GLEC researchers conducted a TI/RE study to characterize and identify the causative agents of acute and chronic toxicity at industrial and domestic wastewater treatment facilities at one of the U.S. Army's Ammunition Plants. Implementation of the TI/RE was mandated by U.S. EPA Region 6, and GLEC prepared the TI/RE plan for submittal to the agency. GLEC initially conducted static-renewal chronic toxicity tests with Ceriodaphnia dubia and fathead minnows to determine which species was the most sensitive to each final effluent discharge. Upon finding C. dubia to be the most sensitive species to the final effluent toxicity, the characterization/fractionation phase of the program was initiated. Chlorine was the most probable toxicant responsible for the toxicity observed for the domestic wastewater outfall based on the following information 1) the total residual chlorine levels observed in the samples evaluated; 2) the high correlation between the chlorine levels and toxicity; 3) a comparison of the TRC levels in the samples to the final acute and chronic values given in EPA's Ambient Water Quality Criteria document for chlorine; 4) the ability of bench-scale sodium sulfite treatment to remove the chronic toxicity; and 5) the elimination of toxicity associated with the incorporation of the on-site dechlorination treatment system in July 1993.
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