Study of control strategy and simulation in anoxic-oxic nitrogen removal process

摘要

The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic(A/O) process with low carbon: nitrogen(C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite(NOx-N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx-N concentration in the anoxic zone( S_(NO)) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen(TN) could not be largely improved by double dosage of carbon source when S_(NO) reached about 2 mg/L. Through keeping S_(NO) at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No. 1 (ASM No.l), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-foward PI controller had better control effects due to its consideration of influent disturbances.