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In order to meet the Stage 1 and future Stage 2 Disinfectant and Disinfection ByproductsRules, the Cobb County-Marietta Water Authority has completed an intensive pilot-scaleevaluation of advanced treatment technologies for disinfection byproduct (DBP)precursor removal at the 72-million-gallons-per-day (mgd) Wyckoff water treatmentplant (WTP). The authority had observed elevated DBP levels in the distribution system,and due to the fact that several consecutive systems purchase water from multiple sourcesand areas with extended hydraulic residence time, simple solutions such as decreasingchlorine dose or switching to chloramines were not options.The study was conducted over a 12-month period by the authority and its consultant,CDM, utilizing a two-train pilot-scale treatment plant. One train was used to simulateexisting rapid mixing, flocculation, sedimentation, and filtration treatment processes toprovide a baseline comparison, while the second train was used to evaluate the effect ofadding various DBP precursor reduction technologies to the existing Wyckoff WTPtreatment process train. Technologies evaluated in the study included pre-chlorinedioxide in lieu of prechlorination, pre- and intermediate-ozone/biofiltration, magneticallyenhanced ion exchange (MIEX), and post-filter nanofiltration.Results of the study indicated the ability of the Wyckoff plant to significantly lower DBPlevels to meet Stage 1 requirements by switching to chlorine dioxide as a pre-oxidant inlieu of prechlorination. Ozone/biofiltration did not have an incremental difference in theresults for DBP precursor removal compared to pre-chlorine dioxide. Both pretreatmentwith MIEX and post-filter nanofiltration provided significant reduction in DBPprecursors, allowing these technologies to be considered for future implementation tomeet Stage 2 DBP requirements. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 13File Size: 1 file , 360 KB