The Study On Simultaneous Nitrification And Denitrification Via Nitrite

The water environment is polluted seriously in our country. Nitrogen is one of the main pollutions. The traditional biological denitrification process makes nitrification and denitrification occur in different units or in the same unit in sequence. So it is complex and hard to manage.Simultaneous nitrification and denitrification is a new biological denitrification process which was developed in the last few years. Not only this process may reduce the biomass production, shorten the nitrogen removal pathway, moreover offer the potential to save cost for a second (anoxic)tank, or at least reduce its size, if it can be ensured that a considerable amount of denitrification takes place together with nitrification in the aerated tank. If simultaneous nitrification and denitrification is accompanied by the inhibition of the second step of nitrification(oxidation of nitrite to nitrate), theoretically a saving of COD demand and oxygen demand could result. This is of particular interest when biologically removing nitrogen from wastewater with low COD: nitrogen ratio.The experiment was carried out to research on the synthetical wastewater with low COD:nitrogen ratio in Guangzhou in SBR. The factors were researched to achieve stable simultaneous nitrification and denitrification via nitrite. In the experiment, the simultaneous nitrification and denitrification via nitrite was achieved by controlling the sludge age. COD/N, pH in the raw wastewater and DO concentration was studied and the best operational process of nitrogen and organic matter removals was determinated. When the sludge age is about 11¹5d, COD/N is about 6.5, DO concentration is 0.3¹.0 mg·L^-1, pH in the mixed water is 7⁷.5, the removal rate of TN is the highest. It can reach to 81%～92%. The system was operated stably under the best operational process for 30d, the removal rate of TN is about 88%⁹3%.The results showed that simultaneous nitrification and denitrification via nitrite was stable by controlling optimal sludge age, COD/N, DO and pH.