|Other Abstract||This dissertation studied on the distribution and change of microbial community structure in activated sludge and wetland substrate from SMBR-IVCW integrated system under different operating conditions. 16S rDNA, FISH, PLFA and assay of enzyme activity were applied and chemical properties of water quality were measured for disclosing the relationship between microbial community structure and function. The results of this study were supposed to clarify the purification mechanisms of the integrated system and contribute to the theoretical basis for optimizing the operation and management. The main results were summarized as follows:
1. A 16S rDNA clone library was generated and 150 clones was screened using technology of restriction fragment length polymorphism (RFLP). Of the screened clones, almost full-length 16S rDNA sequences of 64 clones were sequenced. Phylogenetic tree was constructed with a database containing clone sequences from this study and bacterial rDNA sequences from NCBI (http://www.ncbi.nlm.nih.gov/) for identification purposes. 90.6% of the clones were affiliated with the two phyla Bacteroidetes (50%) and Proteobacteria (41%), and, Beta-, Gamma- and Deltaproteobacteria accounted for 7.8, 28.1 and 4.7%, respectively. Minor portions were affiliated with the Actinobacteria and Firmicutes (both 3.1%). Only six out of the 64 16S rDNA sequences exhibited similarities of more than 97% to classified bacterial species, which indicated that a substantial fraction of the clones were derived from unknown taxa. Rarefaction analysis of OTUs (operational taxonomic units) clusters demonstrated that 150 clones screened were still insufficient for describing the whole bacterial diversity. Measurement of water quality parameter demonstrated that performance of the SMBR was highly efficient and the SMBR system remained stable during this study. The nucleotide sequence data reported in this study have been deposited in the NCBI nucleotide databases under the accession numbers EU283346 to EU283409.
2. The performance and PLFA analysis of SMBR and enzymatic activities of activated sludge at different pollution loads were assayed. The results showed that: the removal rates of COD、TN、TP and NH4+-N were kept at high and stable levels and the differences were not significant at different pollution loads(p＞0.05); the enzymatic activity of phosphatase was the highest at low pollution load, activities of dehydrogenase and β-glucosidase at low and middle pollution loads were higher than that at high pollution load, and activities of urease and protease increased with pollution load; monounsaturated PLFAs, saturated PLFAs and branched PLFAs were dominant PLFA types, while polyunsaturated PLFAs and cycloproply PLFAs were present with relative small amount and ratios of characteristic fatty acids showed that aerobic prokaryotes were the most important groups; analysis of microbial community structure revealed that aerobic prokaryotes were predominant groups in activated sludge, followed by the gram-positive prokaryotes and other anaerobic bacteria group, and the percentage of microeukaryotes group was the lowest.
3. PLFAs composition of substrate from IVCW was used as biomarker of microbial community structure, and assay of enzyme activity was applied for disclosing the activity of microbe and its functions. The even numbered saturated PLFAs, monounsaturated PLFAs and polyunsaturated PLFAs were the most important and dominating fatty acid, and branched PLFAs, odd numbered saturated PLFAs and cycloproply PLFAs were present with relative small fraction; ratios of characteristic fatty acids showed vertical distribution pattern; aerobic prokaryotes in substrate were predominant groups, followed by the gram-positive bacteria and other anaerobic bacteria; and microeukaryotes accounted for the lowest proportion. The distribution of biomarker PLFAs of microbial functional groups indicated that there were distinct aerobic and facultative anaerobic function areas in the wetland system. Enzyme activities of substrate were related with direction of water and the pollution load, and except for phosphatase, enzyme activities were high at surface and low at subsurface.
4. Numbers of total bacterium and eubacterium in SMBR-IVCW integrated system were evaluated by FISH. The results disclosed that numbers of total bacterium in activated sludge, substrate of wetland at middle pollution load and activated sludge in adaptive phase were 2.241011 g-1, 2.51010 g-1 and 1.81010 g-1, respectively. And, percentages of EUB338/DAPI were 54.9%, 72% and 38.9% in different samples, respectively.|