Performance of heterotrophic partial denitrification under feast-famine condition of electron donor: A case study using acetate as external carbon source

Recently, the combination of anammox and post heterotrophic partial denitrification (nitrate to nitrite) was increasingly popular to treat anammox effluent with excessive nitrate, whereas achieving nitrite accumulation stably was a major bottleneck for post-denitrification. This work focused on the performance of heterotrophic partial denitrification under acetate feast-famine condition. The results showed that readily biodegradable COD to nitrate ( RBCOD / NO 3 - ) ratio of 2.5 facilitated an ideal nitrite accumulation ratio (NAR) of 71.7% under complete nitrate reduction. When RBCOD / NO 3 - ratio was below 3.5, in terms of efficiency and nitrite accumulation, higher NAR obtained during exogenous denitrification identified that the external acetate depletion was the optimal ending point of denitrification, which could be indicated by pH accurately. The indication of pH realized NAR of 60% ideally under batch-flow mode with RBCOD / NO 3 - ratio of 2.7, which might promote the scale-up of partial denitrification. Furthemore, alkaline environment (pH 9.0–9.6) repressed N2O emission even during endogenous denitrification.