Effect of Different Influent Flow Distribution Ratios on Multistage A/O Process for Removal of Carbon and Nitrogen

Three-stage step-feed A/O system was applied to treat sewage with low carbon source. The removal of organic matter, nitrification and denitrification removal efficiency under different influent flow rate distribution ratios were discussed. It was showed that different flow distribution ratios (4: 3: 3; 5: 3: 2; 6: 3: 1) had a little effect on organic matter removal and nitrification efficiency, COD, NH3-N of effluent were below 30 and 1.0 mg/L, respectively, by monitoring water quality along the reactor, but denitrification efficiency was considerably affected. When flow distribution ratio was 5: 3: 2, carbon source of sewage was effectively used and the system achieved the optimum efficiency of nitrification. When flow distribution ratio was 5: 3: 2, the effluent total nitrogen was 5.7 mg/L and removal ratio of total nitrogen was 82.9 %, which was better than the nitrogen removal efficiency under the flow distribution ratios of 6: 3: 1 and 4: 3: 3. In summary, the step-feed system is superior to single point feed system in the aspect of effectively usage of carbon sources and energy saving.