Propionate-oxidizing bacteria community can oxidize propionate to acetic aid and H2/CO2 which can be used by methanogens, and they occupy a unique niche in anaerobic digestion systems. An understanding for the shift of propionate-oxidizing bacteria in anaerobic wastewater treatment system is of important significance for regulating and operating the process. Impacts of hydraulic retention time (HRT) on performance of an upflow anaerobic sludge bed reactor (UASB) and shift in propionate-oxidizing bacteria community were investigated at mesophilic condition. The results showed that shortening HRT within certain range of 24 h to 8 h, at an influent COD of 1000 mg · L-1, would cause shocks to UASB, resulting in a transient accumulation of propionate and acetate, and after maintaining run for a certain period UASB could achieve new steady states again and keep higher removal efficiency of COD, which were 94.9%, 93.9%, 92.5%, 91. 8% and 87. 9% , at HRT 24, 20, 16, 12 and 8 h, respectively,during these steady states. An obvious change of propionate-oxidizing bacteria community in anaerobic activated sludge was observed when HRT decreased. Syntrophobacter pfennigi was appeared at HRT 24 h and disappeared completely at HRT 8 h, while S. Sulfatireducens, Pelutomaculum and Desulfotomaculum were dominant bacteria at HRT 8 h. Smithella propionica maintained a relatively high richness in whole operational process, indicating its existent in a wide niche. The pollutant removal and running stability of the UASB should be improved by the enrichment of propionate-oxidizing bacteria.%丙酸氧化菌群可将丙酸转化为产甲烷菌可利用的乙酸和H2/CO2,在厌氧产甲烷系统中占据独特的生态位,了解其在厌氧废水处理系统中的变化规律,对于系统的调控运行具有重要意义.考察了中温条件下水力停留时间(HRT)对升流式厌氧污泥床反应器(UASB)的运行效能及丙酸氧化菌群更迭的影响.结果表明,在进水COD为1000mg·L-1条件下,HRT在一定范围内的缩短会对UASB系统造成一定的冲击,短时期内出现丙酸和乙酸的积累,但在维持运行一段时间后可重新达到运行的稳定状态,并保持了较高的COD去除率.在HRT 24、20、16、12、8h条件下的稳定阶段,系统的平均COD去除率分别为94.9％、93.9％、92.5％、91.8％和87.9％.HRT的缩短使系统活性污泥中的丙酸氧化菌群发生了更迭,HRT 24 h条件下居优势地位的Syntrophobacter pfennigii在HRT 8 h条件下消失,取而代之的是S.sulfatireducens,Pelotomaculum和Desulotomaculum,而Smithella丙酸氧化菌具有更宽的生态位,在系统中始终占据一定的优势度.在系统中富集更多的丙酸氧化菌群,可有效提升UASB的处理效能和运行稳定性.
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