City of Oxnard s Advanced Water Purification Facility An Example of Innovative Treatment Application and Design in Maximizing One Southern California Community s Long Term Water Resources Jim Lozier 1, Ufuk Erdal, Imad Feghali, Mary Vorissis, Anthony Emmert and Ken Ortega 1 CH2M HILL 2625 S. Plaza Suite 300 Tempe Arizona, 85282 (480) 377-6218 ABSTRACT The City of Oxnard, a coastal community in southern California, is implementing a strategic water resources program known as the Groundwater Recovery Enhancement and Treatment (GREAT) program. The capstone of the GREAT program is an advanced water purification facility (AWPF) that will utilize a major portion of the secondary effluent from the City s existing water pollution control facility (WPCF) to produce a high quality treated water. The treated water will be used for multiple beneficial uses including irrigation of edible food crops, landscape irrigation, injection into the groundwater basin to form a barrier to seawater intrusion, as well other possible industrial uses to be identified in the future. The AWPF, currently under design by CH2M HILL, will employ a multiple barrier treatment train consisting of microfiltration/ultrafiltration (MF/UF), reverse osmosis (RO), and ultraviolet (UV)-light-based advanced oxidation (AOX) processes to purify the secondary effluent as required to conform to CA Department of Public Health (DPH) Title 22 Recycled Water criteria for groundwater recharge. The AWPF, which will have initial and build-out capacities of 6.25 and 25 mgd, respectively, had to be designed to fit on a 4.3-acre site, with more than one acre dedicated to a combination visitor s center and administration building and other uses not associated with the primary treatment processes. Further, the depth below grade and height of the AWPF s structures (buildings, chemical storage structures) were constrained because of the high groundwater table at the site and the high cost of excavation and dewatering, as well as local codes. To accommodate these various restrictions, an innovative design approach has been developed. This paper summarizes the design constraints and innovative solutions for the design of the AWPF. KEY WORDS Microfiltration, ultrafiltration, reverse osmosis, ultraviolet, advanced oxidation, liquid lime, constructed wetlands, reuse
INTRODUCTION The City of Oxnard (City) has embarked on the Groundwater Recovery Enhancement and Treatment (GREAT) program to make efficient use of their resources. To this end, the City has joined other local water agencies to develop a long-range regional water supply program to address water quality and supply concerns. The GREAT program is a water resources project that combines exchange of water rights with local farmers, wastewater recycling, groundwater injection, and groundwater desalination to use existing local water resources more efficiently. The objectives of the GREAT program are (1) increased reliability of water supply, (2) reduced cost of water supply, (3) improved dependability of water supply in accommodating existing needs and meeting planned growth and associated water demand, and (4) enhanced stewardship of local water supply through recycling and reusing a substantial portion of the wastewater of the region. A major component of the GREAT program is the use of recycled water for multiple beneficial uses including irrigation of edible food crops, landscape irrigation, injection into the groundwater basin to form a barrier to seawater intrusion, and other possible industrial uses. The recycled water for reuse will be generated by the new Advanced Water Purification Facility (AWPF). The source of the recycled water will be the existing City Water Pollution Control Facility (WPCF), which has a capacity of 32.5 million gallons per day (mgd). The AWPF will treat the secondary effluent from the existing WPCF using a proven multiple barrier treatment train consisting of microfiltration/ultrafiltration (MF/UF), reverse osmosis (RO), and ultraviolet (UV)-light-based advanced oxidation (AOX). The high quality effluent produced from these advanced treatment processes will undergo stabilization and disinfection with free chlorine prior to distribution or recharge. The location of the AWPF relative to the southern California region and City of Oxnard is shown in Figure 1. PROJECT COMPONENTS The AWPF project will generate high-purity product water using secondary effluent from the existing WPCF. The AWPF project will be constructed in phases, with product water capacity increments of 6.25 mgd. Capacity of the Initial Phase will be 6.25 mgd. Capacity at the Buildout Phase will be 25 mgd. A gravity line will be constructed to convey secondary effluent from the secondary effluent channel of the WPCF and the inlet structure of the AWPF. Effluent will be intercepted after clarification and prior to disinfection in order to minimize the presence and concentration of contaminants of emerging concern that can be formed during the chlorine based effluent disinfection step. Product water from the AWPF will be used for agricultural and landscape irrigation and for recharge into the aquifer. In addition, product water will be available for local industrial users. Farms in local area will be supplied with the AWPF high-quality product water for agricultural irrigation. The product water will be distributed throughout the City for landscape irrigation using a remodeled sewer trunk line. Groundwater recharge will be conducted by injecting the product water into the ground using newly-constructed injection
Figure 1. Location of Advanced Water Purification Facilities wells located east of the AWPF. The groundwater injection will protect the aquifer from seawater intrusion and provide credit to the City against penalties for over pumping groundwater. All of the end users (agricultural irrigation, landscape irrigation, injection in the aquifer, and industrial) will be served with a common water quality, that which meets the groundwater recharge criteria. In addition to the key objective of producing purified water, the AWPF will have educational, visitor, and research functions. A schematic showing the relation between the WPCF, AWPF and end uses of the AWPF effluent is shown in Figure 2. AWPF Feedwater The City WPCF is a secondary, activated sludge treatment system that is operated as designed for an average solids retention time (SRT) of approximately 2 days to achieve biochemical oxygen demand (BOD) removal only. Low-SRT operation suppresses nitrification, thereby causing a high ammonia concentration in plant effluent. Nonexistent nitrification results in very minor changes in alkalinity during secondary treatment. In addition, low SRT operation prevents oxidation of the slowly biodegradable organics, thereby contributing to relatively high organic concentrations (dissolved organic carbon/total organic carbon [DOC/TOC]) in secondary effluent. The quality of the effluent produced by the WPCF, which will serve as feed to the AWPF, is shown in Table 1. Effluent quality is based on sampling conducted over a 4-month period in 2005 and 2006. The effluent is characterized by high levels of total and dissolved organic
Figure 2. Schematic of Water Pollution Control and Advanced Water Purification Facilities carbon, inorganic ions (sulfate, chloride, sodium and total dissolved solids) and ammonia. Phosphorus levels are only moderate due to the addition of ferric chloride at the headworks of the WPCF for odor control. Ferric addition also aids in the coagulation of colloidal BOD in the raw wastewater. The high levels of TOC and total nitrogen require a high level of removal of these constituents by the RO process in order to meet the California Department of Public Health (CADPH) Title 22 Recycled Water Regulations for groundwater recharge. AWPF Effluent Treatment Goals Effluent from Oxnard AWPF will be used for agricultural and landscape irrigation (during dry seasons) and ground water recharge. In each case, the filtered and disinfected wastewater must meet California s Water Recycling Criteria, Title 22, Division 4, Chapter 3, of the California Code of Regulations unrestricted reuse criteria summarized in Table 2. In addition to the turbidity and disinfection requirements specified in Table 1, the treated wastewater must meet federal and California Drinking Water Standards for inorganic, organic, disinfectants and disinfection by products (DBPs) and CDPH notification (action) level chemicals according to Ground Water Recharge Reuse Criteria (April, 1 2007).
Table 1. Advanced Water Purification Facility Feed Water Quality Constituent (mg/l, unless otherwise stated) Mean Maximum Minimum Dissolved Organic Carbon 13.9 15.7 12.8 Total Organic Carbon 16.6 19.6 14.6 Total Suspended Solids 4.5 8.8 (60) 3 2.4 Total Dissolved Solids 1,750 1,850 1,590 Alkalinity (as CaCO 3 ) 316 328 298 Turbidity (NTU) 3.30 5.20 2.40 Temperature ( o C) 23.0 27.0 1 21.0 1 ph (units) 7.83 7.90 7.70 Boron 1.22 1.29 1.18 Total Hardness (as CaCO3) 644 716 609 Silica 26.7 28.2 25.2 Sodium 339 356 298 Iron (total) (µg/l) 284 415 227 Manganese (total) (µg/l) 92 101 84 Chloride 415 446 362 Sulfate 480 568 422 Ammonia as N 22.2 25.9 19.2 Nitrate as N 1.21 3.20 0.24 Total Nitrogen as N 25.9 31.9 21.5 Total Phosphate as P 1.80 2.50 0.91 The DPH draft requirements 1 include the stipulation for projects that recharge the aquifer with more than 50 percent recycled water that AOX treatment must be provided (subsequent to any RO membrane treatment provided) to achieve at least a 1.2 log 10 reduction of NDMA and 0.5 log 10 reduction of 1,4-dioxane. In March 2002, DPH established an action level for NDMA of 10 ng/l in drinking water. 1 California Department of Health Services (DPH) Recharge Regulations DRAFT April 1, 2007.
Table 2 California Title 22 Requirements for Unrestricted Reuse Turbidity 1 Pathogens Virus Total Coliform 0.2 NTU, 95% of the time within 24 hr period No higher than 0.5 NTU any time A chlorine disinfection process following filtration that provides a CT (The product of combined chlorine residual and modal contact time measured at the same point) value of not less than 450 milligramminutes per liter at all times with a modal contact time of at least 90 minutes, based on peak dry weather design flow; or Minimum 5 log (99.999%) inactivation of MS-2 or Poliovirus 2.2 MPN/100 ml, at 7-day period 23 MPN/100 ml, in 30-day period Does not exceed 240 MPN/100 ml any time 1 Applies filtration processes using membrane technology Additional elements of the draft DPH regulations for groundwater recharge reuse address injection and extraction of the water, nitrogen concentrations ( 10 mg/l as total nitrogen at AWPF effluent), TOC concentrations ( 1 mg/l at AWPF effluent), sampling, and reporting requirements. Of particular interest, during the first year of operation, it is proposed that sampling and analyses include the following: Quarterly: Unregulated chemicals, Priority Toxic Pollutants, chemicals with state notification levels, and other chemicals that DPH has specified including n-nitrosodiethylamine (NDEA) and n-nitrosopyrrolidine (NYPR). Annually: Pharmaceuticals, endocrine disrupting chemicals, and other chemical indicators of municipal wastewater presence as specified by DPH based on a review of the engineering report and the affected groundwater basin(s). Currently, DPH has listed the following for monitoring for information purposes only: Hormones: Ethinyl estradiol, 17-B estradiol, estrone. Industrial endocrine-disrupting chemicals (EDCs): Bisphenol A, nonylphenol and nonylphenol polyethoxylate, octylphenol and octylphenol polyethoxylate, polybrominated diphenyl ethers. Pharmaceuticals and other substances: Acetaminophen, amoxicillin, azithromycin, caffeine, carbamazepine, ciprofloxacin, ethylenediamine tetra-acetic acid (EDTA), gemfibrozil, ibuprofen, iodinated contrast media, lipitor, methadone, morphine, salicylic acid, and triclosan.
Treatment Processes Advanced water treatment facility will include MF/UF pump station, MF/UF, RO, UV disinfection and advanced oxidation (UV/AOX), degasification and water stabilization. Figure 3 shows the process schematic for the advanced water purification facility. Feed Water Chloramination Following diversion, the secondary effluent flowing to the AWPF will be continuously dosed with free chlorine at the WPCF to form a nominal 3 mg/l combined chlorine (chloramines) residual in the AWPF feedwater. Chlorination is required to manage biofouling on both the MF and RO membranes. A combined chlorine residual of 3-4 mg/l will be maintained at the inlet to the MF system for this purpose. Figure 3 Process Schematic for Advanced Water Purification Facility Low Lift Pumping and Screening A low lift pump station will pressurized the chloraminated effluent where it will then flow through 500-um pressure strainers and into a pressure-type microfiltration (MF) system. Pre-Coagulation Bench testing was conducted during the project s conceptual design phase to evaluate the use of in-line coagulation prior to MF in order to reduce TOC loading on the MF and RO
membranes and to decrease the MF fouling potential of the effluent. The testing showed that marginal (<10%) TOC removal could be obtained with ferric chloride at a dose of 30 mg/l (as product). Additionally, ferric addition improved MF filterability to a small degree, increasing projected flux rate by only 10 percent. These improvements were not considered sufficient to justify the space required for ferric bulk storage and feed systems as well as piping necessary to provide sufficient contact to ensure complete ferric chloride hydrolysis and floc formation prior to the MF system. Microfiltration (MF) The MF process uses low-pressure filtration for the removal of particulate and microbial contaminants, including turbidity, Giardia, and Cryptosporidium. MF membranes can produce high-quality RO feed water as measured by turbidity and silt density index (SDI) as well as significantly reduce the bacterial loading to the RO system. RO membrane manufacturers require feed water turbidity and SDI values to be <1 NTU (goal of 0.2 NTU) and <4 (goal of 3 or less), respectively, for sustainable RO system performance. MF/UF filtrate is typically < 0.1 NTU and SDI <3 on secondary effluent and, as such, will easily meet the turbidity and SDI requirements. Not all of the feed water processed by the MF system will be available for RO treatment; some will be used to remove accumulated solids from the membrane surface through regular backwashing and chemically-enhanced backwashing. Backwash water from the MF system will be discharged to a trunk sewer and returned to the WPCF. Waste flows from chemical cleans (CIP) will be ph adjusted and/or dechlorinated prior to discharge to the sewer line. Filtrate from MF system will be conveyed to a pressurized filtrate storage tank that serves as the can for the vertical turbine RO system high pressure pumps. Basic design criteria for the MF system is provided in Table 3. Table 23 Pressurized MF System Design Criteria Parameter Value Design Filtrate Flows (mgd) 7.35 to 7.81 (Initial Phase) 29.4 to 31.2 (Buildout Phase) Flux (gfd) 20-30 Recovery (%) 90 to 95 2 TMP (psi) 3 to 40 CIP Interval (days) 30 (minimum) Membrane Material Polyvinylene difluoride or poly ether sulfone Nominal Pore Size (µm) 0.1 to 0.2 Flow Configuration Outside-in Operating Mode Dead end
Reverse Osmosis (RO) The RO process is a pressure-driven, membrane-separation technique to remove dissolved contaminants (i.e., inorganic and organic solutes) from the MF filtrate. The MF filtrate will first be chemically conditioned with sulfuric acid and scale inhibitor to control the precipitation of sparingly soluble salts as they are concentrated in the RO system. The RO system is designed to convert the MF filtrate into high quality product water (permeate) containing <0.5 mg/l TOC and <100 mg/l total dissolved solids (TDS). RO concentrate, representing 15 percent of the MF filtrate flow, will be will be discharged to the ocean via the WPCF outfall along with neutralized chemical solutions produced from periodic cleaning of the RO membranes. A portion of the concentrate stream will be directed through a demonstration-scale engineered natural treatment system (wetlands) located on the WPCF site. The RO system will be designed for a finished water production capacity of 6.25 mgd for the Initial Phase and 25 mgd for the Buildout Phase. The RO system will contain two trains, each, comprising three stages to allow for a feed water recovery of 80 to 85 percent, where concentrate from the first stage will be applied to a second stage, and the concentrate from the second stage will be applied to a third stage. The combined permeate from each train will serve as the influent to the UV/AOX system. The initial phase of the project will utilize standard 8-inch-diameter by 40-inch-long (8-inch x 40-inch) membrane elements. The ultimate phase will employ the newer, large diameter elements (16-inch x 40-inch ) currently in development by three of the major element manufacturers for both RO system cost savings and to minimize RO train footprint. Ultraviolet Disinfection with Advanced Oxidation (UV/AOX) The UV/AOX process is both a disinfection process and a process for reduction (destruction) of micropollutants, including 1,4-dioxin, NDMA and pharmaceutically active compounds. Hydrogen peroxide will be dosed to the RO permeate upstream of the UV system. Destruction of organic constituents is accomplished when the UV light converts the hydrogen peroxide (H 2 O 2 ) to hydroxyl (free) radicals, resulting in the oxidation of the micropollutants. To meet draft Ground Water Recharge criteria, the UV/AOX system is designed to achieve 1.2-log NDMA and 0.5-log 1,4-dioxane removal. The UV dose to achieve these reductions will greatly exceed that necessary for disinfection of RO product water under the CA DPH Title 22 regulations. Consequently, a high level of protozoan, bacterial and virus pathogen reduction will be provided by the UV/AOX system. Both low pressure high output (LPHO) and medium pressure (MP) systems are proven UV/AOX technologies. The LCC analysis conducted during the project preliminary design phase showed that an LPHO UV/AOX system was far more economical to operate than an MP UV/AOX system because of the impact of high power cost in California.
Post Treatment and Water Stabilization Post-treatment of UV system effluent will be provided to stabilize the effluent prior to conveyance for end use. The post-treatment system will include (1) decarbonator towers and (2) liquid lime injection. UV effluent will be aggressive aggressive with a projected LSI in the range of -3.3 to -2.5 (depending on RO membrane type and degree of RO feed water acidification) and will contain carbon dioxide (CO 2 ) concentrations of up to 50 mg/l. A portion of this CO 2 must be removed to reduce the lime dose needed to increase ph and effluent LSI. Eighty percent of the UV effluent will receive decarbonation. Liquid lime will be dosed to the decarbonated effluent to increase ph and calcium and alkalinity levels and to achieve a minimum LSI of +0.2. The stabilization process is designed to minimize pipeline corrosion during conveyance of the AWPF effluent and to prevent chemical changes when the effluent is recharged (chemical dissolution). Both dry (quick lime and hydrated lime) and liquid-based lime feed systems are available for stabilization. The liquid lime is relatively new in water and wastewater applications. The addition of caustic during liquid lime preparation by manufacturer increases the solubility and stability of the solution. Dry lime systems are complex and operator and maintenance intensive. Bins for dry lime storage are typically 50 to 70 ft tall, which exceeds the maximum height requirements of 35 feet allowable by City codes at the AWPF site. In order to limit the height of the AWPF treatment structures and minimize operator and maintenance requirements associated with lime handling and feed, liquid lime was selected for use at the AWPF. Although more expensive (on a dry weight basis) than quick or hydrated lime, 1iquid lime eliminates the bulky feed system and slaking systems as well as the dust collection system. Liquid lime contains fewer inerts that would increase AWPF effluent turbidity and result in solids deposition in the effluent pump station and pipeline. Liquid lime is dosed directly from a bulk storage tank using metering pumps. To the authors knowledge, this is the first application of liquid lime stabilization of an AWT effluent. Concentrate Treatment In an earlier phase of the GREAT program, the City, with the assistance of CH2M HILL, conducted a pilot-scale project from June 2003 to March 2005 that evaluated the use of a variety of salt marsh plant species to utilize RO concentrate from the Port Hueneme, CA brackish groundwater desalination facility as a feedstock. The objective of the study was to determine if such species could be successfully grown on concentrate such that the concentrate could be utilized in the future as a means to restore diminished coastal salt marsh wetlands in the Oxnard area. The pilot program was a success, identifying multiple plant species that could thrive on the concentrate and providing the following outcomes (Bays et al, 2007): Concentrate can sustain viable native plant communities Removal of nonconservative elements will occur through natural biological and chemical transformation processes and will vary among wetland types Some removal of conservative elements can occur through physical/chemical processes, and removal will vary among wetland types
Discharge is ecologically safe to wetland biota The AWFP demonstration wetland will provide additional information on the ability of an engineered natural treatment system (ENTS) (wetland) to utilize RO concentrate but at a large scale with a more sophisticated, multiple mesocosm system. Treatment of the AWPF RO concentrate represents a greater challenge than that from the brackish groundwater facility due to the much higher concentrations of ammonia, phosphorus and TOC. Site Constraints Drive Process Optimization, Design and Facility Layout The 25-mgd AWPF will be constructed on an existing City parcel that is only 4.65 acres in area. The limited amount of property available required that the facility design minimize the footprint of each treatment process in order to minimize overall facility footprint. Further, the City desired to (1) install a state-of-the art Visitor s Center to facilitate public interaction with and learning about the types of treatment occurring at the AWPF and regarding the GREAT program in general; and (2) locate an operating constructed wetlands on the site in order to demonstrate the ability of natural treatment to remediate and make beneficial use of a portion the RO waste concentrate. The following design aspects played prominently in the facility design in order to minimize space requirements : Use of large-diameter RO units to minimize RO process footprint Stacking of process equipment, if possible Stacking of structural units, such as locating equipment buildings above tanks and wet wells Use of common wall construction with one roof line Use of the turnaround space behind the RO building for an unloading and loading zone for equipment Use of a common electrical room and chemical areas Stacking of structural units was constrained by a maximum building/structure height of 35 feet and the desire not to locate structures and their foundations too far below ground surface because of the high groundwater table (7-15 feet below grade) and the desire to minimize the high cost of groundwater dewatering. A three-dimensional computer rendering of the AWPF showing the location of the primary and residuals treatment processes is shown in Figure 4. The building skins have been omitted from the rendering to show the process units. The administration/visitor s Center has also been omitted for clarity. Figure 5 is the same rendering but with the building skin intact and the administration/visitor s Center also shown. The various components of the ENTS is illustrated in Figure 6.
Figure 4. Location of Primary and Residual Treatment Processes at AWPF (building walls removed) Decarbonation Chemical Storage UV/AOX Wetlands RO MF/UF Low Lift Pumping Figure 5. AWPF Showing Visitor s Center Visitor Center
Figure 6. Engineered Natural Treatment System (Wetlands) for RO Concentrate Major Equipment Procurement Major process equipment for the AWPF, including MF, RO and UV/AOX systems, will be pre-selected by the City. The pre-selection process included three steps. Equipment suppliers were asked to submit three sealed envelopes, each containing different information. The first envelope included qualification information, the second contained technical information and the third bid pricing. The envelopes were opened sequentially starting with the qualifications, followed by the technical and bid pricing. Subsequent envelopes were opened only when a supplier s information from the preceding envelope was deemed acceptable. The bids will be evaluated based on 20-year lifecycle costs.following review of each envelope contents, the equipment suppliers were notified of their review status. Pre-selected equipment will be assigned to the General Contractor. Proof Pilot Testing A proof pilot testing program will be conducted at the WPCF to successfully demonstrate the design criteria and operating parameters proposed by the selected MF and RO system suppliers and, if necessary, to refine site-specific design criteria before the final design of the full-scale facilities. The results of the proof pilot testing program will assist the City of Oxnard achieve the following objectives:
Determine the removal efficiency of total organic carbon (TOC), total nitrogen (TN), total dissolved solids (TDS), and turbidity from the secondary effluent using MF and RO treatment. Characterize reject quality and quantity for residual disposal treatment and permitting. Confirm the effectiveness of the chemical formulations and cleaning protocol of the pilot unit for restoring MF membrane permeability during the clean-in-place (CIP) and chemically enhanced backwash (CEB) procedures, to ensure consistent and repeatable performance over multiple filtration cycles. Allow the City staff to become familiar with operating characteristics of the MF and RO systems SUMMARY The AWPF, in final stages of design by CH2M HILL, will employ a multiple barrier treatment train consisting of microfiltration (MF), reverse osmosis (RO), and ultraviolet (UV)-light-based advanced oxidation (AOX) processes to purify the secondary effluent as required to conform to CA Department of Health Services (DPH) Title 22 Recycled Water criteria for groundwater recharge and to minimize levels of compounds of emerging concern that may be present in the effluent as a maximum safeguard of public health. The product water from this treatment train will be stabilized using partial-flow decarbonation and liquid lime to achieve a non-aggressive for conveyance to users and for recharge. Prior to design, extensive bench testing was conducted to confirm that treatability of the WPCF effluent by the proposed treatment train and to screen the value of additional treatment processes such as pre-coagulation. This testing is reported elsewhere (Chakraborti et al, 2007). The bench testing also permitted pre-selection and procurement of the MF/UF and RO equipment and suppliers prior to pilot testing. The AWPF, which will have initial and build-out capacities of 6.25 and 25 mgd, respectively, had to be designed to fit on a 4.3-acre site, with more than one acre dedicated to a combination visitor s center and administration building and other uses not associated with the primary treatment processes. Further, the depth below grade and height of the AWPF s structures (buildings, chemical storage structures) were constrained because of the high groundwater table at the site and the high cost of excavation and dewatering, as well as local codes. To accommodate these various restrictions, MF will utilize a pressurized module configuration to (i) allow a single pumping step from the gravity effluent line entering the AWPF, through membrane filtration to the RO feed tank and (ii) minimize building height. The RO portion of the AWPF is one of the first advanced reclamation facilities to be designed to utilize large diameter (16 ) RO elements when commercially available and successfully demonstrated, which allows for a minimum footprint for the RO system while reduce equipment and building costs. The UV process will utilize low pressure, high output lamps to minimize footprint. All of the RO permeate will be treated by the H2O2/UV AOX process with a portion of the AOX effluent receiving decarbonation to minimize lime
addition costs while producing a non-corrosive final effluent. In order to limit the height of the AWPF treatment structures and minimize operator and maintenance requirements associated with lime handling and feed, the AWPF will utilize liquid lime rather than dry or slake lime. Direct dosing of liquid lime from a storage tank to the final effluent using a chemical metering pump avoids the maintenance issues associated with dry lime and provides a more stable dosing regime with minimal turbidity increase. An equally-important innovation incorporated into the AWPF design is an ENTS that will treat a portion of the waste concentrate from the RO process. The purpose of the ENTS is to demonstrate that the concentrate can be beneficially reused to sustain the growth of a wetlands type aquatic habitat utilizing aquatic species that are adapted to the local coastal climate. Successful demonstration will then allow concentrate from the AWPF, and possibly other brackish desalination facilities located on the Oxnard Plain, to supply a feed supply for restoration of coastal wetlands. REFERENCES Bays, J., P. Frank and K. Ortega. Oxnard s Membrane Concentrate Wetland Pilot Project. Proceedings of the 22 nd Annual WateReuse Symposium. Tampa, FL. September 9-12, 2007. Chakraborti, R., U. Erdal, J. Lozier, M. Vorissis and T. Maloney. Using Bench-Scale Techniques to Assess Treatment Options for An Advanced Water Purification Facility. Proceedings of the Water Environment Federation Technical Exhibition and Conference. San Diego, CA. October 13-17, 2007.