The present study is the first comprehensive study of the removal of total bacterial cells from a drinking water supply. Using the direct microscopic count to enumerate the total bacterial population present in raw, settled and filtered water, it was possible to determine bacterial removals by physical processes, such as coagulation, sedimentation and filtration. The 15-month longitudinal study was performed at the Capital City Water Company treatment plant serving Jefferson City, Missouri. The results confirmed earlier survey results indicating that bacterial cell removals by conventional water treatment processes are far lower than turbidity reductions would indicate. Moreover, bacterial removals are significantly impaired when water temperatures are low. Most bacterial removal is accomplished by pretreatment (coagulation and sedimentation). Filtration, as a single unit operation, was found to be ineffective in achieving significant bacterial removals throughout the entire study period. Based on the results, it is evident that the enumeration of the total bacterial population is the most fundamental and basic microbiological measurement that can be made to evaluate water treatment plant performance.Project # G-1027-04 Agreement # 14-08-0001-G-1027-0
