ASSESSING ACUTE TOXICITIES OF PRETREATMENT AND POSTTREATMENT INDUSTRIAL WASTEWATERS WITH HYDRA-ATTENUATA - A COMPARATIVE-STUDY OF ACUTE TOXICITY WITH THE FATHEAD MINNOW, PIMEPHALES-PROMELAS

This study was undertaken to (a) determine wastewater treatment effect iveness using two freshwater organisms, (b) compare acute toxicity res ults from the two species exposed to the wastewaters, and (c) link acu te and potential developmental toxicity of wastewaters in one organism . The acute toxicities of several pretreatment and post-treatment indu strial waste-water samples were evaluated with adult Hydra attenuata ( 92- or 96-h exposure) and fathead minnows (96-h exposure). The acute L C50s agreed closely when results in Hydra attenuata were compared with those from fathead minnow tests. Acute LC50s ranged from 3 to > 100% of sample with hydra, and from 1.0 to > 100% of sample with fathead mi nnows. The results provided strong evidence of treatment effectiveness because toxicity decreased with progressive stages of treatment. Prev iously the Hydra Developmental Toxicity Assay (Hydra Assay) was used a s a prescreen mainly for in vitro assessment of developmental toxicity with pure compounds and to prioritize toxicants according to selectiv e toxicity to the developing embryo (A/D ratio). Recently we modified the assay for testing natural waters and wastewaters; hence, some of t he wastewater samples also were tested for their developmental toxicit y. In this case, the relative selective toxicity (A/D ratio) of these wastewater samples ranged from 0.7 to 2.1, indicating that no sample w as uniquely toxic to the developing embryo, although acute toxicity wa s manifested. Overall, our results indicate the Hydra Assay functions appropriately in assessments of acute and developmental toxicity of in dustrial wastewaters and may be a simple and useful tool in a battery of tests for broader scale detection of environmental hazards.