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This paper presents experience in recycled water disinfection for Southern California water agencies, including experience in addressing concerns with N-nitrosodimethyamine (NDMA) for indirect potable reuse. The South Orange County Wastewater Authority (SOCWA) is currently designing a new 2.75 million gallons per day (mgd) Advanced Wastewater Treatment (AWT) addition to an existing secondary treatment plant. The new SOCWA AWT will include ultraviolet (UV) disinfection in accordance with the recently revised California UV disinfection guidelines for water reuse. The West Basin Municipal Water District (WBMWD) owns and operates 7.5 mgd of advanced water treatment facilities for indirect potable reuse via injection into Los Angeles County's West Coast Basin Barrier Project. The Orange County Sanitation and Water Districts (OCSD and OCWD, respectively) operate wastewater treatment and reclamation facilities in Fountain Valley, California, including Water Factory 21 (WF- 21), which recycles approximately 5 mgd, also via indirect potable reuse in OCWD's seawater intrusion barrier. OCWD is also designing a major new advanced treatment facility, the Groundwater Replenishment (GWR) Project, as a joint project with OCSD, that will replace WF-21 and produce 70 mgd of high-purity recycled water from secondary effluent now discharged to the Pacific Ocean. This paper presents results of SOCWA, WBMWD and OCWD evaluations of alternatives for meeting the goals of the California Department of Health Services (DHS) with respect to pathogen reduction and concentrations of NDMA in the recycled water, and summarizes design criteria developed for disinfection and NDMA destruction using UV irradiation. While both OCWD/OCSD and WBMWD have also been actively investigating sources of NDMA in the wastewater treatment processes and related mitigation, this paper is limited to results from investigation of UV irradiation for NDMA destruction and disinfection. Includes 4 references, table, figures.

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Edition: Vol. - No. Published: 01/01/2002 Number of Pages: 11File Size: 1 file , 490 KB