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DISINFECTION BY-PRODUCT FORMATION BY ALTERNATIVE DISINFECTANTS AND REMOVAL BY GRANULAR ACTIVATED CARBON
Koffskey, W. E. AND J. Parish. DISINFECTION BY-PRODUCT FORMATION BY ALTERNATIVE DISINFECTANTS AND REMOVAL BY GRANULAR ACTIVATED CARBON. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-93/136 (NTIS 93-222214), 1993.
The effects of the use of the alternative disinfectants on the formation of halogenated disinfection by–products (DBPs) including total organic halide, trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, chloral hydrate, and chloropicrin, were examined along with the ability of granular activated carbon (GAC) to remove these byᰫlproducts and their precursors. Microbiological information was also obtained on the operating system and included heterotropic plate count, total coliform, and assimilable organic carbon (AOC). The ability of the alternative disinfectants to inactivate MS2 coliphage was also examined. One other aspect of the project was to provide sampling sites for health effects research by EPA which will be reported elsewhere.
The operating system was comprised of four parallel pilot column process streams consisting of a 30 min contact chamber followed by a sand column in series with a GAC column having a 20 min empty bed contact time. One of four disinfectants, ozone, chlorine dioxide, chlorine, or chloramines, was applied at the beginning of each process stream. A fifth nondisinfected process stream consisting of only a sand column in series with a GAC column was used as a control.
The lowest levels of halogenated DBPs resulted from the combination of preozonation and postchloramination with annual simulated distribution system averages of 27 µg Cl/L for TOX and 12 µg/L for the sum of 18 DBPs when sand filtration was employed. These respective concentrations were further reduced to 13 µg Cl/L and 7 µg/L with subsequent GAC filtration having a 20 min empty bed contact time. While ozonation produced significant levels of AOC, sand filtration resulted in a 77 percent reduction to 39 µg acetate C–eq/L with subsequent GAC filtration further reducing AOC to 4 µg acetate C–eq/L.