Sulfate Reduction Behavior Of The Mineralized Refuse From Landfill With Oxygen Exposure

Landfill is the main treatment method for municipal solid waste(MS W).The conflict between the daily volume increase of MSW and the limited land resources makes the reclaimation and reutilization of stabilized MSW landfill site possible.Once the landfill is subjected to reclaim,the mineralized refuse will directly expose to air.In this process,the generation of hydrogen sulfide(H2S)needs attention due to it directly decides the choice of the secondary pollution control measures for landfill.In this study,the H2S release behavior under oxygen exposure from mineralized refuse was investigated.The results showed that when the mineral refuse were exposed to oxygen for a long-term,the release of H2S could be greatly promoted and the highest concentration could amount to 5.54 mg/m3.Moreover,the co-exposure of 02 and chloroform could further imporve the H2S production behavior,in which the highest concentration could reach to 40.91 mg/m3.Subsequently,the mixed functional bacteria with sulfate-recduing ability were enriched from the mineralized refuse and its sulfate reduction process was studied under oxygen exposure.It was found that the mixed functional bacteria could reduce the sulfate to H2S,methyl mercaptan and methyl sulfide,the three typical reducing sulfur compounds,under oxygen exposure.The introduction of electronic shuttle(riboflavin)and carbon source(sodium acetate)acclerated the sulfate reduction process by promoting electron transfer rate,in which the highest H2S concentration of 1098 mg/m3 was observed.Finally,the electron donor/acceptor utilization behavior of the mixed functional bacteria under oxygen exposure was studied.This indicated that the mixed functional bacteria could stably produce H2S by aerobic sulfate reduction using SO42-and S2O32-as electron acceptors,respectively.Comparatively,S2O32-was more easily to be utilized,and the sulfate reduction process showed typical antioxidant characteristic.Moreover,the mixed functional bacteria can reduce sulfate with carboxylate and S2O32-as electron donor and acceptor,respectively.Lactate was easier to be utilized than butyrate and acetate.A combination of multiple mechanisms,including enhanced carbon source,electron transfer,may cause mixed functional bacteria to undergo strong aerobic sulfate reduction even under low abundance of sulfur-metabolized microorganisms.However,the role of 02 in this process needs further study.The conclusions obtained in this study may provide some theoretical value for discussing the sulfate reduction process when anaerobic mineralized refuse exposes to 02.