Study On Mainstream Ammonia Nitrogen Enrichment-side Stream Partial Nitrification Anaerobic Ammonium Oxidation Process

In recent years,with the development of industrialization,the pollution problem caused by high ammonia nitrogen（NH₄⁺-N）wastewater has become increasingly serious.Excessive discharge of NH₄⁺-N will cause great harm to the ecological environment and the human body.It will not only promote the eutrophication of the water body,but also produce foul odors and cause obstacles to the water supply.During the 13th Five-Year Plan period,our country has put forward higher requirements for the discharge of ammonia nitrogen,and how to economically and efficiently remove ammonia nitrogen in sewage has become a research focus.Anammox process provides a new way for wastewater denitrification.Compared with the traditional denitrification process,anammox process can reduce the amount of organic carbon source added by 100%and the amount of aeration by 60%.The sludge production will also be reduced by 90%,which has a wide range of application prospects.Due to the limitation of the current anammox process,it is difficult to realize the application in mainstream sewage.The high cost of ammonia nitrogen adsorption material regeneration and the high concentration of ammonia nitrogen in the regenerated liquid need further treatment.This paper proposes mainstream ammonia nitrogen enrichment-side-stream partial nitrification anaerobic ammonium oxidation process.The optimization of the NH₄⁺-N adsorption material is mainly carried out,and the accumulation of the NH₄⁺-N concentration of the NH₄⁺-N adsorption material after multiple adsorption and regeneration of the NH₄⁺-N adsorption material with different Na Cl concentrations was also discussed.It was found that the accumulated NH₄⁺-N concentration of resin and zeolite after repeated adsorption and regeneration by 10 g/L Na Cl were 335 and 68.8 mg/L,respectively.When Ca²⁺and Mg²⁺exist,the NH₄⁺-N regenerated by 10 g/L Na Cl was only 233 mg/L.Ca²⁺and Mg²⁺will significantly affect the resin’s adsorption and regeneration on NH₄⁺-N.Therefore,when the resin was used to treat the actual wastewater,sodium carbonate and sodium hydroxide should be added to the regeneration solution regularly to remove the accumulated Ca²⁺and Mg²⁺.At the same time,the kinetic and thermodynamic characteristics of the resin before and after the long-term adsorption and regeneration operation in the presence of Ca²⁺and Mg²⁺were studied.It was found that the pseudo-first-order kinetic model has the highest degree of fitting to the resin adsorption process of NH₄⁺-N,indicating that the adsorption of NH₄⁺-N was mainly physical adsorption.The Langmuir adsorption isotherm was more suitable for describing the resin adsorption process of NH₄⁺-N,and the adsorption process is a single-layer adsorption.By gradually increasing the concentration of influent NH₄⁺-N and Na Cl,three sets of partial nitrification membrane bioreactors（PN-MBR）were operated in parallel to study the gradual domestication of sludge through different salt gradients to achieve the accumulation of nitrite（NO₂^--N）and the purpose of the molar ratio of NO₂^--N to NH₄⁺-N concentration in the effluent close to the theoretical ratio.It was found that stable NO₂^--N accumulation can be obtained under 10 g/L Na Cl.The nitrite accumulation rate（NAR）can reach91.1%,and the NH₄⁺-N removal rate（ARE）was 64.8%.The main genus of AOB was Nitrosomonas,and its relative abundance were 0.80%,16.1%and3.03%when the salt concentration were 0,5 and 10 g/L Na Cl.NOB was Nitrospira,and its relative abundance were 0.28%,2.23%and 3.18%when the salt concentration were 0,5 and 10 g/L Na Cl.Both the salt concentration and the salt gradients were crucial for the evolution of the microbial community to salt-tolerant bacteria.PN-MBR was rich in the partial nitrification of AOB（Nitrosomonas and norank＿f＿Nitrosomonadaceae）and An AOB（Candidatus＿Kuenenia and Candidatus＿Brocadia）.Different salt gradients produced different metabolic pathways even at the same salt concentration.The thesis studyed the influence of different Na Cl concentrations on the operating of PN-MBR and Anammox units to achieve the accumulation of NO₂^--N in the effluent of PN-MBR and the appropriate ratio of NO₂^--N to NH₄⁺-N.When the Na Cl concentration were 5,10,and 15 g/L,the molar ratio of NO₂^--N and NH₄⁺-N in the effluent of PN-MBR reached 2.00,1.61,and 0.55,respectively,indicating that 10 g/L Na Cl was more conducive to partial nitrification than 15 g/L.When the Na Cl concentration were 0,5,10 and 15g/L,therelative abundancesofNitrosomonasand norank＿f＿Nitrosomonadaceae were 0.29%,25.2%,18.7%,1.28%and 1.09%,0.02%,0.09%and 0.04%,respectively.Nitrospira belongs to NOB.When Na Cl increased from 0 g/L to 15 g/L,its relative abundance decreased from1.56%to 0%,and the salt concentration will differentiate between AOB and NOB.In the Anammox unit,the relative abundance of Planctomycetes at 0 g/L Na Cl was 42.9%.When the Na Cl concentration increased to 5,10,and 15 g/L,the relative abundance was 5.43%,2.25%,and 7.81%,respectively.Candidatus＿Kuenenia was a dominant genus,and its relative abundances at 0,5,10,and 15 g/L Na Cl were 40.2%,4.36%,0.17%,and 5.73%,respectively.The analysis of the nitrogen metabolism pathway showed that the NH₄⁺-N in the influent was oxidized to hydroxylamine under the action of the genes amo A,amo B,and amo C,and the hydroxylamine was further oxidized to NO₂^--N under the action of the gene hao.Then under the action of NO₂^--N oxidase,NO₃^--N was further produced in the PN-MBR.In the anammox unit,NO₂^--N generated NO under the action of NO₂^--N reductase.The genes involved in this process were mainly Nir K and Nir S.NO and NH₄⁺-N produced hydrazine under the action of hydrazine synthase.The genes involved in this process was mainly hzs.Under the action of the gene hdh,hydrazine produced N₂.