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Dissolved and particulate forms of copper are common trace contaminants in storm runoff and wastewater. In the dissolved state, copper appears in various forms, ranging from the cupric ion to numerous organic-inorganic complexes. The ionic form of copper is toxic at very low concentrations, while complexed copper is basically nontoxic. Regulatory agencies have long known about this "Jekyll and Hyde" behavior, but the standard permitting approach has been to assume that all dissolved copper is present in the most toxic form, which is rarely accurate because the ionic form is highly reactive, readily forming nontoxic complexes.
Laboratory-derived numerical water quality criteria for copper, developed by the U.S. Environmental Protection Agency (EPA) in 1984 and updated in 1993, assume that the toxic form of dissolved copper exists in biologically treated effluents when, in fact, it does not. This causes erroneous permits to be issued, municipal resources to be misdirected, and industrial facilities to be adversely affected.
EPA's copper criteria should not be applied directly to municipal effluents for the following reasons:
The database used to derive existing criteria did not take into account copper detoxification by constituents commonly present in biological waste treatment systems.
Laboratory studies, field surveys, and water effects ratio procedures conducted by regulatory authorities and independent researchers since 1976 verify that copper rapidly binds with organic and inorganic matter during biological waste treatment, making it unavailable to interact biologically (nonbioavailable) and thus nontoxic to aquatic life.
All EPA and state agency field studies confirm that copper in biologically treated effluents is not toxic to Daphnia, the sensitive species used to establish the federal copper criteria.
These studies demonstrate that biologically treated effluents eliminate copper toxicity with significant additional complexing capability in reserve. Copper typically discharged (40 to 200 ug/L) by publicly owned treatment works (POTWs) should pose no threat to aquatic species. Laboratory research on the detoxifying effects of organic and inorganic matter on copper (including total organic carbon; particulate matter; and humic, fulvic, and amino acids) explains why scientific field studies consistently show that copper in biologically treated effluents is not expected to be toxic to aquatic life.
Impacts of Outdated Science
POTWs faced with inappropriate copper limits typically pass these limits on to the facilities' industrial users or modify potable water...