| Abstract
| - Low levels of chlorine residual and the trihalomethanechloroform can be released from power plant dischargesand enter natural surface water bodies. Such effluentsmaypose potential human health and ecological risks. Toevaluate these risks, a model was developed and appliedto a time-variable release of these constituents into ariver. The release pattern and dose are typical ofpowerplants. In situ formation of chloroform is alsosimulated.The model is applicable to situations where chloroformisthe dominant trihalomethane. Therefore, the model islimited to water with low background bromide ionconcentrations (approximately 50 μg/L or less). For thescenarioevaluated, predicted total residual chlorine levels,expressedin terms of a hazard quotient for the protection ofaquaticorganisms, are above EPA criteria at locations to withinapproximately 5 km downstream of the discharge; excesslifetime risk to an individual exposed to predicted levelsofchloroform in the river range from 5 × 10-7to above 10-6,a degree of risk that is close to levels of concern toregulatory agencies.
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