Full Description

The Groundwater Replenishment (GWR) System is a joint venture between the OrangeCounty Water District (OCWD) and the Orange County Sanitation District that willeventually treat close to 100 million gallons per day (mgd) of municipal effluent usingmicrofiltration (MF), reverse osmosis (RO), and advanced oxidation (ultraviolet treatmentwith hydrogen peroxide). The GWR System will provide 70-mgd of RO permeate forgroundwater recharge and maintenance of an intrusion barrier to protect the localgroundwater basin from seawater infiltration.OCWD operated Phase 1 of the GWR System between April 2004 and July 2006. Phase1 included reusing a portion of Water Factory-21 (WF-21), a thirty-year old treatmentfacility that consisted of lime clarification and conventional filtration followed by RO. Theexisting pipelines, basins, pumps and RO system were reused while a 6.5-mgd MFsystem was installed and served as the new pretreatment process for the existing 5-mgdRO system. The RO trains were upgraded to thin-film composite membranes. Advancedoxidation was added downstream of the RO process for additional disinfection anddestruction of emerging contaminants. In the summer of 2006, the remaining WF-21facilities used in Phase 1 were decommissioned. The GWR System will consist oftwenty-eight MF units of 3-mgd capacity each and fifteen RO trains of 5-mgd capacityeach, for a total RO production capacity of 70-mgd.The interim Phase 1 facility served as a testing ground that allowed the waterproductions staff to not only optimize its operations and conduct valuable training but toimprove upon the design of the larger 70-mgd GWR System. Staff identified,documented, and corrected multiple issues associated with the MF and RO systems. Inconjunction with the MF manufacturer, a number of issues were resolved, includingsubstandard filtrate quality brought about by membrane integrity, module o-ringdeterioration and hydraulic loading of the filtrate header piping. Improved MF systemperformance was immediately evident in the downstream RO performance. The ROsystem benefited from decreased feed pressures that translated into direct cost-savingsassociated with reduced energy consumption.A variety of cleaning strategies were tested using the 5-mgd RO and included the use ofgeneric and proprietary chemicals. OCWD personnel optimized cleaning proceduresand identified the most efficient and cost-effective method for consistently cleaning themembranes. A new methodology of procuring RO antiscalants (including optimization ofsulfuric acid usage) was also employed. Pilot-scale testing of antiscalant performanceand full-scale application of the lowest cost product resulted in substantial cost-savings. This paper documents the optimizations and improvements made possible by operatingthe interim Phase 1 facility during construction of the GWR System. In addition, thispaper outlines projected savings anticipated for each of the findings. Includes tables, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 20File Size: 1 file , 1.3 MB