MONITORING TOXICITY IN 4 WASTEWATERS IN THE BAY-OF-QUINTE, LAKE-ONTARIO

In 1993, as part of the Bay of Quinte Remedial Action plan program, th e toxicity of four wastewater discharges (two from municipal STPs, one from a chemical company, and one from a pulp and paper company) was m onitored in the Bay of Quinte, Lake Ontario. Sequential dilutions of t he best effluents were utilized in algal assays to estimate effluent t oxicity at 100% effluent concentration. The toxicity estimated was exp ressed as mu M/L Cu equivalents. Among the four discharges tested the paper processing effluent was the most toxic at about 100 times the se nsitive level (the concentration above which delicate algal and invert ebrate species would not survive). STP-I wastewater was not toxic. The toxicity of both the chemical company and STP-II wastewaters fluctuat ed in and out of the sensitive zone. Chlorella cells harvested after s ix days exposure to the industrial wastewaters sustained fine structur al damage caused by organic toxicants, while those incubated with muni cipal STP wastewaters exhibited damage due to metals. in the absence o f organic toxicity in STP-II wastewater, a negative correlation betwee n P concentration and metal toxicity was obtained (r(2) = 0.99).