Research On Microbial Community Structure Of Phosphorus Removing Bacteria In MBR And Conventional Wastewater Treatment Systems

Phosphorus removal has become one of most important indexs for municipal wastewater treatment plants. In all wastewater treatment plants the phosphate removing bacteria——phosphate accumulating organisms(PAOs) play a key role in phosphorus removal systems, so different community structures cause different phosphorus removal efficiency. In conventional sewage treatment systems, the phosphorus removal efficiency is usually lower than that of nitrogen because of the contradiction between nitrogen and phosphorus removal mechanism. Membrane bioreactor is a newly developed wastewater treatment process and widely used in recent years. Combined with the actual operation process, researching and analysising the phosphate removal bacteria groups'structures would contribute a lot to the operating parameters'optimization.A molecular biologic technique of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyse the community structure of total bacteria in conventional sewage treatment system of A/O, traditional activated sludge aerobic treatment system, integrated MBR system and MBRof A/O. DNA in the brighter bands on total bacteria DGGE profile was recovered to clone and sequenced. The results showed that Aeromonas, Pseudomonas and Bacillus were the dominant specieses. In conventional sewage treatment systems, a variety of Aeromonas species occupied a significantly advantageous position because of their shorter generation cycles and less demand of nutrition. And in MBR systems, Pseudomonas and bacillus of long generation cycles were dominant species. With functions of aerobic denitrifying and denitrifying phosphorus removal, Pseudomonas owned a significant place in the integrated MBR system which contains high concentration of ammonia, and plays a very important role in nitrogen and phosphorus removal. High efficiencies of nitrogen and phosphorus removal and large amount of Pseudomonas indicated that in MBR systems the contradiction between the denitrification and phosphorus removal can be leveled out to a certain extent.Group structures of dominant phosphorus removing bacteria including Actinobacteria, Acidobacterium,α-proteobacteria andβ-proteobacteria in the above four sewage treatment systems were respectively studied. Many phosphorus removal specieses were separated, and the integrated MBR system had richest group diversity. Because of a high content of ammonia in influent, several denitrifying phosphorus removing specieses were domesticated in integrated MBR system, however,these bacteria was absent in other systems. The group structures and diversity of Acidobacterium andβ-proteobacteria varied greatly among four systems. It was rather this difference caused the different phosphorus removal efficiencies in the above four systems, and also indicated that these two types of bacteria played key roles in phosphorus removal.