Microbiological pollution in the Canadian upper great lakes connecting channels

The faecal microbiological pollution was investigated in the Upper Great Lakes Connecting Channels by focusing on the near-shore zones of the St. Marys River in Sault Ste. Marie, the St. Clair River in Sarnia and the Detroit River in Windsor (Ontario). Water samples from these rivers and various sources of faecal pollution were analyzed for the indicator organismrecommended by Health and Welfare Canada --Escherichia coli . The observed bacterial counts were characterized by probabilistic distributions and assessed for compliance with the Ontario recreational water quality guideline (100 E. coli/100 mL). The degree and extent of microbiological pollution were related to dry weather sources (malfunctioning sewer systems) and wet weather discharges, particularly combined sewer overflows (CSOs). Excellent water quality was found in Sault Ste. Marie (no CSOs), but poor quality was found in the St. Clair River along a relatively short Sarnia waterfront (5 CSOs) and in a long stretch of the Detroit River in Windsor (25 CSOs). Among the remedial measures, the highest priorities were assigned to both dry and wet weather source controls. Local improvements in microbiological water quality can be achieved by manipulating bacteria transport in rivers - preventing influx of contaminated waters to the areas used for water-based recreation.