Study On Recovery Of Methane Production And Microbial Changes In Anaerobic Acidification System Of Kitchen Waste

With the increasing production of kitchen waste,the disposal of kitchen waste is also imminent.In the process of treating kitchen waste with anaerobic digestion technology,not only more clean energy can be obtained,but also environmental pollution can be reduced.However,due to the high moisture content and high organic material content of kitchen waste,acidification is easy to occur in the process of using anaerobic digestion technology to treat kitchen waste.For this,this experiment adopts the batch fermentation(effective volume is 400 m L),by setting the different concentration gradient of the fermentation reaction system,to explore the eat hutch waste acid concentration in the process of anaerobic digestion and the accumulation of VFA threshold,in acidification concentration for acidification system after a series of acidizing recovery measures,such as adding Na OH buffer solution,activated carbon,and magnet powder,vermiculite,based on the experiments in the process of constituting the recovery period,organic acid content,p H value,methane content,accumulated from domestic production and observe and record the parameters,it is concluded that adding vermiculite etc.Suitable for recovery of eat hutch garbage acidification method of the system.In the process,but also for adding different amount of vermiculite restore the change of the microbial community in the process of acidification is analyzed,it is concluded that the experimental group in the start stage,the main peak stage,stage of acidification,acidification recovery phase,peak methaneproducing phase of the microbial community analysis,to explore the different stages of advantage bacterium group and microorganisms.(1)Determine the threshold of acidification fermentation concentration and accumulation of organic acids.Different fermentation concentrations of 4%,5%,6%and 7% were set for the experiment at 35±1℃.The experimental results showed that when the anaerobic fermentation concentration of kitchen waste was lower than 5%,the anaerobic digestion was normal,and the total concentration of VFAS was less than3000mg/L,acetic acid/butyric acid >1;When the concentration of anaerobic fermentation is 5%,the digestive system is slightly acidified,but the system will recover naturally after a few days.At this time,the total concentration of VFAS is between 3000mg/L and 6000mg/L,and acetic acid/butyric acid >1 after system recovery;When the system is higher than 5%,the digestive system is seriously acidified,and gas production stops and does not recover naturally.At this time,the total concentration of VFAs in the digestive system exceeds 6000mg/L,and acetic acid/butyric acid<1.Therefore,the concentration threshold of anaerobic fermentation of kitchen waste is 5%,and the accumulation threshold of organic acid is 6000mg/L.(2)Methane production was recovered for the acidification reaction system with a fermentation concentration of 6%.The results showed that:(1)When the p H of the acidification system was adjusted to 6.5 by Na OH buffer solution,the best methaneproducing effect could be obtained,the maximum methane content was 63%,and the VS methane production rate was 596 m L/g.(2)When using activated carbon to restore acidification system,the optimal addition amount is 10 g,the recovery period is 15 d,the maximum methane content is 61.4%,and the methane production rate of VS is568 m L/g.(3)When using magnet powder to restore acidification system,the optimal addition amount is 10 g,the recovery period is 17 d,the maximum methane content is60.8%,and the methane production rate of VS is 598 m L/g.(4)When vermiculite was used to restore acidification system,the optimal addition amount was 15 g,the recovery period was 10 d,the maximum methane content was 64%,and the methane production rate was 718 m L/g VS.Taking the above factors into consideration,the best method to restore the anaerobic digestion acidification system of kitchen waste is to add vermiculite,with an amount of 10 g.(3)Analysis of the dominant community in the process of restoring acidification system by adding vermiculite.The results showed that the number of OTU in the acidification system increased with the recovery of acidification.At the phylum level,Firmicutes was the dominant bacteria in the anaerobic digestion of kitchen waste,with the richness of over 60% in all stages,followed by Proteobacteria and Unidentified＿bacteria.At the genus level,the dominant flora in the peak period of hydrogen production were Clostridium＿Sensu＿Stricto＿1,Caproiciproducens and Methanosaeta.The dominant flora in both the acidification stage and the acidification recovery stage are Clostridium＿Sensu＿Stricto＿1,Caproiciproducens and Clostridium＿Sensu＿Stricto＿12.Methane production peaked in Clostridium＿Sensu＿Stricto＿1,Caproiciproducens and Methanosarcina.Methanosaeta and Methanosarcina methane-producing microbes in hydrogen and methane production showed negative correlation.In the acidification stage,the richness of acetic acid producing microorganism was the highest.Through the acidification system to restore the gas production,so as to restore the food kitchen waste acidification system methane production effect,improve the production of methane,to achieve the food kitchen waste resources and energy utilization.