Study On Start-up And Operation Conditions Of Partial Denitrifying Dephosphatation

The low carbon source is common in sewage treatment plants,which makes it difficult for the traditional nitrogen and phosphorus removal process of sewage treatment plants to meet the discharge standards.Partial denitrifying dephosphatation is a new method for nitrogen and phosphorus removal from low-carbon sewage,which can save carbon consumption and achieve simultaneous removal of nitrogen and phosphorus compared with traditional denitrification and phosphorus removal process.The partial denitrifying dephosphatation was initiated by two operation modes of anaerobic+aerobic/anoxic alternation and anaerobic+low dissolved oxygen.The partial denitrifying dephosphatation were operated in low C/N and C/P environments with 100 mg/L,25 mg/L,3.3 mg/L of COD,NH₄⁺-N and PO₄^3--P concentrations respectively.The difference between the two operation modes was analyzed by the transformation of pollutants,intracellular substances and the reaction rate of each strain.In addition,the effect of low intensityultrasoundirradiationonpartialdenitrifyingdephosphatationin anaerobic+aerobic/anoxic alternating operation was also explored.It was found that both anaerobic+aerobic/anoxic alternation and Anaerobic+low dissolved oxygen modes could successfully start partial denitrifying dephosphatation,which reached stability on 56 and 23 days respectively.After stable operation,the average PO₄^3--P of effluent was 0.27 mg/L and 0.19 mg/L,and the average TIN of effluent was 6.81 mg/L and8.21 mg/L,respectively.Although the treatment effects of the two operation modes were similar,the average PO₄^3--P of the two operation modes were 40.34 mg/L and 30.79 mg/L after anaerobic treatment,and theΔPHB of the cycle operation was+8.03 mg/g MLSS and-7.30 mg/g MLSS,respectively.The specific anoxic phosphorus release rates of NO₂^--N electron acceptor were 5.44 mg P/（h.g MLSS）and 4.51 mg P/（h.g MLSS）,respectively.These phenomena all indicated anaerobic release.These parameters indicate that the activity of phosphorus accumulating bacteria（PAO）is worse and the operating conditions is more unstable under the condition of anaerobic+low dissolved oxygen.After low density ultrasound irradiation,the effluent quality of the reactor stabilized was improved,PO₄^3--P and TIN were reduced by 53.3%and 36.8%,respectively,resulting in sludge reduction,and MLSS was reduced by 12.4%.The activity of NOB decreased under ultrasound irradiation,SNOR decreased by 51.11%.