Chemical and Ecotoxicological Monitoring of Discharge Water from a Metal-Finishing Factory

This study investigates the chemical composition and the ecotoxicity of five industrial discharge waters sampled over a three-month period. Twenty-one water parameters and 164 substances were monitored, among them organic and metallic compounds. The results indicated that, on average, 52 substances were found with a high variability, both qualitative and quantitative. Inorganics such as Ca, Na and Cl were present at concentrations close to g/L and metals higher than mg/L. Organics were detected at trace levels (ng/L or mu g/L). The toxicity was assessed by a bioassay based on mobility inhibition of Daphnia magna. The EC50 values were between 3 and 17 % of discharge water, indicating high toxicity. First interpretations suggest that metals, salinity and other unidentified substances, such as commercial organic preparations used in the treatment plant, could be partially responsible for the observed toxicity.