A novel aerobic sulfate reduction process in landfill mineralized refuse

Abstract

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.