2022 Volume 45 Issue 5 Pages 193-205
To maintain a safe drinking water supply, it is essential to understand the occurrence of pathogenic microorganisms in the catchment area of source water. In this study, the previously developed adsorption–elution method of using a negatively charged membrane was optimized in terms of the MgCl2 concentration for adsorption, the H2SO4 volume for acid rinsing, and the NaOH immersion time for elution in order to determine the stable and efficient concentration conditions for viruses in surface water samples. The optimized method was applied to samples collected in Lake Biwa and the Yodogawa River Basin, and pepper mild mottle virus, rotavirus, and norovirus contaminations were investigated. The surface water contamination with feces of human or animal origin was evaluated by measuring Bacteroidales genetic markers specific to humans, pigs, and ruminants, and pharmaceuticals (carbamazepine, sulfamethoxazole, and sulfamonomethoxine) for humans and animals. As a result, the concentrations of viruses and Bacteroidales genetic markers in surface water were found to increase as the Yodogawa River flowed downstream from Lake Biwa. Our observations through the measurements of viruses, bacteria, and pharmaceuticals in surface water demonstrated that the Katsuragawa River was mainly contaminated with feces of human origin, while the Kizugawa River was contaminated with those of animal origin.
