The U.S. Army is currently conducting research to develop the data base required to establish water quality criteria for wastewater discharged from 2, 4, 6-trinitrotoluene (TNT) production facilities. Because over 30 munitions-related compounds are involved, a traditional compound-by-compound approach to the toxicological evaluation of this complex wastewater was considered both technically unacceptable and economically prohibitive. An alternate approach was developed that placed research emphasis on the toxicological evaluation of a representative wastewater mixture. The initial task, therefore, was to conduct a detailed wastewater chemical characterization study over a period of several months. Wastewater constituents were identified and quantified, and, through the use of statistical procedures, a mixture representative of the actual wastewater was defined. Only 22 of the compounds identified in the actual wastewater were detected consistently above the parts-per-billion detection limit. These were included in the mixture designated for detailed toxicological testing. To identify possible trace constituents with extraordinary toxicological properties, all the identified compounds received screening-type toxicological testing. In addition, in attempting to relate the toxic properties of the mixture to its components, detailed toxicological studies are continuing to be conducted on selected components of the mixture, that is, on major components and on extremely toxic minor components.

We believe that this combined approach of single compound and mixture testing provides both an economical and scientifically acceptable approach to the development of water quality criteria for complex industrial wastewaters that remain relatively constant over time. In this approach the “no-effect” level determined from chronic toxicity studies with the mixture will be the principal basis for the water quality criteria. This will be supplemented with the identification of components with extraordinary toxicological properties and the definition of the dose-response relationship for the major toxic compounds in the mixture.