Enteric Virus and Indicator Bacteria Levels in a Water Treatment System Modified to Reduce Trihalomethane Production

摘要

A drinking water treatment plant with high concentrations of trihalomethanes (THMs) in its finished water and large numbers of viruses in its source water was located. This plant was used to study the effect of an alteration in the point of chlorination from the first to last step of water treatment on the biological and chemical qualities of its finished water. This alteration caused some reduction in THM production but THM concentrations still exceeded the prescribed limit lf 100 ug/l. No viruses or bacterial indicators were ever isolated from the finished water of the modified plant. Total virus removal by the treatment steps prior to chlorination (coagulation, sedimentation, sand filtration) averaged about 90% while removal of bacterial indicators by these processes averaged between 88 and 98%. Recoveries of viruses and bacterial indicators in the source water were generally negatively correlated.