Power plants, chlorine, and estuaries

Open Access

Abstract

Results of a year's field investigations at a power plant on upper Narragansett Bay indicated that total residual chlorine at greater than 1.0 ppM was responsible for complete mortality of all pumped phytoplankton and up to 75 percent of the zooplankton. In terms of biological impact, this amounted to approximately 15 tons of primary producer carbon and 1.6 tons of primary consumer carbon from June to December. Biological assay systems using indigenous holo- and meroplankton were designed to model the chlorination patterns of power plants. A matrix of chlorine concentrations and exposure times permitted the generation of response isopleths that were then applied to developing design criteria. This data indicated that certain algal species had a 50 percent reduction in photosynthesis at 0.15 ppM after 10 minutes exposure and complete growth inhibition at 0.3 ppM after 5 minutes exposure. Microzooplanktonic adults showed 50 percent mortality after 5 minute exposures to 2.5 ppM total residual chlorine. Furthermore, chlorinated seawater showed residual toxicity to algae, 100 hrs. postdosing, when no detectable residual chlorine was present. Studies of larval and juvenile fish emphasize that short-term exposure to chlorine levels less than 0.2 ppM will produce a significant biological effect under routine intermittent dosagemore » conditions. Laboratory bioassay data was verified in a field study where the researcher was capable of modifying power plant operations. This study also was used to both develop and verify the use of ATP as a measure of pumped damage to both zooplankton and phytoplankton. The above studies, supplemented by existing data on the toxicity of chlorine to marine organisms, have resulted in a modification of chlorination practices, more stringent effluent guidelines, and revised water quality criteria.« less

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