Research On Nitrogen Removal Of Wastewater With Low Concentration And Different C/N By A/O/N Process

According to traditional denitrification theory, while influent C/N ratio is much too high in biological nitrogen removal process, autotrophic organism under the existence of a lot of organic substance is less competitive than heterotrophic bacteria in the scrambling for oxygen and nutrition, which makes heterotrophic bacteria in the ascendant and ammonia not translated into nitrite and nitrate very well , so that denitrification efficiency reduces; if influent C/N ratio is too low and nitration reaction time lasts too long, this may cause low denitrification efficiency because of lacking of enough organic substance as electron offerings. Hereby, the experimental investigation on A/O/N process was done for wastewater with low concentration and different C/N ratio.The results show that thanks to their living in respective fitting environment in separate reactors, there is no the competition between heterotrophic bacteria and autotrophic nitrate bacteria, the nitration efficiency was not influenced by influent C/N ratio, the best nitration can be obtained when influent C/N ratio is 5.1, and nitration efficiency and denitrification efficiency cannot be influenced by the increasing C/N ratio; in the A/O/N process, when influent C/N ratio is between 2.2 and 9.8, the TN removal efficiency changes regularly along with the C/N ratio.Comparing the research results of A/O/N process to those of A/O process, the denitrification effect of A/O/N process is obviously preponderant. The best influent C/N ratio of A/O process is 7.7, and the nitration efficiency decreases with the increasing influent C/N ratio, of which there is a good linear relationship. The nitration efficiency of A/O/N process is not influenced by influent C/N ratio, and the nitrification efficiency of A/O/N process system still amounts to 95% with high influent C/N ratio.The result of the research on denitrification mechanism of A/O/N process shows that nitrification-denitrification via nitrite reaction take place in the denitrification process of A/O/N process. The denitrification dynamics mode of A/O/N process is discussed primary in the paper.