| Municipal solid waste landfill, which contains plenty types of microoganism, is an important and huge microbial stock under the interferences of human acitivities.As the main artificial anthropogenic methane emission source, methanogens, methanotrophic bacteria and other bacteria in landfill have a great effect on global greenhouse gas emissions. Study on the microbial community structure and diversity of landfill can provide scientific bases for utilizing microorganism to strengthen the stability of landfill and reducing the methane emissions. By using a typical waste landfill as an example, this program analyzed the microbial community structure and diversity, developed an effective microbial agent for controlling methane and ammonia based on methanotrophic bacteria and NH3 removing strains, and studied the effect of microbial agent through artificial simulated landfill columns. The main research contents and results were as follows:(1) By using the High-throughput sequencing--MiSeq to analyze the microbial community structure and diversity in landfill, the results indicated methanotrophic bacteria and bacteria that promote methane-producing had a certain correlation with the depth of waste soil. Among those bacteria that could oxidize methane, the Methylohalobius were more abundant in cover soil than those in waste soil. Syntrophomonas and Fastidiosipila that played an important role in anaerobic methanogenic phase were only dominated in deep layer of the waste soil (90-150 cm). Combine microbial community diversity with the physical and chemical characteristics of the soils, the conductivity, organic matter content and moisture content were the main factors to influence the microbial community structure in landfill through the CCA analysis.(2) Two samples of methane-oxidizing mixed consortium were isolated from landfill soils. High-throughput sequencing showed that methanotrophic bacteria belong to Methylocaldum. Methylocyslaceae and Methyloversalilis. The other non-methane-oxidizing bacteria included Stenotrophomonas maltophilia and so on. Gas chromatography analysis indicated that methane oxidation ability of the mixed culture was 43.57%-64.97%. The growth curve of mixed consortium indicated methanotrophic bacteria grew slowly and the logarithmic growth phase was about 150-250 h.(3) The factor affecting the activity of methanotrophic bacteria in landfills is NH4. NH3 removing strains can absorb ammonia in the form of NH3 and terminate the inhibition of methane oxidation activity to reduce the methane emissions. Three high efficient NH3 removing strains were selected from six obtained strains, and they were identified by 16SrDNA or rDNA-ITS sequence comparing. Tested by ammonia gas detector, Candida ethanolica and Bacillus cereus had obvious effect in removing the ammonia that volatilized from sludge in opening environment. However, Bacillus cereus and Alcaligenes faecalis were dominant in airtight environment.(4) To verify the effect of microbial agent, food wastes were chosen to anaerobic ferment to produce gas. After flowed through artificial simulated landfill columns the gas was detected by the ammonia gas detector. It was found that the concentration of ammonia showed a downward trend Furthermore, experimental group 1 (methane-oxidizing mixed consortium and high efficient NH? removing strains) had the best effect at 6th-21st day. However, the methane concentrations in experimental group were significantly lower than those in control group, and experimental group 1 had the best effect at 10th-18th day. |
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