Acidification And Microbial Diversity In An Anaerobic Baffled Reactor

ABR is a highly efficient anaerobic biological treatment process. However, acidification problem has now restricted its application and promotion. The reason of acidification is that mass transfer balances between different anaerobic bacteria were destroyed. Therefore, the research of anaerobic bacteria is important to solve the problem of acidification and improve the performance of reactor. Previous studies mainly focused on methanogens, and less paid attention to the H2-producing acetogenic bacteria and H2-consuming acetogenic bacteria. In particular, it is lack of research about microbial succession process and diversity.COD removal rate, granular sludge form and particle size in ABR startup procedure were investigated. FISH and PCR-DGGE techniques were used to study the microbial community structure and different bacteria in the anaerobic granule sludge were quantified. The results showed the relative abundance of eubacteria is higher than that of archaea. Hybridization of some H2-producing acetogenic bacterium with the probe SmiSR354 is more than those with probe SYNM700. Methanomicrobium Methanomicrobiales have greater ability to adapt to the environment compared with H2-producing acetogenic bacterium hybridized with the probe SmiSR354 and with probe SYNM700. Anaerobic microbial succession was roughly divided into three periods:Inoculation, succession, and stability.The SEM, FISH and PCR-DGGE techniques were used to analyze the bacteria in different chambers of ABR. The microbial morphology, the relative abundance, the community structure and the phylogenetic analysis of the dominant eubacteria were investigated. The results showed that the rod-shaped bacteria were the dominant microbes in the sludge granules. The bacteria in the front chambers had the higher activity than that in the other chambers. The anaerobic fermentation worked mainly in the front part of the ABR, while the methanogenesis worked mainly in the back part. The obvious staged and multi-phased characteristics were observed in the ABR.The typical characteristics of acidification process, such as pH, COD, VFA and microbial morphology, in an ABR were investigated. And by use of the FISH, the population distributions of bacteria were analyzed. The results showed that the ABR reactor was acidified gradually from front to back. Additionally, it can be found that in the acidification process, several crucial bacteria in anaerobic digestion were sharply decreased, such as butyrate-oxidizing acetogenic bacteria syntrophomonas spp, propionate-oxidizing acetogenic bacteria syntrophobacter wolinii, homoacetogenic bacteria acetobacterium species E. limosum, methanomicrobium methanomicrobiales. All these resulted in the upsetting of the mass transfer balances between different anaerobic bacteria.To better understand the growth characteristics of key species, the preliminary test carried out. It established the method of detecting VFA by gas chromatography. It concluded that pH=8 is suitable habitat to eubacteria hybridized with the probe EUB338 and H2-producing acetogenic bacteria hybridized with the probe SmiSR354.