Effect Of Hematite And EDTA On Methane Production From Acetate

Environmental problems of air pollution and greenhouse effect caused by the use of fossile fuel are being received more attention all over the world. As a representative of clean energy, the biomass energy arouses passion and concern of the world. Anaerobic digestion process can be adapted to a wide range of substrates and it can dispose organic waste and procuce methane simultaneously. In this present study, the effect of iron oxides on the anaerobic digestion process was invesgated, whether the characteristic of iron oxides or carbon sources were the major determining factors that influenced the function of iron oxides were mainly explored; the effect of hematite and EDTA on anaerobic digestion of acetate, anaerobic degradation of EDTA was investgated in reactor with hematite added.Finally, PCR-DGGE technology was ultilized to explore the microbial community structure.Results showed that, under high organic loading condition, as the inoculated sludge was 0.1 g VS/L and the organic carbon concentration was 2.4g/L, the lag phase was shortened and the generation rate of CH4 and CO2 were significantly enhanced by adding 8g/L hematite. Furthermore, low SSA hematite is superior to high SSA hematite in strengthening methanogenesis in this study. Under low organic loading condition,0.64g/L hematite made no difference to the gereration rate of CH4, while it raised the methane productivity by 14%. Groups with different substrates resulted in different methane productivity with the same organic carbon, the methane productivity of groups with sodium acetate as substrate was over 80%, while that of beef extract groups was 66%-74%.The production rate decreased as the concentration of EDTA increased in groups with 0.64g/L hematite. EDTA inhibited the bioactivity of most microbes, resulted in the delay of start-up time for the methane procuction process and slow down the generation rate of biogas. While addition of hematite would relieve the inhibition from EDTA. In addition, EDTA promoted the dissimilatory iron reduction reaction, which competed with the methanogenesis reaction, thus EDTA resulted the decrease of methane production.The dominant bacteria in control groups was Mesotoga sp. and Clostridium sp.Therelative abundance of Pseudomonas sp. increased in groups with EDTA. Without EDTA, the dominant archaea was Methanosarcina sp., while Methanosaeta sp. was the dominant archaea in groups with high concentration of EDTA.