Real textile effluents treatment using coagulation/flocculation followed by electrochemical oxidation process and ecotoxicological assessment

Abstract

As it is well known, the textile industry generates a large amount of wastewater with varied composition that need to be treated. In particular, the Sergipe state, in Brazil, is a region that requires attention due the presence of several local textile industries. In this study, the efficiency of electrochemical oxidation (EO) process applied in the samples of Brazilian textile industry effluents previously treated by physical-chemical process coagulation-flocculation (CF) was evaluated by the reduction in TOC parameter and by the ecotoxicity using Lactuca sativa and Raphidocelis subcapitata bioassays. The optimized experiments achieved for the CF ([Al2(SO4)3]0 = 1.5 mg L−1, pH = 6.0, alkalinity = 0.675 mg L−1, [flocculating agent] = 61 mg L−1, rapid mixing = 100 rpm for 1 min, slow stage = 20–60 rpm for 20 min) a reduction of 20% on TOC. The best results obtained for EO was using the DSA electrode (I = 300 mA) reaching a TOC removal efficiency of 82% after an electrolysis time of 180 min. The ecotoxicity experiments indicated that the proposed treatment (CF + EO, I = 300 mA) was effective to decrease the dissolved pollutants presented in the treated samples. In comparison with raw samples, the treatment achieved a reduction of 52% for IC5072h value using R. subcapitata as bioindicator, and a 98% reduction of LC50 (Lactuca sativa).