EFFECT OF POINT-OF-USE, ACTIVATED CARBON FILTERS ON THE BACTERIOLOGICAL QUALITY OF RURAL GROUNDWATER SUPPLIES

The water quality of 24 rural, domestic groundwater supplies treated w ith point-of-use, powdered activated carbon (PAC) filters was monitore d to determine how such treatment might impact the bacteriological qua lity of private, residential drinking water supplies, Heterotrophic-pl ate-count (HPC) and total coliform analyses were performed on raw, PAC -treated, and overnight or stagnant (first-draw) PAC-treated water sam ples, Densities of HPC bacteria were elevated by 0.86 and 0.20 orders of magnitude for spring and well water systems, respectively, in PAC-t reated effluents following overnight stagnation compared with levels i n untreated effluents. Densities of HPC bacteria in PAC-treated efflue nts were significantly reduced (P < 0.01) below influent levels, howev er, after the point-of-use device was hushed for 2 min, While PAC sign ificantly reduced the number of coliforms in product waters (P < 0.01) , these indicator organisms were still detected in some effluents. Sea sonal variations were evident in microbial counts from spring but not well water systems, It appears that aside from periods following stagn ant-water use, such as overnight, PAC treatment does not compromise th e bacteriological quality of drinking water obtained from underground sources.