Study On The Characteristics Of High Temperature Dry Anaerobic Fermentation Of Bean Dregs And Cattle Manure

Tofu is a traditional Chinese food,with the increasing number of soybean processing factories,the production of bean dregs has become a major problem in the treatment.The water content of bean dregs is large,which is easy to deteriorate and produce the stench under normal temperature,It can not be preserved for a long time,so that cause environmental pollution.Bean dregs contain rich nutrients and trace elements,which are beneficial to the growth and reproduction of microbial community in the process of anaerobic fermentation,but it is easy to accumulate a large amount of volatile fatty acids in a short period of time,leading to fermentation failure.Bean dregs is not suitab le for anaerobic fermentation alone.cattle manure is a kind of common fermentation raw material with strong buffering ability,but its nutrient composition is less,separate methane fermentation yield is low.Therefore,in this study,the mixture of bean dregs and cattle manure was used as the anaerobic fermentation raw material.Under the condition of high temperature and high substrate concentration,the effects of substrate concentration,inoculation ratio and material mixture ratio on the gas productio n performance of anaerobic fermentation process were investigated;analyzed the changes of pH,volatile fatty acids and biodegradation rate during anaerobic fermentation;optimized the influencing factors by response surface method to obtain the optimal pr ocess parameters of cumulative volumetric gas production rate and cumulative methane production of volatile substance.The main findings and conclusions were obtained as follows:The results of single factor test show that the increase of substrate concentr ation,increased biogas production,extended residence time,mixed material fluidity became worse;inoculation ratio increased,shorten the delay period,improve the stability of the fermentation system,The appropriate inoculation ratio is more conducive to the start-up of fermentation system;Increasing the mixture ratio of bean dregs and cattle manure,biogas production,methane content and biodegradation rate increased,suitable material mixing ratio can provide more sufficient nutrients for microbial flora and improve the utilization rate of organic materials.When the substrate concentration was 14%,the inoculation ratio was0.175:1,and the material mixture ratio was 6:4,the cumulative methane production of volatile substance,methane content and b iodegradation rate were the highest in the same group.Through the analysis VFAs content and pH of anaerobic fermentation index,it was found that the change law of all test groups were basically the same,the VFAs content increased rapidly to the peak va lue,and pH decreased rapidly in the early stage of anaerobic fermentation.With the utilization of VFAs by microbial community,the VFAs content decreased gradually and the pH increased gradually,all test groups pH remained in the range of 6.52～7.93.The inoculation ratio has significant effect on VFAs content,when the inoculation ratio is 0.1:1,the VFAs peak of I1 was significantly higher than that of I2～I5,11.95 g/L;with the increase of the materials mixture ratio,the peak value of VFAs gradually increased,the fluctuation changed greatly and the peak appeared many times.Based on the single-factor test results,optimization using variance analysis and response surface showed that: single factor analysis,it can be concluded that the substrate concentration has a significant impact on the cumulative volumetric gas production rate,and the substrate concentration interacted with the material mixture ratio;the inoculation ratio and material mixture ratio on cumulative methane production of volatile substance was very significant,and the substrate concentration was insignificant.The interactions between the three factors were not significant.According to the regression model,the optimized process parameters were substrate concentration of 15.04%,in oculation ratio of 0.19:1 and material mixture ratio of 1.51:1.Under the optimal conditions,the cumulative methane production was 85149.1 m L and the cumulative methane production of volatile substance was 316.91 m L/g VS,the relative error was 0.07% and 0.30%,respectively;the predicted value was reliable.