BIOTESTING WASTE-WATER FOR HAZARD EVALUATION

Evaluation of the potential hazard of treated water can be performed i n two basic ways: chemical identification followed by chemical-by-chem ical hazard summation or by means of biotesting the water as if the co ntaminants were a single compound. Current practice is somewhere in be tween. For the most part, the use of bioassays is limited to a single test system, and the results are usually interpreted as either positiv e or negative. That is, binary information is the usual result of a bi oassay evaluation. Our work over the past decade has facilitated the d evelopment 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 wa stewater and a well-known agent allow a graded response for each diffe rent 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 i s that, if the use of the reference chemical has acceptable fisk to th e majority of the population or at least a known human risk, the waste water can be evaluated with respect to that factor. We use water chlor ination as a ''reference'' material in this report to illustrate the c oncept.