PCBS AND PAHS IN THE MONTREAL URBAN-COMMUNITY (QUEBEC, CANADA) WASTE-WATER TREATMENT-PLANT AND IN THE EFFLUENT PLUME IN THE ST-LAWRENCE-RIVER

Samples of raw and treated wastewater were collected at the Montreal U rban Community (Canada) sewage treatment plant between July and Octobe r 1993 and analysed for PCBs and PAHs. Water samples were also collect ed in the effluent plume in the St Lawrence River during the same peri od. The average concentrations of Sigma 13 PCBs in raw wastewater and treated wastewater were 4.3 and 1.4 ng/l, respectively. For PAHs, aver age concentrations in raw wastewater and treated wastewater were 1.5 a nd 0.4 mu g/l, respectively. The removal rates for PCB congeners and i ndividual PAHs ranged from 33 to 100%. Approximately 1 kg of PCBs and 0.26 tonnes of PAHs were discharged annually by the MUC wastewater tre atment plant to the St Lawrence River. Levels of PCBs and PAHs increas ed significantly at the effluent outfall in the river compared to thos e measured at the upstream site. In the effluent plume, concentrations of PCBs and PAHs reached background levels at approximately 13 and 6 km downstream from the effluent outfall, respectively. (C) 1997 Elsevi er Science Ltd.