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Comparison of Garnet Bead Media Filtration and Multimedia Filtration for Turbidity and Microbial Pathogen Removal
Citation:
Patterson, C. L., R. Haught, R. Sinha, N. Muhammad, R. Krishnan, AND D. Bromley. Comparison of Garnet Bead Media Filtration and Multimedia Filtration for Turbidity and Microbial Pathogen Removal . Presented at AWWA Water Quality and Technology Conference, Cincinnati, OH, November 16 - 20, 2008.
Impact/Purpose:
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Description:
U.S. Environmental Protection Agency’s (EPA’s) National Risk Management Research Laboratory (NRMRL) in Cincinnati, Ohio is evaluating drinking water filtration systems to determine their capability to meet the requirements of the Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) for small communities with less than 10,000 people. This paper presents preliminary results of the tests conducted at the U.S. EPA Test & Evaluation (T&E) Facility in Cincinnati, Ohio to evaluate and compare the effectiveness 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 garnet media that can be fluidized and backwashed. Both systems were challenged with different levels of turbidity and microbiological contaminants including B. subtilis, E. coli and polystyrene latex (PSL) beads (as a surrogate for Cryptosporidium). The results of initial turbidity tests established that the use of fine garnet media ( 33 micron size) in the lead and lag filtration units in the R3f system generated effluent with turbidity levels of approximately 0.5 nephelometric turbidity unit (NTU) from influent feed water with turbidity levels of 5 NTU and 10 NTU. The R3f system was operated at a flow rate of 5 gallons per minute (gpm) without using chemical coagulants. The R3f filtration system performed significantly better than the conventional multimedia filtration system in removing turbidity and microbiological contaminants and surrogates. Although the frequency of backwashing is higher for the R3f system as compared to the multimedia filtration system, the overall water throughput in the R3f system was more than that of the multimedia filtration system. One challenge test was conducted on the R3f filtration system using Cryptosporidium oocysts to verify PSL bead surrogate removal; the results demonstrated equivalent rates of removal.