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Ultrafiltration (UF) was selected over other technologies for upgrading an existing 10-million gallon per day (mgd) surface water treatment plant. UF provides a cost-effective approach to comply with new drinking water regulations and meet other operational objectives. The Mission San Jose Water Treatment Plant (MSJWTP) is owned and operated by the Alameda County Water District (ACWD). The plant was constructed in the mid-1970's and uses conventional treatment (i.e., coagulation, clarification, granular media filtration, and chlorination). The plant treats California State Water Project water delivered via the South Bay Aqueduct (SBA). ACWD has plans to upgrade the plant to allow it to comply with upcoming changes in the drinking water regulations and to improve its overall reliability. The plant upgrades will enable the plant to comply with the new Disinfectant/ Disinfection By-Product (D/DBP) Rule and the Enhanced Surface Water Treatment Rule (ESWTR). ACWD also wants to reliably produce a minimum of 8 mgd at all times and 10 mgd in the summer months. Currently, diurnal raw water temperature and pH fluctuations cause settled water turbidity to rise to 10 NTU or more and in turn cause short filter runs. Because of this phenomenon and other facility limitations, the existing plant's processes are not capable of meeting the production targets reliably. Another important water quality issue to be addressed by the upgrades is control of tastes and odors caused by algae in the raw water. This type of problem is common to many conventional water treatment plants. One of the attractions of membrane filtration is that it is not nearly as sensitive to feedwater turbidity as is granular media filtration. Furthermore, UF can achieve complete protozoan removal and significant virus removal, thus minimizing disinfection requirements. This paper discusses the feasibility and cost effectiveness of ultrafiltration (UF) membrane processes for replacing existing granular media filters. The decision whether to proceed with UF system installation for upgrade of ACWD's MSJWTP hinged on the confirmation that this technology met the treated water quality goals established by the District and proved less expensive on a net present value basis than conventional treatment with intermediate ozonation. Based upon conclusions of initial feasibility studies, ultrafiltration was selected over microfiltration for further evaluation in the continuation of the MSJWTP preliminary design. A UF membrane pilot study was conducted as a part of the preliminary design evaluation effort. The six-month testing period allowed time for comparative evaluation of three UF pilot units on raw and pilot-clarified waters from the South Bay. The following objectives were established for the pilot study: demonstrate and compare the operational performance and removal capabilities of systems from three different ultrafiltration (UF) membrane suppliers; evaluate the operational performance of UF membrane pilot systems and the UF permeate water quality of the UF processes under different feedwater conditions (e.g., raw feedwater vs. clarified feedwater) and confirm the best process sequence; determine membrane performance criteria appropriate for inclusion in a pre-qualification or pre-purchase bid package; estimate membrane facility capital and O and,achieve overall project cost savings through judicious investment in pilot testing. Includes tables, figure.

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Edition: Vol. - No. Published: 11/01/2002 Number of Pages: 16File Size: 1 file , 380 KB