The effect of oxygen supply on nitrogen removal via nitrite using stored substrate (PHB) as the electron donor in SBRs

This study investigated the effect of oxygen supply on nitrogen removal performance, by applying different oxygen supplies to four SBRs during aeration. That resulted in four different volumetric oxygen transfer coefficients (KLa), which were 3.64 h−1, 10.56 h−1, 16.82 h−1, 28.17 h−1. The research showed that the overall specific nitrogen removal load increased from 0.64 to 3.03 mmolN CmolX−1 h−1, with the increased oxygen supply. Total nitrogen removal reaching above 97%, even with KLa of 10.56 h−1. When oxygen supply increased (KLa increased from 3.64 to 16.82 h−1), the percent of SND decreased, while the rate of SND increased. However, they both decreased when oxygen supply continued to increase (KLa increased to 28.17 h−1). Besides, stronger oxygen supply in aeration preserved more PHB at the start of anoxic stage, which facilitated endogenous denitritation rate from 0.58 to 3.68 mmolN CmolX−1 h−1. In summary, stronger oxygen supply benefits nitrogen removal performance.