Abstract

Effluents from two pulp mills in Biobio river basin, Chile were analyzed to evaluate their physico-chemical characteristics and ecotoxicological quality. Toxicity bioassays were performed using P. phosphoreum, D. pulex, C. piger, and S. spinosus. The pulp mills are the ones indicated to provoke the toxic effects on the aquatic organism of different trofic levels. The bioassays, in order of sensitivity, were P. phosphoreum and S. spinosus, followed by D. pulex and C. piger. The importance of considering the ecotoxicological assessment in the quality evaluation of pulp mills effluents is discussed.Effluent samples were collected from two pulp mills located in the Biobio River basin in Chile, and their physicochemical characteristics were determined. The effluents were then used in bioassays involving Photobactereum phosphoreum, Daphnia pulex, Chironomus piger, and Scenedesmus spinosus. Significant differences were noted between the two effluents in terms of temperature, pH, organochlorine compound concentrations, and biodegradable organic material content. In the bioassays, adsorbable organic halide concentration was correlated significantly with toxicity in C. piger, D. pulex, and S. spinosus, but not in P. phosphoreum. Extractable organic halogens were not correlated significantly with toxicity. The less-contaminated effluent provoked toxic effects only in S. spinosus, while the more-contaminated effluent provoked adverse responses in all four species representing different trophic levels.