Microtox™ and Ceriodaphnia dubia toxicity of BKME with powdered activated carbon treatment™

Abstract

This paper compares treatment of bleached kraft pulp mill effluent (BKME) using activated sludge vs. PACT™, with respect to removal of toxicity as measured using two different assays: Microtox™ and Ceriodaphnia dubia. Both activated sludge and PACTTM treatment processes were operated over a range of solids and hydraulic retention times using BKME. Various doses of powdered activated carbon were applied in the PACT™ process. Activated sludge treatment is sufficient to remove nearly all detectable Microtox™ toxicity for bleached kraft pulp mill effluent with initial low to moderate toxicity. Based on the MicrotoxTM toxicity assay, PACT™ was found to slightly improve the toxicity level of highly toxic bleached kraft pulp mill effluent. The chronic Ceriodaphnia dubia toxicity assay was more sensitive than the MicrotoxTM assay in determining toxicity. Significant residual chronic toxicity towards Ceriodaphnia dubia remained in all bleached kraft pulp mill effluents, irrespective of the treatment process. Both activated sludge and PACT™ remove toxicity, but PACT™ effluents are more toxic.

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