The Conversion Of Sulfur Compounds And CH₃SH Production Potential During The Anaerobic Degradation Of Landfilled Waste

Landfill odor pollution is one of the major problems of public environmental complaints,which is one of the main reasons that cause the NIMBY effect?Not-In-My-Back-Yard?.Sulfur compounds are the main sources of odor in landfills.Because of the extremely low odor threshold,CH₃SH has significant effect on landfill odor pollution.In this study,fish and pork waste which were rich in sulfur amino acids were used as the experimental materials.The production of CH₃SH,conversion of sulfur compounds and succession characteristics of microbial community were investigated during the anaerobic degradation of the fish and pork waste.Meanwhile,the production rate and yield of CH₃SH were studied during the anaerobic degradation used the biodegradable components of municipal solid waste?MSW?as the experimental materials.Based on the production of MSW in various provinces in China,the CH₃SH production potential of landfills was predicted.These results would be helpful to assess environmental risk of odor gases produced from landfills and develop techniques to control the odor pollution in landfills.The main results are as follows:?1?Sulfur reduction in the solid phase was mainly converted into gases during the anaerobic degradation of MSW.H₂S,CS2,CH₃SH,CH₃CH₂SH,dimethyl sulfide,dimethyl disulfide and dimethyl tisulfide were the main sulfur gases produced from the anaerobic degradation of fish waste,while H₂S,CH₃SH,dimethyl disulfide and dimethyl tisulfide were the main sulfur gases produced from the anaerobic degradation of pork waste.?2?During the anaerobic degradation of fish and pork waste,the CH₃SH concentration showed a trend of decline after a peak.The maximum of the CH₃SH concentration was 4.96-5.25%during the anaerobic degradation of the two wastes.Compared with the pork waste,methionine,cysteine and total amino acids in the fish waste were degraded more quickly.The cumulative production of CH₃SH from the fish waste was 28.12 L kgdw^-1,which was significantly higher than that from the pork waste.?3?Miseq sequencing analysis showed that Proteobacteria,Firmicutes,Fusobacteria,Bacteroidetes and Actinobacteria dominated in the fish and pork waste during the anaerobic degradation.Among them,Proteobacteria was the main microbe in the fresh fish and pork waste.With the anaerobic degradation of the fish and pork waste,the abundance of Proteobacteria showed a trend of decline,while Firmicutes,Fusobacteria and Bacteroidetes became the main microbes.Acinetobacter,Clostridium,Proteus,Thiobacillus,Hyphomicrobium and Pseudomonas were the main microbes of sulfur metabolism during the fish and pork waste degradation.Acinetobacter was the main microbe of initial sulfur metabolism,while Clostridium was the main microbe of whole sulfur metabolism in the fish and pork waste.?4?With the process of anaerobic degradation,the diversity of microorganisms in the fish waste declined,while it increased in the pork waste.The microbial community was different between the fish and pork waste during the anaerobic degradation.Because of the different composition of the fish and pork waste,the microbial community structure was also different between two wastes,which varied with the time of the anaerobic degradation.During the anaerobic degradation of fish and pork waste,the environmental factors affected the microbial community structure of waste with the following order of importance:C/N>TS>total amino acids>S^2->Cys ? Met>SO42->TOC.Among them,C/N,TS,total amino acids,S^2-,Cys and Met had significant influence on the microbial community structure?P<0.1?.?5?The CH₃SH was mainly produced in the initial stage?in the first 24 days?of the anaerobic degradation of MSW.During the initial stage,the total cumulative CH₃SH production accounted for 92.4-96.7%of the total production from the rice,flour food,vegetable and toilet paper waste,accounted for 79.7%of that from the fish and meat waste,and 63.1-67.6%of that from the yard waste and cellulose textile waste.CH₃SH was mainly produced from the anaerobic degradation of the fish and pork waste,which was 5-6 orders of magnitudes higher than that from the rice,flour food,vegetable,toilet paper and cellulose textile waste.?6?Based on the CH₃SH production from the experimental waste and the landfilled amount of MSW in provinces in China,the CH₃SH production from landfills was predicted.The results showed that the CH₃SH production potential was higher in the coastal provinces in China,of which the highest CH₃SH production potential(8.85×10⁴ m³ yr^-1)was observed in Guangdong province,followed by Shanghai(5.37×10⁴ m³ yr^-1).The CH₃SH production potential from landfills in Zhejiang,Jiangsu,Fujian,Beijing and Liaoning was 3.19×10⁴-4.94×10⁴ m³ yr^-1.The CH₃SH production potential from landfills in inland provinces was relatively lower,which was 2.2×10³-9.74×10³ m³ yr^-1.