Study On Influence Factors And Operating Characteristic Of Nitrogen Removal In Anoxic/Aerobic Membrane Bioreactor

As the main nutrient elements of aquatic plant and microorganism, excessive nitrogen would cause eutrophication, and produce toxicity to various aquatic species. Even more, excessive nitrate accumulation in the body can induce cancer and harm to human health.On the basis of the principle of traditional biological nitrogen removal and the advantages of membrane bioreactor features, an anoxic/aerobic membrane bioreactor was chosen to treat schoolyard domestic wastewater in this topic. The influence of operating parameters to the effect of nitrogen removal and the denitrification mechanism were investaged in this study.Firstly, the removal efficiency of pollutant in this process were investigated. The results indicated that this system has a better pollutant removal effect on COD and TN, but TP removal efficiency was not lower. Secondly, the effect of internal recycle ratio (IR), sludge retention time(SRT), and the ratio of carbon to nitrogen(C/N) on nitrogen removal efficiency and the sludge properties were mianly studied. The results indicated that the chage of IR has a less effect on the removal of ammonia nitrogen, its removal efficiency was basically maintaince above 91%. Long SRT and high activated sludge concentration can keep the amount of microorganisms, the nitrogen removal rate was better. But the MLVSS/MLSS was decresead with the increase of SRT. With the increase of SRT, SV₃₀ was increased by power function y=16.87x^0.27, and SVI was decreased by polynomial second power equation y=100.8-0.421x+0.009x². The aerobic denitrification rate was better with the increase of C/N, While the ammonia nitrogen removal rate was not obciously affected by C/N. The optimal process operation was under the IR of 300%, SRT of 30d and C/N of 8.0.During the experimental research, it was found that the activated sludge has a good nitrification and denitrification activity in the optimum situation. The specific nitrification and denitrification rate were 7.61mgNH₄⁺-N/g MLVSS·hå'Œ5.42mgNO₃^--N/ gMLVSS·h respectively. The dominant species of nitrification was ammonia-oxidizing bacteria, its number was 9.5×10⁷cfu/mL. Using PCR-DGGE technique, the community structure and characteristic of resources diversity of denitrification bacreria and ammonia-oxidizing bacteria in A/O-MBR reactor were studied. Results showed that the microbial community was very abundant in this reactor, there are many community strain in anoxic zone and aerobic zone. In the finality, according to the analysis on the sludge layer composition of membrane surface through SEM image, the most appropriate cleaning method was water cleaning, picking, and alkali washing, the recovery rate of membrane specific flux was 94.3% after membrane cleaning.