Interpretation of WET tests for power plants with non-contact cooling water: Methods for estimating net toxicity

Once-through, non-contact cooling water at power plants is frequently discharged back to the fresh or saline waterbody utilized for its intake water. This water is used to cool plant condensers. Little, if any, chemicals are added to this water. If chemicals are added they are either low-levels of biocides or anti-corrosion agents. Interpretation of WET tests for such discharges presents some unique challenges, especially in waters that are the source of the cooling water. The authors present the results of a series of WET tests done on non-contact cooling water for several power plants located on fresh and estuarine waters in the Northeast. In several instances, toxicity was measured in both the source water and the effluent. Initially, this may be interpreted as evidence that the power plant may have added toxicity to the receiving water bodies. Additional tests and analyses of test data, including data for the intake water, demonstrated that these power plants were not adding any significant net toxicity to the receiving waterbodies. They present study design and statistical and WET test methods for comparing intake water toxicity and effluent toxicity to determine whether these power plants were adding any significant toxicity to the effluent and receivingmore » waterbodies.« less