Regulatory implications of using constructed wetlands to treat selenium-laden wastewater

The practice of using constructed wetlands to treat selenium-laden wastewater is gaining popularity in the United States and elsewhere. However, proponents of treatment wetlands often overlook important ecological liabilities and regulatory implications when developing new methods and applications. Their research studies typically seek to answer a basic performance question--are treatment wetlands effective in improving water quality--rather than answering an implicit safety question-are they hazardous to wildlife. Nevertheless, wetland owners are responsible for both the operational performance of treatment wetlands and the health of animals that use them. This is true even if wetlands were not created with the intent of providing wildlife habitat; the owner is still legally responsible for toxic hazards. If poisoning of fish and wildlife occurs, the owner can be prosecuted under a variety of federal and state laws, for example, the Migratory Bird Treaty Act and the Endangered Species Act. In considering this type of treatment technology it is important to document the selenium content of the wastewater, understand how it cycles and accumulates in the environment, and evaluate the threat it may pose to fish and wildlife before deciding whether or not to proceed with construction. Many of the potential hazards may not be obvious to project planners, particularly if there is no expressed intention for the wetland to provide wildlife habitat. Ecological risk assessment provides an approach to characterizing proposed treatment wetlands with respect to wildlife use, selenium contamination, and possible biological impacts. Proper application of this approach can reveal potential problems and the associated liabilities, and form the basis for selection of an environmentally sound treatment option.