Research On Nitrogen Removal Mechanism Of Partial Nitrification Anammox Process Based On Quorum Sensing

The effects of organic carbon and microbial aggregation on partial nitrification anaerobic ammonia oxidation?PNA?were studied.The sequence batch biofilm reactor?SBBR?and the sequence batch activated sludge reactor?SBR?were used for PNA process.The effects of organic carbons on denitrification performance and functional bacteria in the two groups of reactors were studied.The differences of bacterial community structure in SBBR and SBR reactors were investigated,and the formation of extracellular polymeric substance?EPS?and the regulation mechanism of nitrogen metabolism were analyzed based on quorum sensing?QS?.After stabilization,the total nitrogen removal percentages of SBBR-N was higher than that of SBBR-CN,and the total nitrogen removal percentages of SBR-N was lower than that of SBR-CN.The nitrogen metabolism function bacteria activity was determined by batch experiments,anaerobic ammonia oxidation?Anammox?bacteria activity in the biofilm was significantly higher than that in activated sludge.Nitrite oxidizing bacteria?NOB?activity in biofilm was lower than that in activated sludge reactor which indicating biofilm compared with activated sludge can be effectively inhibit the NOB activity and protect the of Anammox bacteria activity.The Anammox bacteria activity and NOB activity in the reactors with additional organic carbon were lower than those in the reactors without organic carbon.The denitrifying bacteria activity was significantly higher than that in the reactor without organic carbon.Organic carbon inhibited the NOB activity and Anammox bacteria activity but promoted the denitrifying bacteria activity.Through the bacteria community analysis,it can be concluded that the heterotrophic bacteria accounts for a large proportion in the autotrophic nitrogen removal system.Compared with the activated sludge,the biofilm was not beneficial to the growth of ammonia oxidizing bacteria?AOB?and NOB,which was beneficial to the enrichment of Anammox bacteria.Organic carbon promoted the growth of denitrifying bacteria and inhibited the growth of AOB,NOB,and Anammox.The extraction EPS experiments showed that the concentration of tight extracellular polymeric substance?T-EPS?was highest,and protein was the main component in EPS.The concentration of T-EPS in the SBBR was much lower than that in the SBR.The concentration of T-EPS in the reactor with organic carbon adding was lower than that in the reactor without organic carbon adding.The Acyl homoserine lactones?AHLs?concentration of the signal molecules in each reactor was detected by LC-MS/MS technology.It was found that the signal molecules AHLs were mainly concentrated in the EPS phase and the biomass phase.The main components were N-octanoyl-L-homoserine lactone?C₈-HSL?,N-decanoyl-L-homoserine lactone(C₁₀-HSL)and N-dodecanoyl-L-homoserine lactone(C₁₂-HSL),and N-?3-oxodecanoyl?-L-homoserine lactone(3-oxo-C₁₀-HSL)was mainly in the EPS phase.The concentration of AHLs in SBBRs were lower than that in SBRs.The concentration of AHLs in the reactors with organic carbon adding were higher than in the reactor without organic carbon adding.Metagenomic analysis showed that the abundance of nitrification genes in SBBR-CN was higher than in SBBR-N,while the abundances of nitrate and nitrite reductase genes were lower.Contrary to the results of SBBRs,the abundance of nitrification genes in SBR-N were significantly higher than that in SBR-CN,while the abundance of denitrification genes were lower than that in SBR-CN.Similarly,the abundance of AHLs synthesis and sensing protein genes in SBBR-N were significantly higher than that in SBR-N,while the abundance of AHLs synthesis and sensing protein genes in SBBR-CN were significantly lower than that in SBR-CN.So organic carbon had different effects on the abundance of nitrogen metabolic function genes and the abundance of QS genes in activated sludge and biofilm system.In SBBR-N,except algB and algA,the alginate synthesis gene abundance was higher than that in SBBR-CN,and the alginate synthesis gene abundance in SBR-CN was higher than that in SBR-N.So the organic carbon had different effects on alginate synthesis in activated sludge and biofilm system.The main carriers of alginate synthesis genes are functional bacteria involved in the nitrogen metabolic pathway.The abundance of hisD,trpA and serB genes associated with amino acid synthesis in SBBR-CN were higher than that in SBBR-N.The abundance of above several genes in SBR-CN was lower than that in SBR-N.The major carriers of amino acid synthesis genes are related functional bacteria involved in nitrogen metabolism.