沼气微氧发酵过程硫转化及微生物群落

SULFUR TRANSFORMATION AND MICROBIAL COMMUNITY IN MICROAEROBIC FERMENTATION OF BIOGAS

以水稻秸秆与猪粪为原料,探究微氧发酵过程中S元素的转化与微生物群落特征以及通氧量的影响。结果表明,厌氧发酵过程中原料的S元素约有65.7%转化为H2S进入沼气,19.0%进入发酵后的沼液,15.3%残留在沼渣中。微氧条件下,沼液中S2-的浓度(100 mg/L)远低于厌氧条件的250 mg/L,约71.8%的S元素转化为H2S然后被氧化成为S单质和少量SO42-。H2S去除效率随通氧量的增大而增大,当通氧量为11.85 L/m3沼气时,约96%的H2S被氧化脱除。根据高通量测序结果,与厌氧发酵相比,在微氧条件下,沼液中微生物多样性仅有轻微变化,比较稳定;硫氧化菌明显增多,而产甲烷菌无明显变化。较高浓度硫氧化菌的存在,有利于沼气中H2S的及时转化,可减轻H2S对产甲烷菌活性的抑制,从而促进厌氧发酵的进行。

The introduction of trace oxygen into the anaerobic fermentation system can effectively reduce the concentration of H2S in biogas and realize in situ desulfurization of biogas. The effects of sulfur element transformation,microbial community characteristics and oxygen input quantity on microbial fermentation were studied by using rice straw and pig manure as substrate. The results showed that about 65.7% of the sulfur in the raw material was converted into H2S in the biogas in the process of anaerobic fermentation,19.0% entering biogas slurry after fermentation,and 15.3% remained in biogas residue. Under the condition of micro-oxygen,the concentration of S2-in biogas slurry(100 mg/L)is much lower than 250 mg/L at anaerobic conditions. About 71.8% of sulfur is converted to H2S and then oxidized into S element and a small amount of SO42-. H2S removal efficiency increases with the increase of oxygen,and when the oxygen input quantity11.85 L/m3 biogas,about 96% of H2S is oxidized. According to the results of high-throughput sequencing,under micro aerobaces condition the microbial diversity in slurry only changed slightly and the sulfur-oxidizing bacteria increased significantly compared with that of anogenic fermentation,but methanogens does not change significantly. The presence of higher concentrations of sulfur-oxidizing bacteria can enhance the conversion of H2S timely and reduces the inhibition of H2S to methanogenic bacteria.