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Water quality criteria are one component of the water quality standards which form the foundation of the regulatory programs under the Clean Water Act, and thus are critical in actions such as the evaluation of water body impairment, development of TMDLs, and derivation of permit limits. Water quality criteria also drive decisions made under a variety of other programs, such as those that manage solid and hazardous waste or address threatened and endangered species protection. Despite their great influence and long-term use, few stakeholders fully understand the origin and application, or the potential for misapplication, of water quality criteria. This paper will discuss the context for water quality criteria, derivation procedures (past, present and future), other relevant concepts and tools for water quality assessment, and examples of revisions to water quality criteria that resulted in cost savings for regulated entities.

An overview of the current methodologies used for derivation of ambient water quality criteria (AWQC) for the protection of human health and aquatic life, along with recent changes, will be presented, with particular emphasis on aquatic life methodologies. In addition to chemicalspecific criteria, there are other tools that can be used for water quality-based toxics control. The advantages and disadvantages of biological assessments, toxicity testing, and chemical-specific criteria to achieve aquatic life protection goals will be compared

Future directions for AWQC development and implementation include the potential for incorporating scientific advances in understanding the chemistry, fate, and bioavailability of chemicals. For example, recent research has demonstrated the influence of other water quality characteristics besides hardness on metal toxicity and has led to the development of the Biotic Ligand Model for evaluating metals. Much has been learned from the practice of ecological risk assessment in other arenas (e.g., assessments of risks from pesticides and industrial chemicals, as well as hazardous wastes) that can be used for improving the underlying methodology to derive water quality criteria. A SETAC Pellston workshop convened in 1998 brought together 50 experts from a variety of countries to evaluate the “state of the science” for water quality criteria development, using the principles of ecological risk assessment. Although the methodology developed in the U.S. in 1985 (similar to methods used in other countries) was judged to be basically acceptable, shortcomings were identified relative to criteria derivation, criteria implementation, and cross-media consistency. Improvements in the assessment of bioavailability, the inclusion of factors affecting the biological communities to be protected, the impact of mixtures, and the development of sediment and tissue criteria were discussed. An overview of the recommendations from this workshop will be presented.

Finally, specific examples will be presented that illustrate how changes in the underlying water quality criteria can have a very significant impact upon the costs for treatment or remediation that are incurred by regulated entities. These examples will discuss the approaches used to change water quality standards in two states.

Document Type: Research Article


Publication date: 2003-01-01

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