The Community Structures And Functions Of Ammonia Oxidizing Bacteria And Bacteria In Wastewater Treatment Plant

Municipal wastewater is a major pollution source to water bodies in China. Biological treatment process is the most efficiently and widely used method to treat municipal wastewater. In biological wastewater treatment plants, bacteria play the key role in pollutant removal. Therefore, a better understanding of the bacterial community structure and function in the treatment system can help to elucidate the mechanism of biological pollutant removal and then to enhance the treatment performance and stability. In this study, a number of molecular techniques and statistical methods were used to analyze the community structures of ammonia oxidizing bacteria (AOB) and bacteria in several wastewater treatment plants. The factors that affect the microbial community structure were identified. The relationship between microbial community dynamics and system function was analyzed.The FastDNA? Spin Kit for Soil was selected as the efficient DNA extraction method for activated sludge samples based on the comparative analysis of three different methods. The conditions of PCR amplification were optimized. A set of molecular methods for examining the microbial community structure in activated sludge was established.The AOB and bacterial community structures in 9 wastewater treatment systems were examined by using the terminal restriction fragment length polymorphism (T-RFLP) and clone library. The results showed that there was no remarkable difference among the AOB and bacteria T-RFLP profiles in the activated sludge samples taken from different parts of the same aeration tank. The treatment process had no conspicuous effect on the AOB and bacterial communities, while plant scale had some effect on the AOB and bacteria community. The influent composition influenced the AOB and bacterial community notablely. The corresponding species of 4 different AOB terminal restriction fragments (T-RFs) and 57 bacterial T-RFs were determined by comparing the results of T-RFLP and sequencing of clones.The community dynamics of AOB and bacteria in several wastewater treatment plants were analyzed by using T-RFLP, qPCR and Moving window Analysis. The results showed that in two functionally stable full-scale wastewater treatment systems, the AOB community changed at a low level. While in five functionally stable wastewater treatment systems, it was observed that the bacteria community changed at a medium level, suggesting the functional stability of organic pollutant removal did not correlate with the stable bacterial communities. Based on the results of Detrended Canonical Correspondence Analysis (DCCA), the effluent concentrations of ammonia, water temperature and dissolved oxygen had significant impacts on the AOB community structure. In a pilot-scale wastewater treatment system, the results of qPCR analysis showed that the total number of AOB highly correspond with the removal rate of ammonia. These results pave the way for establishing a dynamic model to describe the ammonia removal performance.