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Biotechnol Lett (2014) 36:547551 DOI 10.1007/s10529-013-1397-x
ORIGINAL RESEARCH PAPER
Nitrite (not free nitrous acid) is the main inhibitor of the anammox process at common pH conditions
D. Puyol J. M. Carvajal-Arroyo
R. Sierra-Alvarez J. A. Field
Received: 17 September 2013 / Accepted: 17 October 2013 / Published online: 30 October 2013 Springer Science+Business Media Dordrecht 2013
Abstract Nitrite is a substrate but also an inhibitor of anaerobic ammonium oxidation (anammox).There is currently no consensus on whether ionized nitrite (INi) or free nitrous acid (FNA) is the actual inhibitor of the process. The inhibition by INi and FNA on the anammox process has been analysed using a wide range of INi and FNA concentrations and by altering the pH and total nitrite conditions. The inhibitory impacts of both species were quantied through a rational inhibition equation, considering INi and FNA as substrate inhibitor and non-competitive inhibitor, respectively. Inhibitory constants were calculated with strong statistical support as 561 mg INi-N l-1 and
0.117 mg FNA-N l-1. Based on the model, INi is the main inhibiting species of the anammox process at
pH [ 7.1, which are the most common conditions occurring in eld applications of anammox.
Keywords Anaerobic ammonium oxidation
Anammox Free nitrous acid Inhibition
Kinetics Nitrite
Introduction
New bacterial processes of the nitrogen biogeocycle have led to innovative approaches to replace traditional bioprocesses for the bioremediation of nitrogen from wastewater (Francis et al. 2007) such as the conventional nitricationdenitrication process. The anaerobic ammonium oxidation (anammox) process has become one of the most promising alternatives for ammonium bioremediation (Kuenen 2008). This chemolithoautotrophic process typically involves the anaerobic oxidation of ammonium to N2 using nitrite as the nal electron acceptor. A molar ratio of ammonium/nitrite of around 1:1.3 is used during the anammox process. The higher demand for nitrite is due to some oxidation of nitrite to nitrate to support carbon xation (Strous et al. 1999). The kinetics of the anammox process has been explained by double substrate Monod kinetics. Anammox is also characterized by having a the slow growth rate with doubling times in the order of 7 d. The slow growth rate implies that technologies based on the anammox process are
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