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[Study on affecting factors of simultaneous nitrification and denitrification in moving-bed biofilm system].

The phenomenon of simultaneous nitrification and denitrification (SND) has taken place in moving-bed biofilm reactor (MBBR) steadily. The effect of C/N to denitrification effectiveness has been also studied in the experiment. The results of the treatment show that better denitrification efficiency could be obtained by increasing C/N ratio and the removal ratios of TN reached 92.9%. When C/N ratio is 12, the amplitude of TN removal ratio is not obvious. The effects of pH to ammonia nitrogen and TN removal ratio have been researched. The results show that the proper range of pH is 8.03-9.01 to removing ammonia nitrogen and the proper range of pH is 8.03-8.55 to TN efficiency. The experiment analyzed the influence of alkalinity and pH to denitrification efficiency, moreover, the relation of theoretical alkalinity and practical alkalinity has been studied. The results indicate that the influence of pH and alkalinity to removal efficiency of ammonia nitrogen and TN is low in SND, so does not need to adjust pH and increase alkalinity. The changes of pH and alkalinity during the reaction course were also investigated, and the result shows that pH can indicate the conversion process of nitrogen during a single representative period in SND.