Effects Of Tyical Microplastics On The Denitrification Characteristics And Denitrification Related Genes Of Aerobic Denitrifying Bacteria

The problem of water pollution has become the focus of hot discussion,and it is urgent to strengthen the research of sewage treatment technology.Nitrogen pollution and microplastic pollution caused a large amount of nitrogen and microplastics in urban sewage treatment plants.Aerobic denitrifying bacteria play an important role in the field of biological nitrogen removal,but the effect mechanism of microplastics on aerobic denitrifying bacteria remains unclear.Based on homemade enrichment of SBR aerobic denitrifying bacteria screening,probes into the typical microplastics(PS,PA)influence on aerobic denitrifying bacteria,at the same time the possible mechanisms were explored in terms of specific oxygen consumption rate,extracellular polymeric content,changes in microbial community structure,and changes in the abundance of denitrifying functional genes(nap A,nir S,cnor B,nos Z genes).The main innovation results are as follows:(1)Aeration and agitation were used to enrich aerobic denitrifying bacteria with high efficiency.Nitrogen,total nitrogen and total organic carbon were almost completely removed within 24h.The removal rate of ammonia nitrogen reached97.9%,and a small amount of nitrite was accumulated.The dominant species changed from Moraxellaceae to Rhodobacteraceae,and the microbial diversity decreased significantly.The change of microbial community promoted the proliferation of aerobic denitrifying bacteria.(2)After screening and purification of aerobic denitrifying bacteria,A11,C11,D11 and F11 strains were optimized.Two optimal strains of C11 and F11 were obtained,which grew well in aerobic environment.The removal efficiency of ammonia nitrogen and nitrate nitrogen was 93.9%and 96.0%,respectively,and the accumulation of nitrite was very small.It was identified as Pseudomonas?synxantha by its abundance at the species level.(3)Under the stress of two typical microplastics,the concentration of 100mg·L^-1 ammonia nitrogen can be completely removed,and both of them can promote the accumulation of nitrite to a certain extent.The accumulation of typical microplastics can inhibit the denitrification performance of aerobic denitrification bacteria,and PA has a greater inhibition effect on the aerobic denitrification.PA causes the increase of SOUR,and produces more EPS and SMP,which leads to the deterioration of water quality.After PS and PA acclimation,the relative abundance of Rhodospirillaceae and Rhodobacteraceae increased to 24.4%and 66.1%,respectively.The long-term stress of polyamide and polystyrene significantly changed the bacterial community structure at the family level.The nap A and nir S genes showed a trend of co-expression,and the gene abundance decreased by an order of magnitude,and the expression of both were inhibited.High-throughput sequencing revealed that the changes in the abundance and species of functional denitrifying microbial community were the main reasons for the changes in the denitrification performance of the SBR reactor.The research results of this paper have important reference and guiding significance for the application of aerobic denitrifying bacteria,biological denitrification and upgrading of urban sewage treatment plants.