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AWWA WQTC69482
- Comparison of Garnet Bead Media Filtration and Multimedia Filtration for Turbidity and Microbial Pathogen Removal
- Conference Proceeding by American Water Works Association, 11/01/2008
- Publisher: AWWA
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U.S. Environmental Protection Agency's (USEPA's) National Risk Management ResearchLaboratory (NRMRL) in Cincinnati, Ohio is evaluating drinking water filtration systemsto determine their capability to meet the requirements of the Long-Term 2 EnhancedSurface Water Treatment Rule (LT2ESWTR) for small communities with less than10,000 people. This paper presents the preliminary results of tests conducted at the USEPA Test and Evaluation (T&E) Facility in Cincinnati, Ohio to evaluate and compare theeffectiveness of a radial flow fluidized filter (R3f) versus a conventional multimedia filter(anthracite/sand/garnet/gravel). The R3f system uses either a fine glass bead or a garnetmedia that can be fluidized and backwashed. Both systems were challenged withdifferent levels of turbidity and microbiological contaminants such as B. subtilis, E. coliand polystyrene latex (PSL) beads (as a surrogate for Cryptosporidium). The results ofinitial turbidity tests established that the use of fine garnet media (33 micron size) in thelead and lag filtration units in the R3f system generated effluent with turbidity levels ofapproximately 0.5 nephelometric turbidity unit (NTU) from influent feed water withturbidity levels of 5 NTU and 10 NTU. The R3f system was operated at a flow rate of 5gallons per minute (gpm) without using chemical coagulants. The R3f filtration systemperformed significantly better than the conventional multimedia filtration system inremoving turbidity and microbiological contaminants and surrogates. Although thefrequency of backwashing is higher in the R3f system as compared to the multimediafiltration system, the overall water throughput in the R3f system was more than that ofthe multimedia filtration system. One challenge test was conducted on the R3f filtrationsystem using Cryptosporidium oocysts to verify PSL bead surrogate removal; the resultsdemonstrated equivalent removal. Includes 6 references, tables, figures.
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