Nitrogen removal via nitrite pathway and the related nitrous oxide emission during piggery wastewater treatment

Performance of partial nitrification (PN) via nitrite (NO2−) pathway and the related nitrous oxide (N2O) emission during piggery wastewater treatment was investigated. Dissolved oxygen (DO) concentration and aeration pattern were selected as operational parameters to investigate the possibility of NO2− accumulation without affecting the overall N removal. To obtain PN, aeration was done for a maximum of 3 h with a stopover of oxygenation, whenever DO concentration exceeds the threshold value of 2 mgO2 L−1. Ammonium (NH4+) consumption ended within 2 h of reaction, and at the end of NH4+ oxidation, about 70-80% of N was accumulated as NO2−. Using PN, an average N removal of 74-75% was observed, which is comparable to that of complete nitrification-denitrification process. Regulating the aeration pattern not only benefit to the N removal in piggery wastewater, but also favoured reduction of oxygen and organic matter requirements for nitrification and denitrification. N2O emission was not encouraged even with 70-80% of NO2− accumulation.