Research On Enhancing Anaerobic Digestion Of Excess Sludge By Using Conductive Medium And Biogas Slurry Reflo

With the promotion and application of anaerobic digestion technology,methane as a byproduct of anaerobic digestion,methane production is not negligible,and in-situ reflux of methane to anaerobic digestion system is a more economical and ideal choice to treat methane,but in-situ reflux of methane still has problems such as ammonia nitrogen inhibition,volatile acid inhibition and difficult to degrade substances.It has been shown that the introduction of conductive media into the anaerobic system can promote interspecies electron transfer(DIET)between mutualistic microorganisms,which can effectively reduce the influence of unfavorable factors in anaerobic digestion and thus enhance the efficiency of sludge anaerobic digestion gas production.In view of this,this study investigated the effect of different methane reflux ratios on anaerobic digestion of sludge with municipal residual sludge as substrate,and clarified the optimal reflux ratio of methane reflux to anaerobic digestion system;the effect of methane reflux on anaerobic digestion of sludge based on two different conductive materials(zero-valent iron and activated carbon)was investigated.The effect of different methane reflux ratios on the process of anaerobic digestion system was investigated.Six different sets of methane reflux ratios(0%,20%,40%,60%,80%,100%)and a set of clear water reflux on sludge anaerobic digestion experiments were set up on the basis of the optimal methane reflux.Two experiments were conducted to test and analyze the gas production characteristics,sludge conductivity,metal ion morphology changes and other indexes during anaerobic digestion,and the results showed that: the gas production efficiency increased with increase in the reflux range of 0%-60% of the methane reflux ratio,and decreased with increase in the reflux ratio when the reflux ratio was in the range of 60%-100%,and the ranking of its cumulative biogas production effect was 60%>80%>40%>20%>100%>blank,and 60% of the reflux has the best effect on the cumulative gas production of sludge anaerobic digestion,and the cumulative gas production is increased by17.81% compared with the blank group.However,the methane reflux made the rapid generation of propionic acid in the system,and the larger the reflux ratio the higher the concentration of propionic acid in the system,which increased by 13.36%-89.69% compared with the blank group,and the efficiency of gas production in the pre-methane reflux was inhibited compared with the blank group due to the rapid increase of propionic acid in the system at the pre-aerobic digestion stage,which led to the accumulation of propionic acid in the system.The effect of two different types of conductive materials,zero-valent iron and activated carbon,on the anaerobic digestion of sludge was investigated.Based on the optimal reflux ratio of methane,400 mesh 10 g/L of zero-valent iron powder and 100 mesh 10 g/L of activated carbon powder and the corresponding inert materials were added,as well as setting up a clear water reflux as a blank control group.The corresponding gas production characteristics,sludge conductivity,metal ion morphology,enzyme activity changes and microbial community were analyzed,and the results showed that both zero-valent iron and activated carbon could promote the hydrolytic acidification stage,but the promotion pathways of the two conductive materials were different,and the zero-valent iron synergized with methane reflux mainly promoted hydrolytic acidification to produce more acetic acid,which provided sufficient substrate for methanogenic bacteria;while activated carbon synergized with Both zero-valent iron and activated carbon mitigated the effect of methane production inhibition due to the accumulation of propionic acid in the methane reflux system.Zero-valent iron and activated carbon together with methane reflux promoted the gas production effect of anaerobic digestion of sludge,and their cumulative gas production increased by 13.60% and 18.07% compared with the blank group,increased the abundance of hydrolytic acidifying bacteria Proteobacteria,and zerovalent iron promoted the enrichment of hydrotropic methanogenic bacteria Methanolinea and Methanobacterium.Activated carbon promoted the enrichment of MethanobacteriumThe study shows that the conductive medium in cooperation with the methane reflux can effectively strengthen the sludge anaerobic digestion process and improve the gas production efficiency,and the injection of conductive medium can effectively mitigate the negative impact of methane reflux on sludge anaerobic digestion.The comprehensive application of biogas liquor resourceization and sludge resourceization is proposed as a feasible solution with certain engineering practice application significance.