Ecological basis for regulating aquatic emissions from the power industry: the case with selenium.

Selenium can have severe ecological impacts on aquatic ecosystems even when waterborne concentrations are in the low microgram per liter (ppb) range. Episodes of environmental contamination have occurred that clearly illustrate the potential toxicity of this trace element to aquatic organisms. Wastes and effluents produced by the power industry are highly concentrated sources of selenium and constitute hazardous wastes when introduced into aquatic ecosystems. The continued use of a wet-basin system of coal-ash disposal at power plants is only feasible if several environmental variables are considered along with models of trace element cycling and accumulation, and pretreatment of effluents. Other power industry operations, such as coal gasification and liquifaction, must include provisions for treating effluents as an integral part of construction design. The ecological data base indicates that new, rigorous water quality criteria for selenium are needed; criteria presently proposed by EPA and others would not protect freshwater life if adopted as standards by regulatory agencies. This data base has been utilized by the State of North Carolina to develop sound, defensible environmental standards for selenium in surface waters. Ecological information can be used nationwide to establish reasonable and prudent regulations governing selenium-laden effluents from the power industry.