pH对UASB运行效能及产甲烷互营菌群的影响

Impact of pH on performance and syntrophic community of hydrogen-producing acetogens and methanogens in an UASB

研究产甲烷互营菌群对pH变化的响应,对于寻求提高有机废水厌氧生物处理效能的策略具有重要意义.以处理制糖废水的升流式厌氧污泥床(UASB)反应器的运行为基础,考察不同pH对反应器运行效能及产甲烷互营菌群的影响.结果表明,在进水COD 20 000 mg.L-1、HRT 8 h的条件下,当进水pH分阶段由6.9降至5.4时,UASB系统的pH随之从6.8～7.4下降至5.7～6.7,导致COD去除率降低了23.3%,出水中残留丙酸提高了3.9倍.聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)分析结果表明,产氢产乙酸菌群在UASB中的多样性显著低于产甲烷菌群,其分布和优势度受pH降低的影响显著.以Eub 19(Pelotomaculum)为代表的食丙酸产氢产乙酸菌在偏酸环境中的优势度明显减弱,而食乙酸产甲烷菌及部分食氢产甲烷菌对pH下降响应并不显著,且随着pH下降,耐酸的食氢产甲烷菌Methanobacterium ferruginis和Uncultured Methanobrevibacter的优势度逐渐增强.由此可见,与产甲烷菌群相比,UASB系统中的产氢产乙酸菌群对pH的变化更加敏感.

An mesophilic upflow anaerobic sludge bed（UASB） reactor treating sugar refinery wastewater with an influent COD 20 000 mg·L^-1 and HRT 8 h was introduced,and the impact of pH on its performance and hydrogen-producing acetogens and methanogens were investigated.The results showed that the pH in the UASB dropped from 6.8-7.4 to 5.7-6.7 when the influent pH decreased from 6.9 to 5.4,resulting in a reduction in COD removal by 23.3% and a propionate increase in effluent by 3.9 times.Polymerase chain reaction-denaturing gradient gel electrophoresis（PCR-DGGE） of sampled sludge indicated that the diversity of hydrogen-producing acetogens in the UASB was remarkably lower than that of the methanogens.The distribution and dominance of hydrogen-producing acetogens had been observably influenced by the dropped pH.The dominance of propionate-oxidizing bacteria（Pelotomaculum）,represented by band Eub 19,were significantly reduced in approach acid condition,while acetotrophic methanogens and the dominant hydrogenotrophic methanogens stood steadily.Furthermore,the dominance of some acid-tolerant hydrogenotrophic methanogens such as Methanobacterium ferruginis and uncultured Methanobrevibacter were enhanced observably following the drop in pH.These results suggested that hydrogen-producing acetogens seemed to be more susceptible to pH than methanogens.