A case study of integration of extensive biomonitoring into the National Pollutant Discharge Elimination System (NPDES) permit of a synthetic organic chemical manufacturing firm in South Carolina to meet the objectives of the Clean Water Act is presented. NPDES monitoring requirements for specific chemicals and quarterly toxicity tests (Mysidopsis bahia) failed to predict severe water quality degradation in a small estuarine receiving stream. This severe disturbance was documented through benthic macroinvertebrate assessments and sediment elutriate bioassays. Additionally, chemical testing revealed the presence of a myriad of toxic, carcinogenic, and other organic chemicals in sediments and oyster tissue in the receiving stream and in outlying public shellfishing areas.

Implementation of monthly oyster-larvae bioassays, annual benthic macroinvertebrate community structure assessments, annual oyster recruitment/settlement assessments, and continuation of the mysid shrimp bioassays as NPDES permit requirements resulted in a comprehensive tool for actual determination of effluent toxicity as well as for guiding the in-facility reduction of toxicity. This comprehensive approach of laboratory toxicity testing of effluents and field monitoring of benthic macroinvertebrate communities provides a measure for assessing chronic or cumulative effects of complex effluents on aquatic communities, especially when those effluents are highly variable due to batch manufacturing processes. This case study suggests that biomonitoring is now developed to a level where it can be implemented to ensure directly that complex toxic effluents are regulated for optimum environmental protection.