Site-Specific Evaluation of Power Plant Chlorination

The literature on chlorine toxicity to aquatic organisms is critically reviewed regarding methodology. Extant toxicity data for marine and freshwater organisms are summarized using log concentration versus log time plots of median tolerance (50 percent) levels. Acute and chronic toxicity thresholds are approximated by enclosing these data points and then shifting the resultant lines. The chronic toxicity threshold for fresh water is 0.0015 mg/l, while that for salt water is 0.02 mg/l. A site-specific procedure for evaluating chlorination schemes at a power plant is proposed based on comparison of dose-times expected in its discharge plume with the above toxicity thresholds. Dose-times higher than the threshold are considered to yield mortality while those below it are not toxic. An analysis of a hypothetical marine-based power plant is presented.