such as landfill leachate or supernatant of anaerobic digestion, the most common control way to achieve nitrogen removal via nitrite is to maintain high free ammonia (FA) concentration in the mixed liquor.
Sequencing batch reactors (SBRs) are usually applied for the nitrogen removal via nitrite taking advantage of their flexibility to operate at multiple aerobic and anoxic periods with low space
requirement (Ge et al., 2015).