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The U.S. Environmental Protection Agency (USEPA) regulation has been more and more stringent on disinfection byproducts indrinking water distribution systems since the promulgation of the Stage 1 and Stage 2 DisinfectionByproducts Rules. In the past, at the City of Ft. Lupton, Colorado, total trihalomethanes(TTHM) concentrations in the water distribution system exceeded the maximum contaminationlevel (MCL). Currently, a direct membrane microfiltration process followed by chlorinedisinfection is employed at the Ft. Lupton Water Treatment Plant, which has been ineffective inthe removal of total organic carbon (TOC) (the precursor of disinfection byproducts). Enhancedcoagulation assisted by the membrane ultrafiltration eliminates the need for clarification, whichsignificantly reduces the footprint of the plant. Ultrafiltration is also effective in the removal ofpathogens, bacteria, and viruses. A pilot study was conducted, the objectives of which were toevaluate the efficiency and feasibility of enhanced coagulation, membrane ultrafiltration,granular activated carbon (GAC), and their combinations on TOC removal and examined thelikelihood of the compliance with Stage 2 Disinfection Byproducts Rule (S2DBPR). A pilotplant at the capacity of 4.5 msup3/sup/h was set up and run for over two months. Coagulation with ferricsulfate was optimized in terms of pH and chemical dosing rate. Results show that enhancedcoagulation assisted by membrane ultrafiltration achieved up to 56% TOC removal at pH 5.7 and25 mg/L ferric dose. The membrane flux was stable at 1.5 L/msup2/sup/min for about 1 month withoutthe need for chemical cleaning for recovery. Appending GAC columns to direct membraneultrafiltration achieved 45% TOC removal for GAC20 and 17% TOC removal for GAC10.About 80% of TOC was removed with the combination of enhanced coagulation, membraneultrafiltration, and GAC10 filtration. Simulated Distribution System (SDS)-TTHM analysisindicated that enhanced coagulation and GAC20 will lead to S2DBPR compliance ifimplemented individually. Opinions of Probable Costs (OPC) for different combinations wereestimated and indicated that enhanced coagulation assisted by membrane ultrafiltration was costeffective. Includes 8 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 16File Size: 1 file , 700 KB