Nitrogen Removal Performance And Bacterial Community Structure Analysis Of VB₁₂ Production Wastewater Treated By Partial Nitritation-anammox Process

With the improvement of drug use structure and the increasing demand of vitamin drugs,vitamin B₁₂(VB₁₂)is a drug with lasting vitality in the market.In the production process of VB₁₂,wastewater with high ammonia nitrogen and low C/N ratio is produced.The traditional denitrification treatment process has low removal rate and high operating cost.The partial nitritation-anaerobic ammonia oxidation(PN/A)process is a new type of nitrogen removal process.Compared with the traditional denitrification process,it has the advantages of high removal rate,energy saving,and economy,but it is relatively difficult to startup and the operating conditions are harsh.This study successfully startuped the PN/A process,and studied the operating performance of the PN/A process to treat VB₁₂ production wastewater,and analyzed the changes in nitrogen during the operation,control conditions,nitrogen removal performance,and the microorganisms for nitrogen pollutant removal.Which provided technical support for the engineering application of PN/A process to treat VB₁₂production wastewater.The main contents of the research are as follows:(1)With synthetic wastewater as the feed water,the partial nitritation reactor was successfully startuped after 94 days,and the anaerobic ammonia oxidation(anammox)reactor was successfully startuped after 90 days.After the reactor was connected,the two-stage PN/A process startuped successfully after 23 days of operation.When the startup was successful,the influent NH₄⁺-N load in the partial nitrification reactor was0.90 kg/(m³·d),the ratio of the effluent NO₂^--N to NH₄⁺-N was 0.96,the NO₂^--N accumulation rate reached 93.0%,and The TN load of the influent water of the anammox reactor reached 0.90 kg/(m³·d),the TN removal efficiency reached 88.9%,the NH₄⁺-N removal rate reached 99.6%,and the NO₂^--N removal rate was 99.5%.(2)The VB₁₂ production wastewater diluted with clear water was used as the influent water of the two-stage PN/A process reactor successfully started,and the influent nitrogen load was gradually increased.When the influent NH₄⁺-N concentration was 705.4 mg/L,the effluent NH₄⁺-N,NO₂^--N and NO₃^--N concentrations were 19.1 mg/L,24.3 mg/L and 13.5 mg/L,respectively,and the influent TN load was 0.39 kg/(m³·d),the TN removal load reached 0.36 kg/(m³·d),and the TN removal efficiency was 91.0%.When the influent NH₄⁺-N concentration was increased to 1152.0 mg/L,the free ammonia concentration reached 201.4 mg/L,and partial nitritation was inhibited.After reducing the influent nitrogen load,the concentration of free ammonia was reduced and partial nitritation was restored,but the performance of anammox for nitrogen removal was poor.(3)Using high-throughput sequencing technology analyzed the microbial communities of the inoculated sludge(PN1 and PN2)of the partal nitritation reactor,the inoculated sludge(A1 and A2)of the anammox reactor,the sludge after the successful start-up of the two-stage PN/A process(PNS117 and AS113)and the sludge after the operation of the treatment of VB₁₂ production wastewater(PNE54 and AE54).Compared with inoculation sludge,the relative abundance of Proteobacteria and Bacteroidetes,which are related to NH₄⁺-N transformation,were increased in PNS117and PNE54 at the level of species in the partial nitritation reactor.At the genus level,Nitrosomonas increased by 2.4%and 5.3%in PNS117 and PNE54,respectively.In the anammox reactor,at the phylum level,the relative abundance of Planctomycetes where the anammox bacteria are located increased.At the genus level,anammox bacteria genus Candidatus.Kuenenia accounted for 0.0%and 0.3%in A1 and A2,AS113 and AE54 accounted for 2.2%and 5.2%,indicating that anammox bacteria were obtained domestication and enrichment in the operation process.The relative abundance of the two-stage PN/A process for nitrogen removal functional bacteria was increased,which ensured the stable operation of the two-stage PN/A process for the nitrogen removal of VB₁₂ production wastewater.