Characterizing the biotransformation of sulfur-containing wastes in simulated landfill reactors

摘要

Landfills that accept municipal solid waste (MSW) in the U.S. may also accept a number of sulfur-containing wastes including residues from coal or MSW combustion, and construction and demolition (C&D) waste. Under anaerobic conditions that dominate landfills, microbially mediated processes can convert sulfate to hydrogen sulfide (H_2S). The presence of H_2S in landfill gas is problematic for several reasons including its low odor threshold, human toxicity, and corrosive nature. The objective of this study was to develop and demonstrate a laboratory-scale reactor method to measure the H_2S production potential of a range of sulfur-containing wastes. The H_2S production potential was measured in 8-L reactors that were filled with a mixture of the target waste, newsprint as a source of organic carbon required for microbial sulfate reduction, and leachate from decomposed residential MSW as an inoculum. Reactors were operated with and without N_2 sparging through the reactors, which was designed to reduce H_2S accumulation and toxicity. Both H_2S and CH_4 yields were consistently higher in reactors that were sparged with N_2 although the magnitude of the effect varied. The laboratory-measured first order decay rate constants for H_2S and CH_4 production were used to estimate constants that were applicable in landfills. The estimated constants ranged from 0.11 yr~(-1) for C&D fines to 0.38 yr~(-1) for a mixed fly ash and bottom ash from MSW combustion.