The Properties Of Removal Of Nitrogen And Phosphorus Of Improved A~2/o Process (a~2/o-mbnr Combined Process)

Traditional nitrogen and phosphorus removal processes exist many problems, as the sludge contradictions between phosphate-accumulating organisms and nitrification organisms, the competition of the carbon source between the denitrification organisms and the phosphate-accumulating organisms, which result in difficult balance between nitrogen and phosphorus removal. To solve these problems, designed A²/O-MBNR combined process, which used the phase separation cultivation of heterotrophic bacteria and autotrophic bacteria, shortened aeration time, and improved the nitrification and phosphorus removal effect. As the sludge retention time is as long as the traditional A²/O process, so this process is suitable for the transformation and upgrade of urban sewage treatment plant.Based on the previous study, the study program are: investigating the effect of SRT on the overall performance of process; investigating the TP removal is consistent as expected; investigating the effect of different carbon sources on nitrogen and phosphorus removal; investigating the overall operation of combined process under different conditions. The study results are as follows:The COD removal is great, the average removal rate is 87%. The degradation of the most organic matter already happened in the A²/O sector. The average TP removal rate is 86%, and the TP removal almost achieved in the activated sludge sector. The average NH ₄⁺- N removal rate achieved 96.8%, the high removal rate depended on the MBNR sector, in which most NH ₄⁺- N had been eliminated. Compared with traditional A²/O process, the aerobic nitrification occupied a small part of the total nitrification of the improved process, which achieved nitrification bacteria phase separation cultivation. The TN removal rate is 70%, and the reaction almost happened in A²/O sector.The effect of SRT on TP removal is obvious in the A²/O-MBBR combined process, TP removal was best when 3d SRT, which reduced about 10% when SRT shortened to 10d. For the nitrification effect is good of the MBNR sector, biofilm nitrification can improve the nitrification efficient, increase NH4+-N removal stability of the system, so SRT has little effect of the total nitrogen. The COD removal maintain at 85%.Water quality had great impact on the TP removal, and the effect on COD, NH4+-N, TN won't obvious. The water carbon of stage 2 is sewage joined acetate, the water carbon of stage 1 is sewage joined glucose, the TP removal rate of stage 2 improved 25% than stage 1. According to analysis this is for short HRT in anaerobic sector limited the full conversion of glucose to VFA, reduced the synthesis amount of PHB, lowered the TP release rate and removal rate. Then the glycogen can't contribute to the TP release.