BIOTESTING WASTE-WATER FOR HAZARD EVALUATION

Evaluation of the potential hazard of treated water can be performed in two basic ways: chemical identification followed by chemical-by-chemical hazard summation or by means of biotesting the water as if the contaminants were a single compound. Current practice is somewhere in between. For the most part, the use of bioassays is limited to a single test system, and the results are usually interpreted as either positive or negative. That is, binary information is the usual result of a bioassay evaluation. Our work over the past decade has facilitated the development of an alternative approach to interpreting bioassay results. The key element in our approach is the use of relative comparisons. Relative comparisons between responses of a given test system using wastewater and a well-known agent allow a graded response for each different bioassay. By using a battery of different bioassay systems, each with different mechanisms of toxicity. we are able to characterize the composite toxicological response to a wastewater sample with respect to a well-studied ''reference'' chemical. The value of this approach is that, if the use of the reference chemical has acceptable fisk to the majority of the population or at least a known human risk, the wastewater can be evaluated with respect to that factor. We use water chlorination as a ''reference'' material in this report to illustrate the concept.