A two-phased approach was used to conduct a site-specific study for cadmium, copper and zinc in the Cuyahoga River in the vicinity of a wastewater treatment plant (WWTP). The objective of the first phase was to determine if the WWTP effluent impacted the aquatic community in the Cuyahoga River. The objective of the second phase was to evaluate the effect of site water on the threshold toxicity of cadmium, copper and zinc and determine site-specific water quality criteria for these metals. The results of the field and laboratory (Ceriodaphnia dubia and fathead minnow chronic toxicity testing of effluent and instream samples) evaluation indicated that the levels of cadmium, copper and zinc in the effluent did not cause toxicity to organisms exposed directly to the effluent, nor did these levels impact the macroinvertabrate and fish communities downstream of the discharge. The results of toxicity tests in site water (both upstream Cuyahoga River water and a mixture of effluent and upstream water) suggested that the Cuyahoga River water and effluent matrices both have substantial assimilative capacities for cadmium and copper.
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