Trace Dissolved Oxygen Removal Using a Hydrocyclone to Enhance Denitrification

Dissolved oxygen (DO) is entrained by mixed liquid recirculation (MLR) into the anoxic basin in the pre‐denitrification biological nitrogen removal (PDBNR) process and should be removed to enhance denitrification. A laboratory‐scale PDBNR reactor with an anoxic basin divided into two isometric components was built to investigate the effect of a hydrocyclone on DO removal from the MLR and the subsequent denitrification. The denitrification rate of the mixture of influent and hydrocyclone‐treated nitrified wastewater increased with increasing DO and was higher than that of the wastewater in a conventional anoxic component. More total nitrogen was removed in the anoxic component due to the application of the hydrocyclone in the MLR of a laboratory‐scale reactor and a full‐scale anoxic/aerobic reactor.