Evaluation of the toxicity of effluents from pulp bleaching before and after biological degradation

The pulp and paper mill generates high flow rates of wastewater, which is difficult to treat because of its high load of organic matter, organochlorines, lignin and cellulose. Nowadays, the biological treatment is the most widely used by industries. This study aims to evaluate the toxicity removal efficiency of the effluent after biological degradation through ecotoxicological tests. Trials of acute and chronic toxicity studies were performed as the Brazilian Technical Standards Association (ABNT). Two reactors were made of aerobic degradation, one mesophilic (30°C) and other thermophilic (55 °C), also evaluating which is the best system. The results demonstrated that the biological degradation can even eliminate acute toxicity, however, chronic toxicity remains present. The system of mesophilic degradation was more efficient and the alkaline effluent showed greater toxicity before treatment.

biological degradation; toxicity; effluent from pulp bleaching; reactor degradation; ecotoxicology