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Color, organic matter and sulfate removal from textile effluents by anaerobic and aerobic processes

Amaral, F.M., Kato, M.T., Florêncio, L., Gavazza, S.
Bioresource technology 2014 v.163 pp. 364-369
Daphnia magna, adsorption, biofilters, chemical oxygen demand, color, decolorization, effluents, fabrics, metals, organic matter, sulfates, sulfur, toxicity, upflow anaerobic sludge blanket reactor
An upflow anaerobic sludge blanket (UASB)–submerged aerated biofilter (SAB) system was evaluated to remove color and chemical oxygen demand (COD) from real textile effluent. The system was operated for 335days in three phases (P-1, P-2, P-3) with total hydraulic retention time varying from 21h to 14h. The results showed that high sulfate levels (>300mg SO42−/L) impaired the dye reduction. The best color removal efficiencies of 30% and 96% for the UASB and the reactor system, respectively, were obtained in P-1; the SAB higher efficiency was associated with adsorption. The best COD removal efficiency of 71% for the reactor system was obtained in P-2. Precipitation of some material composed mostly of sulfur (98%) and some metals occurred in the UASB. However, the precipitated sulfur was again oxidized in the SAB. The system also showed an effective toxicity reduction in tests (Daphnia magna) with the treated effluent.