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Nitric Oxide For Anammox Recovery In Nitrite-inhibited Deammonificatio

Congress: 2015
Author(s): Ivar Zekker (Tartu), Ivar Zekker
Univ Tartu1

Keyword(s): Sub-theme 1: Water supply and demand,
Abstract IVAR ZEKKERa*, ERGO RIKMANNa, TOOMAS TENNOa, LIIS LOORITSb, KRISTEL KROONa, HANNU FRITZEc, TERO TUOMIVIRTAc, PRIIT VABAMÄEa, MARKUS RAUDKIVIa AND TAAVO TENNOa a Institute of Chemistry, University of Tartu, 14a Ravila St., 50411 Tartu, Estonia. E-mail. (Ivar.Zekker@ut.ee) b Tallinn University of Technology, Ehitajate St. 5, 19086 Tallinn. E-mail. (Liis.Loorits@ttu.ee) c Finnish Forest Research Institute, P.O. Box 18, 01301 Vantaa, Finland Key words: deammonification, digester, intermittent aeration, nitrite inhibition INTRODUCTION In a wastewater treatment plant nitrogen-rich wastewaters treatment by nitrification-denitrification is costly due to need for extensive aeration and need for organic C source. Partial nitrification coupled with anaerobic ammonium oxidation (anammox) process enables to save from aeration and organic C. Nitric oxide (NO) formed by nitrogen converting microorganisms (e.g. anammox) is a reactive and toxic compound to many organisms- for nitrifiers, denitrifiers even at a few µM concentrations, also contributing to air pollution. However, anammox process is accelerated by NO (Kartal et al., 2010) being sensitible to elevated substrate (nitrite) concentrations. The activity decreased by nitrite inhibition can be restored by adding trace amounts of the anammox intermediate NO. In current research there was aimed to determine the effect of specific amount of the anammox intermediate- NO on deammonifying biofilm at the presence of increased levels of nitrite. MATERIALS AND METHODS To establish the correlation between nitrogen removal rate and effect of NO at inhibitory nitrite concentration- a series of batch-scale experiments with biofilm carriers from MBBR were performed. 200 biofilm carriers with biofilm total suspended solids of 3.74 (± 0.25) mg carrier-1 taken from a lab-scale moving bed biofilm reactor (MBBR) were incubated at temperatuur 25 (± 0.5) °C for 6 h measuring N forms concentrations after every 2 h. Also, the emitted nitrogen gas's pressure measurements were performed by Oxitop® system. Total nitrogen (TN) removal rate of 20 L lab-scale MBBR operated at 22 (± 0.5)° C by nitritation-anammox process was 1 kg N m-3 d-1 (Zekker et al., 2013). MBBR system's optimal nitrite concentration determined was 40 mg NO2--N L-1 and the fractional nitrite inhibition (>30% activity decrease) concentration was determined at concentrations above 60 mg NO2--N L-1. The results showed that nitric oxide in amount of 36.8 mg NO-N L-1 had the highest effect on anammox activity recovery on the MBBR biofilm carriers. The nitrogen removal rate was increased about 49% in comparison with experiments performed at nitrite concentration of 60 mg NO2--N L-1 without NO addition. The results of emitted N2 pressure measurements performed by Oxitop® system confirmed that the anammox mass balance was valid as nitrogen removal rate measured by sum of liquid phase components (NH4-, NO2-, NO3-, N2H4 and NH2OH) decrease in time equalled to that measured by gas pressure. Quantitative 16S rRNA analysis showed presence of 3.5×106 anammox gene copies µL-1 during experiments showing no decrease in anammox quantities when using NO. Overall, nitric oxide at a certain concentration of 36.8 mg NO-N L-1 was determined to have accelerating effect on anammox process, enabling biomass recovery even at inhibiting nitrite concentrations. Acknowledgements The study was supported by the projects (SF0180135s08), (SLOTI08262), (SLOKT11027T), (SLOKT11119) and (1.2.0401.09-0079 in Estonia). References Kartal, B; Tan, NCG; Van de Biezen, E; Kampschreur, MJ; Van Loosdrecht, MCM,Jetten, MSM, 2010. Effect of Nitric Oxide on Anammox Bacteria. Applied and environmental microbiology, 76 (18), 6304–6306. Zekker, I, Rikmann, E,Tenno, T., Kroon, K., Vabamäe, P, Salo, E., Loorits, L., Rubin, S., Vlaeminck, S., Tenno , T. 2013. Deammonification process start-up after enrichment of anammox microorganisms from reject water in a moving-bed biofilm reactor, Environmental Technology, 34 (23), 3095-3101.
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