Study On The Effect Of Residual Disinfentant On Methane Production By Anaerobic Fermentation

In order to ensure the inspection,quarantine and barrier of animals in livestock and poultry farms,reduce the spread of various diseases and establish a strict and effective biological safety and control system,the use of different types of chemical disinfectants to disinfect the environment and utensils of the farm is recognized as one of the most basic and effective methods.However,residual disinfectants will inevitably be discharged into the methane pool along with livestock and poultry breeding wastes or waste water from cleaning sites and utensils.These residual disinfectants will inhibit the normal progress of the anaerobic fermentation process in the methane pool,resulting in a decrease in the utilization rate of anaerobic fermentation raw materials and gas production rate.Therefore,it is necessary to carry out relevant research on the influence of residual disinfectants on the gas production process and conditions of anaerobic fermentation.In this paper,by selecting the three most commonly used disinfectants in farms,including glutaral and deciquam solution,potassium bisulphate compound powder disinfectant and povidone iodine solution,a customized constant temperature anaerobic fermentation experimental device was used to develop disinfectant’s anaerobic fermentation production.The main tasks of the research on the impact of biogas efficiency are as follows:(1)The results of anaerobic fermentation experiment by adding different concentrations of glutaral and deciquam solution showed that the cumulative gas production of four experimental groups with mass fraction of 0.005%,0.01%,0.025% and 0.05% decreased by 20.05%,47.5%,62.76% and 99.52%respectively after 27 days compared with the control group.At the end of fermentation,the inhibition rate of gas production potential is 12.62%～60.02%.At the same time,glutaral and deciquam solution not only reduces the methane content in the biogas to varying degrees,but also causes the p H of the anaerobic fermentation system to drop,but the overall effect is not obvious.On the other hand,the content of volatile total fatty acids increased,lipase activity decreased,cellulase activity and saccharified amylase activity also decreased,and the correlation between hydrolase activity and gas production rate was not obvious,and the dynamics of enzyme activity and gas production balanced relationship is broken.(2)Adding different concentrations of potassium hydrogen persulfate compound,when the anaerobic fermentation test is over,the inhibition rate on gas production potential is measured to be 14.07%～62.26%.When the additive concentration is low,the effect on the total gas production is not obvious.When the addition concentration was 0.75%(ω),the gas production process of the anaerobic fermentation system was completely inhibited and could not be recovered.At the same time,adding potassium persulfate compound made methane content in biogas decreased and p H value of fermentation system decreased.As a result,the volatile total fatty acids in the fermentation system are excessively accumulated,and the lipase activity,cellulase activity,and saccharification amylase activity are all decreased.Adding low concentration of potassium persulfate complex has little effect on biogas fermentation related enzyme activities,and the enzyme activities of anaerobic fermentation system can quickly recover to the normal level.When the concentration of potassium persulfate compound reached 0.75%(ω),cellulase activity continued to decline and could not be recovered.However,the amylase activity of the saccharified type had a strong tolerance to potassium persulfate complex,and the enzyme activity could be maintained at a certain level,and the decline trend of the enzyme activity slowed down.(3)When different concentrations of povidone iodine solution were added to the anaerobic fermentation system,the experimental results showed that the inhibition effect of povidone iodine solution on the anaerobic fermentation system would be enhanced with the increase of the concentration.The inhibitory rate of povidone iodine on the gas production potential of raw materials is 7.32%～ 49.78%.With the increase of the concentration,the p H value will decrease more,and the content of methane will also decrease.The addition of povidone iodine solution resulted in the accumulation of VFAs and the decrease of enzyme activity.When the supplemental level was 0.5%(ω),the contents of total volatile fatty acids increased by 35.77%,lipase activity decreased by 87.43%,cellulase activity decreased by 89.42%,and amylase activity decreased by 85.72%.(4)The improved Gompertz model was used to theoretically predict the cumulative gas production of disinfectants with different concentrations in the process of anaerobic fermentation,and it was found that the fitting correlation coefficients were all above 0.98,indicating that the fitting was good.It was feasible to use this model to predict the gas production of the anaerobic fermentation system containing disinfectants.By comparing the gas production rate of each experimental group and the cumulative gas production after adding disinfectants,and combining with the inhibitory degree of the disinfectants on the enzyme activity,the inhibition degree of the three kinds of disinfectants on the anaerobic fermentation was comprehensively compared and analyzed as follows: glutaral and deciquam solution > povidone iodine solution > potassium bisulphate compound powder disinfectant.