Abstract
Nitrite (NO2-) substrate under certain conditions can cause failure of N-removal processes relying on anaerobic ammonium oxidizing (anammox) bacteria. Detoxification of NO2- can potentially be achieved by using exogenous nitrate (NO3-). In this work, continuous experiments in bioreactors with anammox bacteria closely related to "Candidatus Brocadia caroliniensis" were conducted to evaluate the effectiveness of short NO3- additions to reverse NO2- toxicity. The results show that a timely NO3- addition immediately after a NO2- stress event completely reversed the NO2- inhibition. This reversal occurs without NO3- being metabolized as evidence by lack of any 30N2 formation from 15N-NO3-. The maximum recovery rate was observed with 5 mM NO3- added for 3 days; however, slower but significant recovery was also observed with 5 mM NO3- for 1 day or 2 mM NO3- for 3 days. Without NO3- addition, long-term NO2- inhibition of anammox biomass resulted in irreversible damage of the cells. These results suggest that a short duration dose of NO3- to an anammox bioreactor can rapidly restore the activity of NO2--stressed anammox cells. On the basis of the results, a hypothesis about the detoxification mechanism related to narK genes in anammox bacteria is proposed and discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.