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Sulfate-rich wastewater treatment using an integrated anaerobic/aerobic biological system

Abstract:

This study evaluated the performance of an integrated anaerobic/aerobic (IAAB) system used for the biological treatment of sulfate-rich wastewater through the reduction of sulfate and the oxidation of sulfide to assess its potential for possible acid mine drainage (AMD) treatment. Separately, an anaerobic sludge was adapted to sulfate-reducing conditions, and an aerobic sludge was activated in a glass column with sucrose as carbon source. Once the sludge activation concluded, the IAAB system, composed of an anaerobic sulfate-reducing reactor (ASRr) and an aerobic sulfide-oxidizing reactor (ASOr), was integrated and operated with a sulfate-rich synthetic solution. The reactor operated with increasing organic (2-4 g COD/L•d) and sulfate (0.4-5.97 g SO2-4/L•d) loading rates and decreasing COD/SO2-4 ratios (5-0.67). During the 43 days of adaptation of the ASRr, a COD/SO2-4 ratio of 1 g/g caused almost a complete displacement of methanogenic activity by sulfate-reducing activity. The removal efficiencies in the IAAB system for COD, sulfate, and produced sulfide were 90%, 60%, and 99%, respectively. By the end of the IAAB system operation, electron flow was mainly directed to sulfidogenic activity, representing 91%. This study demonstrates that a two-step anaerobic/aerobic biological system operating at a high organic loading rate (OLR) can be used for sulfate and organic matter removal from sulfate-rich wastewaters.