Effect of dissolved oxygen on high C/N wastewater treatment in moving bed biofilm reactors based on heterotrophic nitrification and aerobic denitrification: Nitrogen removal performance and potential mechanisms

In this study, it was investigated the nitrogen removal (NR) performance and potential mechanism for high C/N wastewater treatment under different dissolved oxygen (DO) concentrations. The results showed that DO con-centration significantly affected the removal efficiency of total nitrogen (TN). When the initial DO increased from 0.5 to 1.5 mg/L, TN removal efficiency significantly increased from 65 % to 85 %. However, a further DO in-crease did not promote TN removal, and the NR was only 80 % with an initial DO concentration of 3.5 mg/L. The effect of DO concentration on NR was influenced by the combined action of functional bacteria and electron flow. Excessive DO concentration did not positively affect NR efficiency but promoted electron utilization and res-piratory proliferation. When the DO concentration was 1.5 mg/L, more electrons generated by sodium acetate metabolism were transferred to the aerobic denitrification process, compared to when the DO concentration was 3.5 mg/L.

Automated summary

This study investigated the influence of different dissolved oxygen concentrations on nitrogen removal in high C/N wastewater treatment. The results showed that dissolved oxygen concentration significantly affected the efficiency of total nitrogen removal. Within a certain range, increasing dissolved oxygen concentration improved the removal efficiency, but excessively high concentrations did not further promote nitrogen removal. The influence of dissolved oxygen concentration on nitrogen removal was influenced by the combined action of functional bacteria and electron flow.