Research On Adding Carbon-based Conductive Material To Produce Methane By Enhanced Anaerobic Digestion Of Fat,Oil And Grease

With the increasing demand for energy in the world,anaerobic digestion of organic waste to produce methane has received more and more attention.The treatment of grease in sewage has become an important challenge for my country to maintain public health and strengthen environmental protection.Because of the higher methane production potential of oils,anaerobic digestion of oils has become one of the most attractive oil treatment methods.However,the long-chain fatty acids produced by the hydrolysis of fats and oils inhibit anaerobic microorganisms and hinder the stable operation of anaerobic digestion.The addition of carbon-based conductive materials can effectively promote direct interspecific electron transfer(DIET)between bacteria and methanogens,and improve the efficiency of anaerobic digestion of methane.This method accelerates the metabolism of long-chain fatty acids to increase the production of anaerobic digested oils.The efficiency of methane provides feasibility.The purpose of this study is to explore the effect of carbon-based conductive materials on the enhanced anaerobic digestion of fat oil and grease to produce methane.By studying the effect of adding different types carbon-based conductive materials on the anaerobic co-digestion of grease and remaining activated sludge,it is found that,compared with the control group without conductive material,the addition of nano graphite powder,granular activated carbon and carbon cloth can increase by13.9%,13.4% and 22%,and the best dosage is 0.2 g/L.,10 g/L and 1×5cm2/150 m L(working volume).Compared with the single peak of the methane production rate of the control group,the reaction group with the addition of carbon-based conductive materials observed two peaks of the methane production rate,which is likely to be one of the reasons for the increase in methane production.Both carbon cloth and activated carbon promoted the growth and reproduction of microorganisms,and the copy number of bacteria and archaea was significantly greater than that of the nano graphite powder group and the control group.Through microbial community analysis,it is found that three different types of carbon-based conductive materials promote the synergistic acetic acid oxidation degradation(syntrophic acetate oxidation,SAO)pathway in the anaerobic co-digestion experiment,and DIET-mediated SAO is likely to occur.This approach promotes faster degradation of acetic acid,resulting in more methane production.Among them,the possibility of Exilispira,Thermococci and Candidatus Methanomethylicus,which are relatively abundant in the material group,participates in DIET needs further study.Further study the effect of anaerobic digestion of fat,oil and grease through adding hydrogen.In the process of anaerobic digestion of oil,compared with the control group without hydrogenation and conductive materials,activated carbon hydrogenation and carbon cloth hydrogenation can increase methane production by59.0% and 83.4%,respectively.Hydrogenation enhances the methane production of anaerobic digestion.This is likely to be the result of the action of DIET.When palmitic acid and oleic acid are used as substrates,both the hydrogenated activated carbon group and the carbon cloth group can increase methane production,but when anaerobic digestion of oleic acid,the addition of activated carbon has an inhibitory effect.The degradation effect of palmitic acid and oleic acid is affected by the type of carbon-based conductive material.The analysis of the microbial community showed that Syntrophomonas palmitatica,Syntrophobacter,S50＿wastewater-sludge＿group,Blvii28＿wastewater-sludge＿group,and Methanobacterium and Methanosaeta were enriched,indicating that hydrogenation is likely to strengthen the role of DIET in the degradation of long-chain fatty acids and volatile fatty acids.