URBAN IMPACTS ON MICROBIOLOGICAL POLLUTION OF THE ST-CLAIR RIVER IN SARNIA, ONTARIO

Urban impacts on faecal bacterial pollution of the near-shore zone of the St. Clair River in Sarnia were studied by means of field observati ons and computer modelling. Towards this end, water samples were colle cted at various sources of faecal pollution and at nine sampling stati ons in the river, and analysed for faecal coliform, faecal streptococc i, Escherichia coli, Pseudomonas aeruginosa and coliphage. Probabilist ic distributions of the observed microorganism densities were used to assess the levels of faecal bacteria pollution, describe the impacts o f urban sources on faecal bacteria concentrations in the river, and ma ke inferences about compliance with the recreational water quality gui delines. Relatively high probabilities of guideline violations (p > 30 %, at most sites, in dry weather) indicated the need for remedial meas ures. The screening of such measures was accomplished by preliminary m odelling of indicator bacteria in the receiving waters, using a bacter ia loading model interfaced with a receiving water model.