Effect of the Different COD/N Ratios on Multilevel Anaerobic/oxic Step-Feed Process for Integrated Removal of Carbon, Nitrogen and Phosphorus

Abstract

The present object of this stuidy is to investigate the effect of the different COD/N ratio on multilevel anaerobic/oxic (A/O) step-feed process for nitrogen and phosphorus removal used actual life sewage. The experiment designed the fluctuation of influent C/N ratio ranging from 4 to 8 and studied the variation rules of COD, NH3-N, NO3-N, NO2-N, total nitrogen, total phosphorus in the multilevel A/O process. Results showed when the influent C/N ratio was from 4 to 8, the C/N ratio on the removal efficiencies of COD and NH3-N was not significant, and COD average removal efficiency was 89.2 %, NH3-N average removal efficiency was 96.5 %. But the influent C/N ratio on denitrification and biological phosphorus removal effect was obvious, the total nitrogen removal rate increased from 44.7 to 68.9 to 87.3 % when the influent C/N ratio increased from 4 to 6 to 8. In the absence of specialized set of anaerobic zone condition, the total phosphorus removal efficiency had worked in certain. The total phosphorus removal rate increased from 58.7 to 64.7 to 71.8 % when the influent C/N ratio increased from 4 to 6 to 8.when the influent C/N ratio was 8, the effluent total phosphorus is 0.86 mg/L.

On the Rigid-Lid Hypothesis Application to the Flow Simulation of Step-Feed A/O Process

“…The step-feed A/O process, modified from the traditional A/O process, consists of one anaerobic reactor and several successive anoxic-oxic segments and the wastewater is delivered into the front of anaerobic and anoxic tanks. The removal rates of nitrogen and phosphorus is improved greatly due to the good growth conditions of phosphorus-accumulating bacteria, nitrifying and anti-nitrification bacteria [6][7][8]. The flow field simulation considering the movement of free surface is very difficult in current computer ability for such a complex step-feed A/O process with many reactors.…”