A novel aerobic sulfate reduction process in landfill mineralized refuse

Highlights: • H₂S from mineralized refuse could be greatly promoted when exposing to O₂. • MFB without SRB has high aerobic sulfate reduction capacity. • Lactate and S₂O₃²⁻ were the preferred electron donor and acceptor for MFB. It is thought that mineralized refuse could be excavated from almost-full landfill sites to provide space for the increasing burden of municipal solid waste. When excavating, however, the H₂S emissions from the mineralized waste need to be considered carefully. In an attempt to understand how H₂S emissions might change during this excavation process, we carried out a series of tests, including exposing anaerobic mineralized refuse to oxygen, isolating and determining possible functional bacteria, and characterizing the electron donors and/or acceptors. The results showed that H₂S would be released when landfill mineralized refuse was exposed to oxygen (O₂), and could reach concentrations of 6 mg m⁻³, which was 3 times the concentrations of H₂S released from anaerobic mineralized refuse. Sulfur-metabolized microorganisms accounted for only 0.5% of the microbial functional bacteria (MFB) derived from the mineralized refuse when exposed to O₂ for 60 days, and SRB were not present. The MFB maintained H₂S production by aerobic sulfate reduction using SO₄²⁻ and S₂O₃²⁻ as electron acceptors, and sulfate-reducing rates of 16% and 55%, respectively, were achieved. Lactate and S₂O₃²⁻ were the preferred electron donor and acceptor, respectively. By enhancing the carbon source and electron transfer, MFB may undergo strong aerobic sulfate reduction even at low abundances of sulfur-metabolized microorganisms.