Study On The Diversity Of Ammonia Oxidizing Bacteria In Municipal Wastewater Treatment Plants

Sewage nitrogen removal is very important for the control of nitrogen pollution and recycling balance in the nature. Oxidization for ammonia to nitrite which is the first step for nitrogen removl has been considered as the rate-limitated step in the removal process. Therefore, study the main functional microbe for oxidization of ammonia-ammonia oxidizing bacteria (AOB) in municipal wastewater treatment plants (MWTPs), and the relationship between community diversity of AOB and full-scale wastewater treatment systems, which are necessary for optimizing municipal wastewater treatment systems. In this thesis, fluorescence in situ hybridization (FISH), polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and TA cloning techniques were applied to investigate and analyse the community dynamics and structure of AOB in ten treatment systems of seven MWTPs in Beijing.DGGE images results indicated that the community stricture of AOB appeared certain differences between different plants, though the existence of same processes between some different plants. On the other hand, the community stricture of AOB appeared no obvious difference in the same plant despite different processes. And the community stricture of AOB also appeared no obvious difference between different phases in a single process reaction tank.Quantity results of cloning indicated that the AOB number of J plant was much more than that of the second period of Q plant, which may be a factor which affected the efficiency of ammonia removal between the two systems.Sequence results indicated that the diversity of AOB in these systems was generally low, and most of them were grouped into Nitrosomonas oligotropha-like cluster. And some were grouped into Nitrosomonas eutropha-like cluster, and a few were grouped into Nitrosospira. Analysis results of both DGGE and cloning indicated that it was little that the effect of factors within these processes on community structure of AOB with the same influent, when stable among different MWTP systems. Raw water quality and its microbial community structure might be the most important factors in affecting the diversity of AOB in MWTP systems. Meanwhile, the results appeared to be consistent between PCR-DGGE and cloing. Besides, the specificity of CTO primers forβ-AOB 16S rRNA was not perfect for MWTP system analysis.FISH results indicated that FISH was found to be not suitable for quantification and dynamics analysis of AOB in MWTPs. Operating conditions, sensitivity and specificity of probes, fluorescence microscope, counting, sample concentration, phenomena of self-fluorescigenic cells, existence of micro animals, and so on, all may influence the final results of FISH.