Comparison of two strategies for assessing ecotoxicological aspects of complex wastewater from a chemical-pharmaceutical plant

Abstract

The potential environmental impact of wastewater from a chemical-pharmaceutical plant was evaluated by two different characterization strategies. The aim of the first strategy was to characterize the complex effluent before and after degradation by activated sludge. Chemical analyses (AOX, EOX, DOC, TOC, BOD, CODCr, N-total, N-NH4, N-NO2, N-NO3, P-total, and P-PO4) were performed on the undegraded and the degraded sample. Ecotoxicological tests were performed on the undegraded sample (acute toxicity, Microtox®, inhibition of respiration of activated sludge, inhibition of nitrification of activated sludge) and on the degraded sample (acute toxicity, Microtox). Moreover, the concentration of potentially bioaccu-mulating substances was determined in the degraded sample. The tests were done according to the STORK Project (characterization of persistent organic compounds in industrial effluents) initiated by the Swedish Environmental Protection Agency. The second characterization strategy was concentrated on single substances in the effluent. The amount of all discharged chemicals was estimated using mass-balance calculations or by chemical analysis of the water phase. Ecotoxicological data for several of the substances were drawn from the reference literature. For those without any ecotoxicological information, a limited set of tests was performed (Microtox, octanol/water partition coefficient, biodegradation). All substances were classified on the basis of environmental effects using acute toxicity, biodegradation, and bioaccumulation criteria. The two different characterization strategies were useful when predicting environmental effects of wastewater from a chemical-pharmaceutical plant. From a practical and economical point of view, a stepwise approach including elements from both of the above strategies is recommended. A chemical-oriented strategy (discharged amount and ecotoxicological data for each compound) may be useful as a primary step for sorting out hazardous water phases from harmless ones. For less defined water phases, an extensive characterization program, including chemical analyses, acute toxicity testing, and ecotoxicological parameters, may give valuable information about environmental risks.