Biological hydrogen sulfide production in an ethanol-lactate fed fluidized-bed bioreactor

Sulfate-reducing fluidized-bed bioreactor (FBR) fed with ethanol-lactate mixture was operated at 35 °C for 540 days to assess mine wastewater treatment, biological hydrogen sulfide production capacity and acetate oxidation kinetics. During the mine wastewater treatment period with synthetic wastewater, the sulfate reduction rate was 62 mmol SO42- L−1 d−1 and Fe and Zn precipitation rates were 11 mmol Fe L−1 d−1 and 1 mmol Zn L−1 d−1. After this, the hydrogen sulfide production was optimized, resulting in sulfate reduction rate of 100 mmol SO42- L−1 d−1 and H2S production rate of 73.2 mmol H2S L−1 d−1. The limiting step in the H2S production was the rate of acetate oxidation, being 50 mmol acetate L−1 d−1. Therefore, FBR batch assays were designed to determine the acetate oxidation kinetics, and following kinetic parameters were obtained: Km of 63 μmol L−1 and Vmax of 0.76 μmol acetate g VSS−1 min−1. The present study demonstrates high-rate hydrogen sulfide production and high-rate mine wastewater treatment with ethanol and lactate fed fluidized-bed bioreactor.