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The City of Minneapolis, Minnesota, has just completed the procurement of the membrane systemfor the second of two low-pressure membrane treatment facilities. The resulting combined capacity of thetwo facilities is 165 MGD. This paper presents the results of the second procurement process and theassociated performance testing results through which the membrane Equipment Contractor for the FridleyMembrane Filtration Plant was selected. The process employed by the Minneapolis Water Works(MWW) and the associated results are of significance to utilities seeking to implement membranefiltration through side-by-side competitive performance testing. The information in this paper willcontribute to the water industry's knowledge base and assist in the piloting and design of futuremembrane filtration facilities.The development of a rigorous membrane performance testing protocol was an important component ofthe MWW process. Participating membrane pilot systems were operated strictly according to thisprotocol to demonstrate treatment efficacy and to establish the basis for comparison. The membranetesting units received the same feed water as the existing granular media filters. Pretreatment of theMississippi River water for filtration involves softening and recarbonation (with powdered activatedcarbon addition) followed by chloramination and ferric chloride coagulation.Unique approaches were adopted in this program to demonstrate pathogen removal capability and allowflexibility in cleaning regimes. The MWW testing program has considerable applicability to otherutilities, particularly those that draw from a surface water source with varying water quality. The keyaspects of the performance testing protocol are briefly presented in this paper. The majority of thediscussion will focus on the performance testing results with particular emphasis on the virus challengetest and applied cleaning philosophies.The test procedure and results for the virus challenge testing are presented. Virus removals of greaterthan 4 log were observed for all pilot units. Included in this discussion are the applicability of particlecounting, turbidity monitoring, and direct integrity tests to assess long-term membrane system integritymonitoring.A comparison of the cleaning regimes, including changes initiated by the Equipment Contractors, arepresented and the associated results discussed. The discussion provides an opportunity to evaluate therelative merits of chlorinated backwashes, performance-based cleaning initiation, and different chemicalcombinations and concentrations. Both chemical washes (frequent, low-dose cleanings) and clean-in-place(CIP) procedures (monthly, high-dose cleanings) were employed by the Equipment Contractors to remove fouling on the membranes. More effective cleans were achieved by adjusting chemicals,chemical concentrations, and cleaning intervals to reflect the changing feed water quality. Includes 3 references, table, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 13File Size: 1 file , 2.8 MB