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AWWA JAW54062
- Journal AWWA - Spent Filter Backwash Water Contaminants and Treatment Strategies
- Journal Article by American Water Works Association, 05/01/2001
- Publisher: AWWA
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Twenty-five representative water treatment plants were surveyed to comparedifferences in microbial, physical, and chemical water quality of raw waters andspent filter backwash waters (SFBWs). On the basis of the observed Giardia andCryptosporidium levels, it was determined that a recycle ratio of 5-10% would besufficient to minimize the impact of protozoa on ambient raw water. Using thecell culture-polymerase chain reaction method, infectious Cryptosporidium oocystswere observed in raw water and SFBW samples. The presence of particles in theSFBW samples increased the potassium permanganate demand by a factor of 5.5 andthe chlorine dioxide demand by a factor of 4.0. However, the presence ofparticles in SFBWs did not affect the inactivation of Cryptosporidium.Conventional treatment of SFBW with polymers resulted in excellent removal ofturbidity, particles, and microorganisms. A backwashable depth filter can be usedin place of a conventional filter for control of Cryptosporidium in clarifiedSFBW. Includes 29 references, tables, figures.
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