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Abstract:
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In support of the Environmental Protection Agency's development and finalization of Steam Electric Power Generating Effluent Limitations Guidelines and Standards, Westat calculated the long-term averages, variability factors, and effluent limitations of selected toxic metals (arsenic, mercury, selenium) and harmful pollutants including nutrients (total dissolved solids, nitrate-nitrite as N) based on Flue Gas Desulfurization and gasification wastewater treatment data. Typical effluent datasets consist of serially correlated concentration measurements with a mixture of detected and non-detect data. The limitations are calculated from upper percentiles of the distribution. The modified delta-lognormal (MDL) distribution was used to model the data as a mixture of detected measurements that follow a lognormal distribution and non-detect measurements that occur with a certain probability at one or more sample-specific detection limits. Serial correlation was calculated to adjust the limitations for autocorrelation in data collected over time. These new limits are anticipated to reduce the amount of toxic metals and other pollutants that power plants can discharge by 1.4 billion pounds.
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