Study On Adjustment Of Parameters And Technology Optimization Of Nitrogen And Phosphorus Removal Process In Nanjiao Wastewater Treatment Plant

With water eutrophication issue becoming increasingly prominent and the national andlocal effluent standards improving constantly, nitrogen and phosphorus removal has becomeone of the focuses of wastewater treatment research. As the main domestic sewage treatmentplant in Baotou city, Inner Mongolia Autonomous Region, Nanjiao wastewater treatmentplant has been adopting A2/O treatment process. However, there are some problems aboutthe plant, such as the inefficient dinitrification, the instability of the process. To solve theseissues, this paper is based on the optimizing of the actual project, concluding the process ofstart-up, adjusting the procedure parameters and optimizing the combined process researchof the A2/O-BAF process in the optimizing process after lab trilas.The main results are as follows:(1) The experiment using a250L anaerobic-anoxic-aerobic (A2/O) reactor withdomestic wastewater, culture and acclimated sludge to start the system. After stableoperation of the A2/O process, the effect of mixed reflux ratio, sludge return ratio, the sludgeage in the A2/O on the nitrogen and phosphate removal was discussed. The results showedthe optimal mixed reflux ratio of200%, the optimal sludge return ratio of75%, the bestsludge age of15d. At this point, the effluent quality was satisfactory with the first level Bcriteria specified in the Discharge Standard of Pollutants for Municipal WastewaterTreatment Plant (GB18918-2002).(2)The startup of the up-flow Biological Aerated Filter (BAF) with a new type ofpolyethylene SDC filtering material and denitrifying bacteria DNF409adopted compoundstartup with inoculums. The activated sludge was supplied by aeration tank of A2/O process.The result showed that compound startup can strengthen simultaneous nitrification anddenitrification and shorten the startup time, the biofilm formation of BAF reactor wereachieved after17days.(3) BAF has perfect treatment efficiency on sewage wastewater. The results showedthat when water temperature varied from17.4℃to22.2℃, at the quantity of12L/h, air/water ratio of3:1, after the biofilm formation, the average removal rates of COD, TN andNH4+-N were73.96%,70.36%and86.82%respectively, the effluent quality was satisfactorywith the first level A criteria specified in the Discharge Standard of Pollutants for MunicipalWastewater Treatment Plant (GB18918-2002).(4)Based on the stable operation parameters of A2/O process, the behavior of biologicalnitrogen and phosphorus removal in the A2/O-BAF combined system were investigated.After stable operation of the combined system, the COD, NH4+-N, TN and TP removalefficiency reached92.67%,94.62%,83.12%and92.55%respectively, the effluent qualitywas satisfactory with the first level A criteria specified in the Discharge Standard ofPollutants for Municipal Wastewater Treatment Plant (GB18918-2002). The study resultsclearly showed that COD, N and P can be simultaneously removed in the combined system,and it has a certain guiding meaning for upgrading reconstruction of Nanjiao wastewatertreatment plant.