Effect of H_2 addition on the microbial community structure of a mesophilic anaerobic digestion system

摘要

In situ biogas upgrading by H_2 addition is a promising technology to increase the calorific value of biogas ; however, its effects on microbial community structure remain unclear. Therefore, mesophilic digestion of swine manure was carried out in a reactor with an H_2 addition rate of 7.2 mL/min (at a 4:1H_2: CO_2 ratio) and an organic loading rate of 2.0 g of volatile solids (VS)/(L-d). After H_2 was injected into the reactor, the maximum average methane yield increased from 189 to 245 L/kg VS under intermittent mixing conditions. The acetate concentration increased to a maximum of 1600 mg/L but the methane yield was reduced to 210 L/kg VS, which was attributed to a reduction in acetoclastic metha-nogen abundance in the system due to continuous mixing. The combination of homoacetogenic Clos-tridium and the Methanosaeta acetoclastic methanogens instead of hydrogenotrophic methanogens appears to have played a vital role in converting the added H_2 into CH_4 in the mesophilic reactor. However, hydrogenotrophic methanogens accounted for approximately 10% of the total metabolic activity while having a relative abundance of less than 0.5% among the methanogens, after the acetoclastic were inhibited.