpd would be expected to cost approximately $10,000 ($1.00/gal 10,000 gal = $10,000). 2. Annual O&M costs are based on $ per thousand gallons treated. For example, annual O&M costs for a system with an average daily flow of 5,000 gallons (5 kgal) would be approximately $1,100 ($0.60/kgal 5 kgal/day 365 days/year = $1,095).

36 MAGNETIC ION EXCHANGE Magnetic ion exchange (MIEX ) is a proprietary water treatment process used to remove dissolved ions and charged species from the source water that may be associated with disinfection byproduct (DBP) formation. For that reason, MIEX is most commonly used for compliance with the Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules. MIEX utilizes anion exchange resins to remove the dissolved organic carbon (DOC) from the water by exchanging a chloride ion on the resin surface for the DOC, a significant portion of which is present as complex anions. The resin is located in a fluidized bed ion exchange reactor. The resin is continuously withdrawn from the reactor for regeneration while regenerated resin is placed back into the reactor to provide continuous removal of DOC. Biological growth is minimized in the process by the continual regeneration of the resin with a brine solution. The brine solution used to regenerate the resin typically consists of sodium chloride or other salts. Disposal of the brine solution may be a concern due to the high concentration of chloride and total dissolved solids (TDS). It is important to check with the local sewer/wastewater authority or the appropriate regulatory authority to determine the discharge limitations and to confirm the disposal options of the brine solution. In addition to the removal of DBP precursors, MIEX will remove other anions from the source water, such as sulfate. For every anion removed, chloride ions will be released. Depending on background water quality, increases in chloride and TDS may shift the chloride to sulfate mass ratio, increasing corrosion potential of distribution pipes. Waters with low TDS are likely to be more susceptible to potentially increased corrosion, whereas waters with high TDS concentration may not be as significantly impacted. Courtesy of Orica Watercare There are a number of potential unintended consequences related to MIEX, including increased total dissolved solids concentrations, which can result in corrosion and other problems, and residuals handling issues.

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