TOC REMOVAL IN BIOLOGICAL FILTERS

Laboratory-scale biologically active sand filters were used to evaluat e the effect of natural organic matter (NOM) source and empty bed cont act time (EBCT) on the removal of total organic carbon (TOC) from coag ulated and ozonated NOM solutions. Ozonation at dosages in the range o f 2.0 to 4.0 mg ozone/mg TOC removal in the biofilters ranged from 16 to 33 percent of the biofilter influent concentration. TOC removal was significantly affected by the source of the organic carbon but was in dependent of EBCT in the range of 4 to 20 min. In the context of an en tire water treatment plan, including coagulation and biofiltration, th e contribution with total removals across the entire treatment train. In one biofiltration experiment, however, removal of the biodegradable fraction of TOC was 100 percent, suggesting that biofilters may be ef fective in reducing subsequent regrowth in distribution systems.