DAF TREATMENT OF A RESERVOIR WATER-SUPPLY - COMPARISON WITH IN-LINE DIRECT-FILTRATION AND CONTROL OF ORGANIC-MATTER

The goal of this paper is to compare the performance of an in-line dir ect filtration (no flocculation) process with a dissolved air flotatio n (DAF) and filtration process for drinking water treatment. Both proc esses were studied at the pilot scale and included biologically active dual media (GAC/sand) rapid filters. Specific attention is given to t he fate of organic matter. Organic matter was analyzed by measurements of dissolved organic carbon (DOC), assimilable organic carbon (AOC), disinfection by-product formation potential (DBPFP) and ultraviolet ab sorbance at 254 mt (UV254). In general, flotation removed a large frac tion of organic matter with additional removal provided by biologicall y active filters. Most of the work occurred with ozonation of the raw water (pre-ozone). Ozone increased the biologically assimilable fracti on of the water; filtration decreased this fraction to acceptable leve ls. Overall, effects of ozone on other organics are relatively small.