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2008ii The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality research for its subscribers through a diverse public-private partnership between municipal utilities, corporations, academia, industry, and the federal government. WERF subscribers include municipal and regional water and wastewater utilities, industrial corporations, environmental engineering firms, and others that share a commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life.For more information, contact: Water Environment Research Foundation

The Sanitation Districts of Los Angeles County (Districts) have developed a two-step disinfection process called sequential chlorination. The process applies free chlorine and chloramines in sequence and effectively inactivates viral and bacterial target organisms while minimizing the formation of N-nitrosodimethylamine (NDMA) and trihalomethanes (THMs). To meet California Title 22 requirements as an alternative disinfection technology for "disinfected tertiary recycled water", the Districts embarked on this study and conducted experiments using a pilot-scale channel to determine the free chlorine residual CT values needed to achieve 5-log virus inactivation. Pulse tracer tests were first conducted to demonstrate that the pilot-scale results were applicable to the full-scale system. For the disinfection experiments, the target virus, MS2 coliphage, was seeded into filtered effluent produced from the San Jose Creek East Water Reclamation Plant (SJCEWRP). A total of 114 pilot-scale disinfection tests were conducted over a range of ammonia concentrations, turbidity levels, pH values, and water temperatures. Data from the 99 tests achieving breakpoint chlorination were analyzed and are presented in this paper. For the conditions tested (breakpoint chlorination, modal contact time >4 min), the lowest tested free chlorine residual CT (FCRCT) range of 2 to 3 mg-min/L achieved an average MS2 coliphage inactivation of 5.7-log and a lower 95% confidence level of 5.1-log. Both of these inactivation values exceed the California Title 22 requirement of 5-log virus inactivation for an alternative disinfection technology. Based on the results of this study, the Districts proposed to operate free chlorine disinfection as the first step of sequential chlorination, on filtered effluent at the SJCEWRP under the following conditions:1. Maintain a minimum FCRCT of 9 mg Cl 2 -min/L; 2. Maintain a minimum FCR concentration of 1.0 mg Cl 2 /L; and 3. Maintain a minimum free chlorine modal contact time of 4.0 min. Following a meeting with the California Department of Public Health (CDPH) staff, the Districts expect the CDPH to grant conditional acceptance of sequential chlorination as an alternative for producing disinfected tertiary recycled water at the SJCEWRP before the NPDES and reuse permit for the plant are renewed. WEFTEC 2013

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The objective of this study was to demonstrate the viability and potential application of a high recovery NF/RO integrated treatment system concept. Compared to typically designed and operated high-pressure membrane systems, implementation of the NF/RO Integrated System could reduce the volume of concentrate that needs to be disposed of by approximately one half. The integrated treatment system concept includes a primary NF system and a secondary RO system that is used to treat concentrate produced by the primary NF system. Permeate produced by each system is blended together to achieve an overall recovery greater than 90%.To demonstrate the viability and potential application of the integrated treatment system concept, pilot-scale testing was conducted at the Sanitation Districts of Los Angeles County's San Jose Creek West Water Reclamation Plant using final effluent as feedwater. The final effluent was first treated by a UF system before being fed to the NF/RO integrated system. The system was tested for approximately 2,000 hours at recoveries of 85% for the primary NF system and 54% for the secondary RO system. The operating fluxes during testing were 15 gfd and 10 gfd for the primary NF and secondary RO systems, respectively.The results of this study demonstrate that the high recovery NF/RO integrated treatment system is a viable alternative for indirect potable reuse applications. The system is capable of operation at relatively low overall feed pressure requirements compared to typical high-pressure membrane systems that employ RO membranes. The system achieved a high degree of rejection for some of the constituents that are relevant for indirect potable reuse projects including TOC and select chemicals of emerging concern such as pharmaceuticals, personal care products, and endocrine disrupting compounds. However, relatively poor rejection was achieved for other relevant constituents including nitrate, NDMA, and 1,4-dioxane. Although the integrated system achieves relatively poor rejection for these constituents, application of this system may still be feasible if it is employed as one component of a multi-barrier treatment system. Nitrate removal and control can be achieved biologically upstream of the integrated system. And, as is typically done, a downstream UV/AOP process can be used for removal and control of NDMA and 1,4-dioxane.