Study On Anaerobic Methane Production Of Short Chain Fatty Acids Enhanced By Goethite And Hematite

Anaerobic digestion has a great prospect in bio-resource utilization and renewable energy field.However slow fermentation rate,low utilization rate and low methane production efficiency limite utilize of methane.How to improve methane production rate and methane efficiency is one of the most important research fields in anaerobic digestion.This paper attempts to investigate the effect of iron oxides(goethite and hematite)on the methane production of short chain fatty acids.Through the construction of short chain fatty acids as substrates of the batch anaerobic digestion system,study on microbial inoculum,feed ratio and micro iron oxide additives respectively on anaerobic digestion and microbial community;structure a long-term culture system,explore long-term effect of goethite and hematite system of short chain fatty acids in anaerobic digestion.(1)Batch experiments indicated that goethite and hematite add to acetic and butyric acid system can improve the methane efficiency and methane production rate,in the range of experiment,promotion effect was increased with the addition of iron oxides;acceleration of propionic acid is weak.60 mM substrate concentration and 2000 mg/L iron oxides has the great accelaration,methane efficiency of three kinds of substrates increased 7.07%,26.28% and 5.79% respectively,the maximum methane production rate increased 44.95%,19.99% and 68.49% respectively.Methanothrix was dominant strains in acetic acid group at low substrate concentration;Methanosarcina could utilize substrate more efficiently under high concentration.Methanothrix is one of acetotrophic methanogens and was the dominant species in propionic acid group.Methanospirillum,Methanothrix and Methanosarcina were main methanogens in butyric acid system,with can both use acetate and H2/CO2 for methane production.(2)Long-term cunture study found that,addition of goethite and hematite can accelarate methane production in three methane cycles,the second cycle has the most significant effect,third cycle gradually weakened.Methanogenesis mainly affect by the microorganisms better than goethite and hematite,the maximum methane production rate were increased by 57.17%,31.75% and 37.19%,respectively,methane efficiency increase 6.51%,11.55% and 9.72%,respectively.The process of goethite and hematite can promote short chain fatty acid production by anaerobic digestion of methane,but with the progress of reaction caused by goethite,hematite and the promoting effect is weak,microorganisms adapt to the reaction system becomes a factor of efficient substrate digestion and methane production.Anaerolinaceae and Methanobacteriaceae form a high efficient production of acetic acid methane production system.