Metabolic pathway of anaerobic ammonium oxidation on the basis of 15N studies in a fluidized bed reactor

Abstract

A novel metabolic pathway for anaerobic ammonium oxidation with nitrite as the electron acceptor has been elucidated using 15N-labelled nitrogen compounds. These experiments showed that ammonium was biologically oxidized with hydroxylamine as the most probable electron acceptor. The hydroxylamine itself is most likely derived from nitrite. Batch experiments in which ammonium was oxidized with hydroxylamine transiently accumulated hydrazine. The conversion of hydrazine to dinitrogen gas is postulated as the reaction generating electron equivalents for the reduction of nitrite to hydroxylamine. During the conversion of ammonium, a small amount of nitrate was formed from some of the nitrite. The addition of NH,OH to an operating fluidized bed system caused a stoichiometric increase in the ammonium conversion rate (1 mmol 1-1 h-l) and a decrease in the nitrate production rate (05 mmol I-' h-l). Addition of hydrazine also caused a decrease in nitrate production. On the basis of these findings, it is postulated that the oxidation of nitrite to nitrate could provide the anaerobic ammoniumoxidizing bacteria with the reducing equivalents necessary for CO, fixation.

S47 Study on Anaerobic Ammoniumoxidation (ANAMMOX) Sludge Immobilized in Different Gel Carriers and Its Nitrogen Removal Performance

“…In this process, NO 2 --N acts as the electron acceptor, and NH 4 + -N becomes oxidized to N 2 under anaerobic conditions [1]. Compared with the conventional nitrogen removal system (nitrification-denitrification [2]), the ANAM-MOX process has clear advantages: it does not require organic carbon and oxygen and produces less surplus sludge; these advantages all reduce operational cost [3][4][5].…”

Sensitive Method for the Oxidation-determination of Trace Hydroxylamine in Environmental Water Using Hypochlorite Followed by Gas Chromatography

“…NH2OH is also an intermediate in anaerobic ammonia oxidation (ANAMMOX). 13 By quantifying NH2OH, we can understand the ANAMMOX reaction in more detail.…”

“…In addition, hydrazine has attracted attention in recent years as an intermediate in anaerobic ammonia oxidation (ANAMMOX). 13 Nitrous oxide (N2O) is a greenhouse gas that is targeted for emission cuts under the Kyoto Protocol. Its global-warming potential is about 300-times greater than that of carbon dioxide (CO2).…”

Determination of Trace Hydrazine in Environmental Water Samples by in situ Solid Phase Extraction

“…In recent years, hydrazine has been reported as an intermediate formed during anaerobic ammonium oxidation (Anammox)-type denitrifying reaction. 2 Quantifying the hydrazine produced leads to a better understanding of the Anammox reaction. Hydrazine content is conventionally determined by voltammetry, 3 coulometry, 4 gas chromatography, 5 fluorescence spectroscopy, 6 spectrophotometry, 7,8 and titration.…”