Simultaneous Treatment Of Wastewater And Flue Gas Denitration Process By Anammox-denitrification Biological Trickling Filter

NO_X pollution have gradually become one of primary environmental problems that people pay more and more attention to.Although the traditional flue gas desulfurization and denitration processes tend to be mature,it still has problems such as high cost,secondary pollution,adsorbent regeneration and so on.Biological desulfurization and denitrification can make up for the shortcomings of traditional physicochemical desulfurization and denitrification,and it is a promising exploration of flue gas terminal treatment with the advantages of mild reaction conditions,no catalyst and environmental friendliness.Based on the principle of metabolism using NO as substrate of anaerobic ammonia oxidation bacteria（An AOB）and denitrification bacteria（DNB）and anaerobic ammonia oxidation（Anammox）coupled denitrification（DN）,this study proposes to establish an Anammox coupled denitrification biological trickling filter（DEAMX-BTF）to remove NOx from coal-fired flue gas,by using organic matter（glucose,starch）and NH₄⁺-N of urban sewage components.This study mainly investigated the effects of carbon nitrogen ratio of spray liquid,nitrogen composition of spray liquid,NO_X concentration and SO₂addition on denitrification performance,NO_X removal and microbial community structure of DEAMX-BTF system under low oxygen conditions.The main results are as follows:（1）Start-up performance and control strategy of Anammox biological trickling filterAt the initial stage of start-up of Anammox biological trickling filter,suspended An AOB sludge was used as inoculated sludge,NH₄⁺-N spray concentration is 50mg/L,NO₂^--N concentration is 66 mg/L.Reduced the total nitrogen load from 0.58Kg N·m^-3·d^-1 to 0.29 Kg N·m^-3·d^-1,the total nitrogen removal rate of the system increased from 5%to 61.0%.After the simultaneous removal of NH₄⁺-N and NO₂^--N,shorten the hydraulic retention time of spray liquid of Anammox biological trickling filter,the total nitrogen load was increased to 0.58 Kg N·m^-3·d^-1,the total nitrogen removal rate of the system was further-improved from 61.0%to 77.6%,the total nitrogen removal load was increased to 0.5 Kg N·m^-3·d^-1,achieving the startup of Anammox biological trickling filter within 21 days.（2）Effect of carbon nitrogen ratio on nitrogen removal efficiency and microbial community structure of Anammox trickling filter under low oxygen conditionWith the concentration of 2%O₂,increasing the C/TN of spray liquid from 0.5to 1.5,the NH₄⁺-N removal rate of DEAMX-BTF system was increased from 94.9%to 96.0%,the total nitrogen removal rate was increased from 64.6%to 72.9%and the COD removal rate was increased from 80%to 94.8%;Increasing the C/TN from 1.5to 2,the total nitrogen removal rate did not increase significantly;The addition of 2%O₂ promoted the nitrification process of the system,resulting in the decrease of the total nitrogen removal rate.Gradually increasing the C/TN of the spray liquid to 1.5,the total nitrogen removal rate of the system was increased to a close rate（72.9%to77.6%）of the stage without adding 2%O₂,indicating that the Anammox coupling DN under appropriate C/TN can alleviate the adverse impact of O₂ on the total nitrogen removal of the system to a certain extent.According to the experimental analysis of sludge offsite activity,increasing C/TN from 1.5 to 2,the contribution of Anammox to denitrification decreased from 65.4%to 58.0%.After adding denitrifying sludge,the average total nitrogen removal rate of the system increased by9.4%and reached 72.6%±4.09%.The change of C/TN and bioaugmentation will change the bacterial community structure of BTF system and cause the change of enzyme expression at molecular level on KEGG pathway.When C/TN increased to 2,enzymes related to nitrification,denitrification,anaerobic ammonia oxidation and other metabolic pathways were up-regulated.The dominant bacteria at this stage are g＿＿unclassified＿＿f＿＿Comamonadaceae,g＿＿Olb12 and g＿＿Bdellovibrio.The enzymes related to nitrification and denitrification metabolic pathways were down-regulated after adding denitrifying sludge.The dominant bacteria at this stage are f＿＿norank＿＿o＿＿DS-100,g＿＿norank＿＿f＿＿Akyh767 and g＿＿Bacillus.The g＿＿Candidatus＿＿Brocadia is the only An AOB in the system.（3）Effect of spray liquid nitrogen composition on denitrification performance and bacterial community structure of DEAMX-BTF systemWhen the inlet gas contains 200 ppm NO_X,reducing the ratio of NO₂^--N/NH₄⁺-N in the spray liquid from 1.32 to 0.45,the average NH₄⁺-N removal rate of the system was reduced from 98.6%to 81.7%,the total nitrogen removal rate was reduced from69.5%to 51.6%,the average O₂ consumption of the system was increased from 0.58%to 0.95%,the NO_X removal efficiency was stable to 98.1±1.0%.After reducing the ratio of influent NO₂^--N,some key enzymes in the nitrification pathway,anaerobic ammonia oxidation pathway,dissimilatory nitrate reduction pathway and denitrification pathway of KEGG pathway were up-regulated to varying degrees,and the microbial community structure of DEAMX-BTF system was changed.The dominant bacteria at this stage are g＿unclassified＿＿f＿＿Comamonadaceae、g＿＿norank＿＿f＿＿AKYH767,g＿＿Cloacibacterium.The g＿＿Candidatus＿＿Brocadia is the only Anammox bacterium in the system.（4）Effect of inlet NO_X concentration and SO₂ on denitrification performance and bacterial community structure of DEAMX-BTF systemIncreasing the NO_X concentration from 200 ppm to 800 ppm in the inlet gas,the total nitrogen removal rate of the system was increased from 62.1%to 71.0%,and the average NO_X purification rate was stable at 98.7%;After adding 1000 ppm SO₂ to the inlet gas,the average total nitrogen removal rate of the system was increased to 75.0±5.2%and the SO₂ purification rate was 100%.The data show that the DEAMX-BTF system has good performance of gas-water coordinated denitrification and sulfur resistance.The change of inlet gas composition caused the change of bacterial community structure in DEAMX-BTF system and the up-regulation and down-regulation of enzyme expression at molecular level in KEGG pathway.The dominant bacteria in the low concentration NO_X（200 ppm）stage are g＿＿norank＿＿f＿＿norank＿o＿＿norank＿＿c＿＿SJA-28,g＿＿norank＿＿f＿＿AKYH767,g＿＿norank＿＿f＿＿norank＿＿o＿＿Kapabacteriales.The dominant bacteria at high NO_X concentration（500 ppm～800ppm）stage are g＿＿Gordonia,g＿＿norank＿＿f＿＿norank＿＿o＿＿norank＿＿c＿＿SJA-28,g＿＿norank＿＿f＿＿norank＿＿o＿＿Candidatus＿Falkowbacteria.The g＿＿Candidatus＿Brocadia is the only An AOB in the system.