High NO and N2O accumulation during nitrite denitrification in lab-scale sequencing batch reactor: influencing factors and mechanism
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Nitrous oxide (N2O) accumulation in biological nitrogen removal has drawn much attention in recent years; however, nitric oxide (NO) accumulation in denitrification was rarely studied. In this study, NO and N2O accumulation during nitrite denitrification in a lab-scale sequencing batch reactor (SBR) were investigated. Results showed that low pH (< 7) and high influent loading (> 360:90) (COD:NO2−-N) caused serious NO and N2O accumulation. The maximal NO accumulation of 4.96 mg L−1 was observed at influent loading of 720:180 and the maximal N2O accumulation of 46.29 mg L−1 was found at pH of 6. The NO accumulation was far higher than the values reported in previous studies. In addition, the high NO accumulation could completely inhibit the activities of reductases involved in denitrification. High NO and N2O accumulation were mainly caused by significant free nitrous acid (FNA) and NO inhibition at low pH and high influent loading. There were significant differences on NO and N2O accumulation at different carbon to nitrogen (COD/N). Low COD/N (≤ 4) could mitigate NO accumulation, but led to high N2O accumulation. It is speculated that NO accumulation is related to the rapid denitrification with accumulated electron in anaerobic stage at high COD/N. N2O accumulation is attributed to intense electron competition at low COD/N. High dissolved oxygen (DO) of 4.04 mg L−1 was detected during NO detoxification in this experiment, which is speculated to be partly caused by NO dismutation.
KeywordsNitrite denitrification Nitric oxide Nitrous oxide NO inhibition NO dismutation
This work was financially supported by the National Natural Science Foundation of China (no. 51778057) and the Key Research and Development Program of Ningxia Hui Autonomous Region (no. 2019BFG02031).
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Conflict of interest
The authors declare that they have no conflict of interest.
- APHA (2005) Standard methods for the examination of water and wastewater. American Public Health Association (APHA), WashingtonGoogle Scholar
- Bergaust L, Mao Y, Bakken LR, Frostegard A (2010) Denitrification response patterns during the transition to anoxic respiration and posttranscriptional effects of suboptimal pH on nitrous oxide reductase in Paracoccus denitrificans. Appl Environ Microbiol 76:6387–6396. https://doi.org/10.1128/AEM.00608-10 CrossRefGoogle Scholar
- Brotto AC, Kligerman DC, Andrade SA, Ribeiro RP, Oliveira JL, Chandran K, de Mello WZ (2015) Factors controlling nitrous oxide emissions from a full-scale activated sludge system in the tropics. Environ Sci Pollut Res Int 22:11840–11849. https://doi.org/10.1007/s11356-015-4467-x CrossRefGoogle Scholar
- Li W, Zheng P, Guo J, Ji J, Zhang M, Zhang Z, Zhan E, Abbas G (2014) Characteristics of self-alkalization in high-rate denitrifying automatic circulation (DAC) reactor fed with methanol and sodium acetate. Bioresour Technol 154:44–50. https://doi.org/10.1016/j.biortech.2013.11.097 CrossRefGoogle Scholar
- Riya S, Zhou S, Kobara Y, Sagehashi M, Terada A, Hosomi M (2015) Influence of nitrogen loading and plant nitrogen assimilation on nitrogen leaching and N2O emission in forage rice paddy fields fertilized with liquid cattle waste. Environ Sci Pollut Res Int 22:5762–5771. https://doi.org/10.1007/s11356-014-3811-x CrossRefGoogle Scholar