Effect of NH2OH and NO2-on N2O emission of anammox system
As a new biological nitrogen removal technology,anaerobic ammonium oxidation(anammox)is faced with N2O emissions,a greenhouse gas with high global warming potential.Hydroxylamine(NH2OH)and nitrite(NO2-)are key environmental factors affecting N2O emissions in the anammox system.Based on batch experiments,the effects of NH2OH and NO2- concentrations on N2O release in anammox process were investigated.The results showed that at low NO2- concentration(100 mg·L-1),the N2O emission increased with NH2OH concentration.However,at high NO2- concentration(300,500 mg·L-1),adding high concentrations of NH2OH(30,50 mg·L-1)could reduce N2O production.Microbial community analysis showed that at low NO2- concentration,adding NH2OH increased the relative abundance of heterotrophic bacteria while inhibited the growth of anammox bacteria.At high NO2- concentration,high doses of NH2OH promoted the growth of anammox bacteria and coexisting heterotrophic bacteria.Functional gene analysis showed that N2O emissions were regulated by nitrification,denitrification,and dissimilatory nitrate reduction to ammonium(DNRA)pathways and were positively correlated with the abundance of norB and nrfA genes(P＜0.05).Therefore,the N2O production in the anammox system is influenced by the combined effects of NO2 and NH2OH.When treating influent with high NO2- concentration,supplying an appropriate amount of NH2OH can reduce N2O emissions.On the other hand,in the case of insufficient nitrite,reducing NH2OH accumulation may mitigate N2O formation.This study provides a reference for operating the anammox process in a low-carbon-emission manner.
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