Vulnerability of a fractured dolostone aquifer to emerging sewage-derived contaminants and their use as indicators of virus contamination
During an 8 month sampling campaign, 22 wells (11 private, 8 municipal, and 3 monitoring wells) completed in the fractured Silurian dolostone aquifers of southern Wellington County, Ontario, Canada were sampled for enteric viruses, fecal bacteria, artificial sweeteners, pharmaceuticals, and other common constituents of human and animal sewage. The vulnerability of fractured bedrock aquifers to sewage-derived contaminants was highlighted when 91% of the sampling wells exhibited at least one of the 49 sewage derived contaminants analyzed in this investigation. Low concentrations of viruses were found in 45% of the wells but each of these wells only exhibited viruses on one of the monthly sampling events. Current regulations in Canada and the United States require the monitoring of total coliforms and E. coli to determine the presence of a sewage influence in drinking water supplies, but statistical calculations of positive and negative predictive values, specificity, and sensitivity showed that the artificial sweetener acesulfame may act as a more effective tracer of sewage-derived contamination and the combination of ibuprofen and total coliforms may be able to indicate up to 70% of virus occurrences in southern Wellington County’s fractured bedrock aquifers. While the results may suggest that private well owners consuming untreated groundwater are at risk of acute gastrointestinal illness, the scope of the current study does not permit an assessment with regards to the risk of consuming water from municipal supplies.