Contamination of rural drinking water wells by fecal origin bacteria - Survey findings

In 1997, over 300 rural drinking water wells throughout Southern Ontario and 148 wells in rural Zimbabwe were tested for bacteriological water quality. Total coliform, fecal coliform and fecal streptococci were enumerated in each sample with standard membrane filtration techniques. Clostridium perfringens was monitored by presence or absence. In Ontario, all of the wells were tested in the spring, when the fields were near saturation, and resampled in late summer. Just under 50% of the wells exceeded the Ontario drinking water objectives (DWO) in spring and summer. On both occasions, approximately 20% of the wells tested positive for Clostridium perfringens, which is an indicator for fecal contamination of animal origin. Zimbabwe wells were sampled during the dry season, June 1997. Ninety-five percent of the wells had bacteria in excess of Ontario DWO, and 59% of the wells tested positive for Clostridium perfringens. The wells in Zimbabwe provided a comparison in soil moisture and type, and there were also differences in well construction and management practices. This study shows that a significant percentage of the bacteria of fecal origin found in rural wells originated from animal manure. Some factors affecting well water quality are discussed.