The Research On Methanogens Diversity And Optimization Of Methane-producing Efficiency In The Sludge

Currently, anaerobic digestion is the most widely used method of disposing urban sludge, which approaches to enable sludge reduction and recycling. In the process of anaerobic digestion, methane, the main composition of bioga, mixed with oxygen produces a lot of energy after combustion, and oxygen to produce biogas anaerobic digestion process to produce mixed burning a lot of energy, and energy efficiency is significantly higher than firewood, straw, coal, etc. So anaerobic digestion energy has practical applications prospect in China in which consumption of energy sources is huge and energy conservation and emission reduction is promoted. As the core of microorganism in anaerobic digestion, methanogens is also an integral member of the last natural carbon cycle anaerobic fermentation, the pros and cons of methane-producing bacteria directly affect the level of efficiency of anaerobic digestion, thus obtaining stable and efficient methanogens is very meaningful. So, firstly this article enriched five bacteria sources to obtain methane-producing advantage bacterium group, and combined with DGGE to analysis the diversity of methanogens flora structure, then selected the sample with most methane gas production which was used to study the influence factors of methanogens, on this basis, optimized methane production efficiency of methanogens using response surface method. During subculture of five bacteria sources, methane production capacity had been increased to varying degrees after four times subculture of methanogens, and the largest accumulation of methane-producing was the laboratory anaerobic digestion sludge, for3.964L/L, the minimum accumulation of methane-producing was Lin’s biogas anaerobic digester sludge, for1.691L/L. Analysis of PCR-DGGE profiles of five kinds of anaerobic bacteria group showed that, microbial flora of five samples were all abundant. And analysis of DGGE bands sequence found that11kinds of archaea with similarity of98%or more to the existing sequences. Dominant bacterial community belonged to seven genera, respectively Methanosaeta, Methanocorpusculu, Methanogenium, Methanoculleus, Methanomicrobials, Methanosarcina and Methanoplanus. Due to anaerobic fermentation tank sludge enrichment was best and produced maximum amount of cumulative methane, selected this bacteria source as experimental material for subsequent experiments to study influencing factors to methanogens and optimization of methanogenic performance.In the study of the influence factors of methanogens, mainly inspected on pH, inoculum size, nickel chloride, cobalt chloride, ferrous sulfate impact these five aspects. The study found:pH6.8, the cumulative production of methane, biomass, formic acid utilization and methane production rate showed the maximum and when the pH was7.0, the methane content, methanol utilization, acetic acid utilization showed the maximum. When inoculation amount was10%, methane content, the cumulative amount of methane production, the pH at the ending and the utilization of three substrates presented the maximum. When the concentration of ferrous sulfate was0.15g/L and0.20g/L respectively, the cumulative production of methane and biomass reached a maximum value,14.07L/L and0.468g/L respectively. When cobalt chloride and nickel chloride concentrations were0.15g/L and0.03g/L respectively, the various physiological indicators of methane-producing bacteria showed maximum.On the basis of single factor affecting the methanogenic performance experimental analysis, the above five factors as the main factors and accumulate methane amount as the response value, applied the design principle of Box-Behnken central composite, designed5factor2levels sum to46experiments to response surface analysis. After the results of response surface and analysis of variance, obtained optimal experimental conditions for pH6.8, inoculum13.29%, CoCl20.15g/L, NiCl20.02g/L and FeSO40.19g/L. In this condition, the cumulative amount of methane produced reached4.21L/L,6.21%higher than the cumulative production of methane enriched by methanogenic bacteria after four times, similar with the predicted values, indicating that this model can truly reflect how the various main factors affect the cumulative amount of methane production.