Characterization of a Marine Microbial Community Used for Enhanced Sulfate Reduction and Copper Precipitation in a Two-Step Process

Marine microorganisms that are obtained from hydrothermal vent sediments present a great metabolic potential for applications in environmental biotechnology. However, the work done regarding their applications in engineered systems is still scarce. Hence, in this work, the sulfate reduction process carried out by a marine microbial community in an upflow anaerobic sludge blanket (UASB) reactor was investigated for 190 days under sequential batch mode. The effects of 1000 to 5500 mg L⁻¹ of SO₄ ⁻² and the chemical oxygen demand (COD)/SO₄ ⁻² ratio were studied along with a kinetic characterization with lactate as the electron donor. Also, the feasibility of using the sulfide produced in the UASB for copper precipitation in a second column was studied under continuous mode. The system presented here is an alternative to sulfidogenesis, particularly when it is necessary to avoid toxicity to sulfide and competition with methanogens. The bioreactor performed better with relatively low concentrations of sulfate (up to 1100 mg L⁻¹) and COD/SO₄ ⁻² ratios between 1.4 and 3.6. Under the continuous regime, the biogenic sulfide was sufficient to precipitate copper at a removal rate of 234 mg L⁻¹ day⁻¹. Finally, the identification of the microorganisms in the sludge was carried out; some genera of microorganisms identified were Desulfitobacterium and Clostridium.