Nitrogen removal efficiency analysis and microbial community characteristics of AAO sewage treatment system at low temperature
Temperature is the key factor to limit the microbial activity of sewage biological treatment,which will directly affect the efficiency of sewage treatment.For studying the pollution removal efficiency at low temperature conditions,this paper selected the AAO sewage treatment,which identifies the characteristics of microbial community structure at low temperature,explores the effects of different nitrification reflux ratio,carbon source type and sludge reflux ratio on the nitrogen removal performance of the system,and masters the coupling relationship between Extracellular Polymeric Substances(EPS)secretion and treatment conditions.The results show that the optimal treatment effect can be achieved by using complex carbon source,200％nitrification reflux ratio and 75％sludge reflux ratio at 12 ℃,which the average removal rates of COD,NH4+-N and TN can reach 87.26％,99.87％and 69.97％,respectively.And the effluent is far beyond the standard of grade I-A.In addition,PN is the largest contribution component of EPS which is mainly composed of TB layer,and the total amount of EPS and PS/PN are negatively correlated with the sludge reflux ratio.Using 16S rRNA gene amplicon sequencing analysis,the study found that Pseudomonas and Flavobacterium were the dominant bacteria in the system at low temperature.As a typical nitrite oxidizing bacteria,Nitrospira is inhibited.The process of partial nitrification coupled with heterotrophic nitrification and aerobic denitrification is obvious,resulting in greatly improved nitrogen removal performance.
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