Characteristics Of Simultaneous Nitrogen And Phosphorus Removal By DNAPR Coupled With Anammox Process

In recent years,partical denitrification（PD,NO₃^--N→NO₂^--N）has become increasingly popular.Denitrification Phosphorus Removal（DPR）,as a representative process for biological phosphorus removal of sewage,has attracted considerable attention due to its advantages of"simultaneous use of carbon sources",no need for aeration,and low sludge output.PD was coupled with DPR,NO₃^--N reduction could be carried out under the synergistic effect of denitrifying phosphorus accumulating organisms（DPAOs）and denitrifying glycogen accumulating organisms（DGAOs）,NO₂^--N accumulation and PO₄^3--P removal could be realized at the same time,which provides a new idea of combined anaerobic ammonium oxidation（Anammox）and phosphorus removal process.Based on this,this article explored the feasibility of PD-DPR coupled with Anammox to treat municipal sewage and high nitrate wastewater to achieve simultaneous nitrogen and phosphorus removal,investigated the start-up and optimizing operating characteristics of the PD-DPR system.In addition,a new type of denitrification nitrous accumulation and phosphorus removal system（DNAPR）was constructed by changing the operating volume,its startup characteristics,denitrification and phosphorus removal performance,and flora structure characteristics were investigated.At the same time,the operation mechanism of denitrification nitrous accumulation and phosphorus removal+anaerobic ammonia oxidation（DNAPR+Aanmmox）process was studied,its operational feasibility and characteristics of nitrogen and phosphorus removal were investigated to provide experimental data and theoretical support for the nitrogen and phosphorus removal of municipal wastewater and high nitrate wastewater by DNAPR+Anammox.The main research contents and achievements were as follows:（1）The start-up and optimal operation characteristics of PD-DPR system were investigated.In an anaerobic-anoxic-aerobic sequencing batch reactor（SBR）,the partial denitrification process（PD,NO₃^--N→NO₂^--N）was coupled with the denitrifying phosphorus removal process（DPR）in order to treat simulated municipal wastewater and high nitrate wastewater.The characteristics of nitrite accumulation and phosphorus removal in PD-DPR were investigated.The results showed that after 140 days,the conversion rate of NO₃^--N→NO₂^--N（NTR）was 80.1%,and the removal rate of PO₄^3--P was 97.64%.In the anaerobic stage（180 min）,the organic carbon source of wastewater was fully utilized by glycogen accumulating organisms（GAOs）and phosphorus accumulating organisms（PAOs）to transform them into internal carbon source;In the anoxic stage（150 min）,denitrifying glycogen accumulating organisms（DGAOs）and denitrifying ordinary heterotrophic organisms（DOHOs）carried out endogenous and exogenous partial denitrification respectively to achieve stable accumulation of NO₂^--N,while denitrifying phosphorus accumulating organisms（DPAOs）carried out efficient denitrifying phosphorus uptake.In the aerobic stage（10 min）,PAOs could absorb excessive phosphorus without nitrification,which improves the phosphorus removal performance of the system.The effluent NO₂^--N/NH₄⁺-N ratio is 1.31∶1（close to the theoretical value of anammox process of 1.32∶1）,PO₄^3--P concentration was 0.30 mg/L,COD concentration was 12.94 mg/L.The effluent quality could meet the demand of deep nitrogen removal coupled with anammox process.（2）A new denitrifying nitrite accumulation and phosphorus removal（DNAPR）system was constructed.Based on the study of the start-up and optimization characteristics of PD-DPR system,a new type of anaerobic-anoxic-aerobic denitrification nitrite accumulation phosphorus removal（DNAPR）process was constructed by changing the operation volume.The simultaneous treatment of municipal wastewater and NO₃^--N wastewater（volume ratio is 5:1）were realized.In the DNAPR,the conversion rate of nitrate to nitrite（78.35%）and the phosphorus removal rate（98.34%）achieved the expected stable effect by adjusting the influent composition,discharging the anaerobic end supernatant,shortening anoxic time and increasing short-time aeration.After 141days of operation,the effluent COD was 16.63 mg/L,NO₂^--N was 54.16 mg/L,PO₄^3--P was 0.37 mg/L,NO₂^--N/NH₄⁺-N was 1.3.Microbiological analysis showed that Thauera（34.9%）and unclassified＿f＿Rhodobacteraceae（6.79%）were functional bacterias of DNAPR.（3）The feasibility of DNAPR+Anammox for nitrogen and phosphorus removal were investigated.In order to explore the effect of low substrate concentration effect of anammox,influent volume was increased,the operation characteristics of anammox under the condition of low substrate concentration were investigated.The results investigated that the reduction of substrate concentration had no effect on the nitrogen removal performance of Anammox.The effluent NH₄⁺-N and NO₂^--N concentrations could be maintained at 0.46 and 0.63 mg/L,and NO₂^--N/NH₄⁺-N was as high as 1.32.At the same time,in order to explore the feasibility of DNAPR+Anammox coupling process to achieve simultaneous nitrogen and phosphorus removal,the long-term operation test of DNAPR+Anammox coupling process was carried out.After 73days of operation,the TN removal rate and PO₄^3--P removal rate reached 89%and 99%,respectively,the effluent COD was 16.67 mg/L.The results showed that the DNAPR+Anammox could be used for advanced treatment of municipal wastewater.