Effect of the substrate as electron donor during the microbial sulfate reduction and its possible applications in the biological treatment of acid mine drainage

Abstract

The uncontrolled release of acid mine drainage (AMD) characterized by elevated concentrations of dissolved metals, high levels of sulfate ions and low pH values threatens the quality of water resources nearby mining areas worldwide. The development of novel technologies based on the precipitation of metals as metal sulfides catalyzed by sulfate reducing bacteria constitute an important method for the bioremediation ofAMD. The objective ofthis study was to evaluate in batch experiments the efficiency of different organic substrates such as acetate, lactate, ethanol and peptone as electron donors during the generation of biogenic sulfide by different microbial inocula and its possible applications in the bioremediation of AMD. The highest sulfide production activity was obtained with 2.5 g acetate-COD L^-1 as substrate, 4000 mg SO₄^-2 L⁻¹ as electron acceptor and the sediments of an artificial lagoon as bacterial inoculum. The final cumulative sulfide production was 463 mg S^2- L^-1, the maximum specific sulfide production activity was 9 mg S^2- g acetate^-1 d^-1, and the maximum specific sulfate reduction activity was 52 mg SO₄^-2 g acetate^-1 d^-1. In terms of the substrate concentration, a 10-fold increase in the concentration of the electron donor resulted in substrate inhibition significantly decreasing the biogenic sulfide activities. The results of this study indicate that acetate was a highly effective substrate during the microbial sulfate reduction with a potential application in the remediation of acid mine drainage. Moreover, the use of acetate as electron donor favored the sulfate reducing activity through the inhibition ofthe methanogenic activity ofthe microorganisms present in the evaluated microbial inocula.