AOC reduction by biologically active filtration

Abstract

Biological treatment was examined for production of biologically stable water, increase disinfectant stability, and reduced formation of disinfectation by-products. Monitoring of assimilable organic carbon (AOC) levels in the effluent of the Swimming River Treatment Plant (SRTP) showed that values 100 ug/L could be related to the occurrence of coliform bacteria in the distribution system. A treatment goal of 100 ug/L was established for biologically active treatment processes. Granular activated carbon (GAC) filters were found to support a larger bacterial population, and thus, provide better biological removal of AOC and total organic carbon (TOC). All biologically active filters showed good performance relative to effluent turbidity levels, and headloss development. Preozonation of raw water increased AOC levels an average of 2.3 fold, and always increased filter effluent AOC levels relative to nonozonated water. Application of free chlorine to GAC filters did not inhibit biological activity. Application of chloramines to GAC filters showed a slight inhibitory effect relative to free chlorine. (Authors)