Approach to enhancing nitrogen removal performance with fluctuation of influent in an oxidation ditch system

This study investigated the influence of the daily fluctuation of influent (IF) on nitrogen removal performance in oxidation ditch. The feasible velocity and dissolved oxygen conditions for simultaneous nitrification–denitrification (SND) were examined by conducting a trial experiment. The proportion of aerobic zone fraction (PAZF) was evaluated as a key control factor affecting the SND in the ditch. An innovative PAZF control technology was proposed to optimize the aeration conditions and the external recirculation rate of activated sludge in response to IF. The results indicated that the effluent quality effectively improved using the PAZF control technology. The effluent adhered to the new discharge standards for China: NH3–N < 5 and TN < 15 mg/L. The control technology was easily implemented by programmable logic controller at a wastewater treatment plant.

► Influence of influent fluctuation on operational parameters of oxidation ditch.
► Proportion of aerobic zone fraction (PAZF) was adopted as a new control factor of SND.
► Proposed an innovative control technology to enhance the nitrogen removal.
► Improve the effluent of oxidation ditch against influent fluctuation.