Study On Simultaneous Denitrification And Desulfurization Of Bio-trickling Filter And Microbial Population Structure Under Intermediate Temperature And Aerobic Conditions

The NOx and SO₂ in the flue gas of coal-fired power plants lead to serious damage to the atmospheric environment,and the traditional industrial flue gas denitration and desulfurization process has the problems of high investment and construction costs,large floor space,and secondary pollution.Biological simultaneous denitrification and desulfurization technology has attracted more and more researchers'attention because of its low cost and environmental friendliness.Flue gas contains 3%-8%O₂,and the residual temperature after dedusting is still around50?.The objective of the current study is to evaluate the influence of O₂ on biological simultaneous denitration and desulfurization based on the environmental response characteristics of functional bacteria,liquid phase SO₄^2-/NO₃^-simultaneous biological reduction,and the simultaneous removal of NO/SO₂ in a biological filter tower?BTF?,and to clarify the microbial community dynamics responding to the O₂ concentration changes.?1?The response characteristics of the denitrification and desulfurization system under different environmental factors show that when C/N=15,C/S=3,DO<0.15mg/L and p H=7.5,the removal ability of SRB is the strongest and the accumulation of intermediate products is small.The S⁰ recovery rate is high,reaching a maximum of 60 mg/L.The functional bacteria in the denitrification and desulfurization system can still play a role under the medium temperature of 45?.?2?DO has a greater impact on the SO₄^2-/NO₃^-simultaneous biological reduction.When DO<0.15 mg/L,the NO₃^-removal rate is as high as 94%,there is no obvious intermediate product accumulation,but with the increase of O₂ concentration,the nitrogen removal performance decreases significantly.The activity of SRB is sensitive to the DO concentration,and the maximum removal rate in anoxic environment is 94.1%.The micro-oxygen conditions at DO=0.15 mg/L can promote SOB activity.Substrate kinetics experiments showed that SRB activity was inhibited by NO₃^-,and the final removal rate of SO₄^2-was negatively correlated with the initial NO₃^-concentration.?4?The denitration reaction in the BTF system is significantly affected by O₂.The highest NO removal rate was 96.5%at 5%O₂ concentration.Continued increase in O₂ concentration led to a decrease in NO removal rate and accumulation of intermediate products.The overall removal efficiency of SO₂ showed a decreasing trend with the increase of O₂,and the removal rate reached 93.6%under the condition of 3%O₂ concentration.The S⁰ increased first and then decreased with the O₂ concentration,and reached the highest recovery rate of 75.9%at the 5%O₂ concentration.The lower S^2-concentration at this stage can reduce the inhibition of denitrifying bacteria and indirectly promote the reduction of NO₃^-.Because micro-oxygen conditions can promote the conversion of SOB to S⁰,when the O₂ concentration is higher than8%,the S^2-and S0 concentrations both show a downward trend,and the S element exists in the system mainly in the form of SO₄^2-.?5?Microbial analysis showed that the microbial diversity was higher when the O₂concentration was 3%-5%.The dominant bacteria at the phylum level are Proteobacteria,Firmicutes,Bacteroidetes,etc.The dominant bacteria on the genus level are Thermomonas,Comamonas,and Pseudoxanthomonas.The microbial population structure is consistent with the NO and SO₂ removal rules.Pseudomonas,Paracoccus,Thiobacillus,etc.can simultaneously perform denitrification and sulfur oxidation functions.When the O₂concentration is not higher than 8%,Thiomonas is the dominant genus of SOB.At a concentration of 3%O₂,SRB has the highest content at the genus level,and the dominant bacteria is Desulfovibrio.Hierarchical cluster analysis shows that the differences in microbial communities have a clear correlation with O₂ as a whole.