MICROBIOLOGICAL POLLUTION IN THE CANADIAN UPPER GREAT-LAKES CONNECTING CHANNELS

The faecal microbiological pollution was investigated in the Upper Gre at Lakes Connecting Channels by focusing on the near-shore zones of th e St. Marys River in Sault Ste. Marie, the St Clair River in Sarnia an d the Detroit River in Windsor (Ontario). Water samples from these riv ers and various sources of faecal pollution were analyzed for the indi cator organismrecommended by Health and Welfare Canada Escherichia coi l. The observed bacterial counts were characterized by probabilistic d istributions and assessed for compliance with the Ontario recreational water quality guideline (100 E. coli/100 mt). The degree and extent o f microbiological pollution were related to dry weather sources (malfu nctioning sewer systems) and wet weather discharges, particularly comb ined sewer overflows (CSOs). Excellent water quality was found in Saul t Ste. Marie (no CSOs), but poor quality was found in the St. Clair Ri ver 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 wea ther source controls. Local improvements in microbiological water qual ity can be achieved by manipulating bacteria transport in rivers preve nting influx of contaminated waters to the areas used for water-based recreation. Copyright (C) 1996 IAWQ.