Effect of Internal Recycle Ratio on Nitrogen Removal Efficiency in a Three-stage ANAMMOX Process for Treating Reject Water

摘要

ObjectivesIn order to improve the stability of the ANAMMOX process, a three-stage ANAMMOX process combined with denitritation/nitritation process was operated, and effect of internal recycle ratio on the nitrogen removal efficiency was investigated.MethodsFor the treatment of supernatant from anaerobic digester, a three-stage ANAMMOX process which combined as anoxic/oxic reactor and subsequent ANAMMOX reactor was installed. The reactor was designed with a working volume of 2.5 m3. The internal recycle ratio was considered as the main operating parameter, and the performance of nitrogen removal in the ANAMMOX process was evaluated.Results and DiscussionAs the internal recycle ratio was increased from 0 to 1.5Q, reduction of the nitrogen load increased to 23.5 ± 3.8%, and the nitrogen load reduced by internal recycle was 0.22 ± 0.04 kgN/m3/d. Since the ratio of NO2-N/NH3-N introduced in the ANAMMOX process is very important, considering this together, the most suitable internal recycle ratio was determined to be 1.5Q. As a result of introducing the effluent from the A/O process into the ANAMMOX process, the nitrogen removal rate could be stably maintained at 1.27 kg/m3/d.ConclusionsIn the ANAMMOX process in conjunction with the A/O process including internal recycle, the A/O process represented an effect of reducing the influent nitrogen load and nitrite concentration, and the ANAMMOX process was able to effectively remove residual nitrogen.