Nitrogen Removal Performance And Microbial Community Analysis Of Lincomycin Production Wastewater Treated By PN/A Process

The antibiotic production wastewater has strong microbial inhibition and high concentration of ammonia nitrogen and total nitrogen.The technical difficulty and economic cost of denitrification treatment of this kind of wastewater are very high,which brings great pressure to the production enterprises.Partial nitrification-Anammox（PN/A）process is a new type of denitrification process.Compared with the traditional denitrification treatment process,it has the advantages of high denitrification efficiency,energy saving and economy.It has great application potential in denitrification treatment.In this study,the laboratory-scale two-stage PN/A process plant was taken as the object,and the changes of operating parameters of the experimental plant in the process of rapid start-up of simulated wastewater and the operation performance of the actual lincomycin production wastewater denitrification process were studied.The microbial diversity and bacterial community structure changes in the experimental device were analyzed by 16S r RNA amplicon sequencing technology.The main results of this study are as follows:（1）In the start-up phase of the simulated wastewater,the PN reactor was inoculated with aerobic activated sludge from a sewage station of a pharmaceutical company in Ningxia,and the influent NH₄⁺-N loading rate（ANLR）was 0.42 kg NH₄⁺-N/（m3·d）after 73 days of commissioning and operation.The Nitrite accumulation rate（NAR）was 96.43%and the ammonia nitrogen removal efficiency（ANRE）was50.95%.At the same time,the ratio of NO₂^--N_ef/NH₄⁺-N_ef was 1.0.The Anammox reactor was inoculated with anaerobic granular sludge of UASB reactor in a sewage station of a starch plant in Kaifeng.After 73 days of commissioning and operation,the total nitrogen loading rate（TNLR）of the influent water was 0.13 kg N/（m3·d）,and the ANRE was 90.51%.Moreover,the total nitrogen removal efficiency（TNRE）reached90.63%,and the value of NO₂^--N_r/NH₄⁺-N_r and NO₃^--N_p/NH₄⁺-N_r were 1.14 and 0.09.（2）In the actual wastewater operation stage,the two-stage PN/A process was used to treat the effluent of the anaerobic reactor of a lincomycin production wastewater treatment station in an enterprise,and the total operation was 116 days.The influent NH₄⁺-N concentration of the PN reactor is about 400.0 mg/L,and the TNLR and the ANLR reach 0.73 kg N/（m³·d）and 0.70 kg NH₄⁺-N/（m³·d）,respectively.At the same time,the average values of ANRE and NAR are 52.31%and 97.40%,respectively.The average value of NO₂^--N_ef/NH₄⁺-N_ef is 1.09.The TNLR of Anammox reactor is 0.71kg N/（m3·d）,and the total nitrogen removal rate（TNRR）is 0.62 kg N/（m3·d）.Moreover,the average values of ANRE,NNRE and TNRE are 85.60%,98.21%and 87.96%,respectively.The average value of NO₂^--N_r/NH₄⁺-N_r and NO₃^--N_p/NH₄⁺-N_r are 1.31and 0.10,and the two-stage PN/A process has stable operation performance in treating lincomycin production wastewater.（3）In the two-stage PN/A process for the treatment of lincomycin production wastewater,the average COD concentration of the influent and effluent of the PN reactor were 1274.57 mg/L and 747.74 mg/L,respectively.And the average COD concentration of the effluent of the Anammox reactor was 650.57 mg/L.The PN reactor removed most of the COD in the wastewater,accounting for 84.43%of the total removal of COD,reducing the impact of organic matter on An AOB in the Anammox reactor.The degradable COD in the wastewater is utilized by denitrifying bacteria to cause denitrification.The synergistic effect of denitrification and anammox makes the TN removal rate stable at about 85%～87%,and the average NO₃^--N concentration in the effluent is 15.65 mg/L,far less than the theoretical concentration of NO₃^--N in the anammox reaction effluent.During the actual operation of wastewater,the concentrations of FA and FNA in the PN and Anammox reactors were all at low levels,which did not inhibit AOB and An AOB,and the two-stage PN/A process had ideal operating performance.（4）The results of 16S r RNA amplicon sequencing analysis showed that the microbial diversity at each stage changed and the similarity was low.Compared with the inoculated sludge,the relative abundance of Proteobacteria belonging to AOB in PN reactor increased from 17.00%to 63.38%,and the relative abundance of Planctomycetes belonging to An AOB in Anammox reactor increased from 1.66%to18.50%.In the late stage of lincomycin actual wastewater operation,the relative abundance of Proteobacteria in the PN reactor decreased to 58.85%,but it was still the dominant phyla in the reactor.The relative abundance of Planctomycetes in Anammox reactor decreased to 12.57%.The An AOB genera in Anammox reactor sludge were Candidatus＿Brocadia and Candidatus＿Kuenenia,their comprehensive relative abundance in the sludge increased from 0.03%to 1.68%and then decreased to 1.04%.Candidatus＿Kuenenia was the main An AOB genera in Anammox reactor.