Effects of Conventional Treatment on AOC and BDOC Levels

Abstract

A 12‐month assimilable organic carbon (AOC) survey of 64 conventional water treatment plants was conducted to assess mechanisms affecting effluent AOC levels. The effect of conventional treatment steps (i.e., oxidation, coagulation, filtration, disinfection) on the formation or removal of biodegradable organic matter (BOM) was also investigated at six of the sites. BOM levels were increased or decreased by various factors including the type of filter media, the type of coagulant used, and the level of watershed protection of the plant's source water. Systems that prechlorinated and used anthracite/sand filtration generally had low removal of dissolved organic carbon (DOC) and biodegradable DOC (BDOC) and increases in AOC levels through the treatment process. Systems combining prechlorination and granular activated carbon (GAC) filtration showed increases in AOC in the settled water but removal of AOC through filtration. DOC and BDOC levels were generally reduced by conventional sand/GAC filtration.