Anaerobic ammonium oxidation by Nitrosomonas spp. and anammox bacteria in a sequencing batch reactor

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2008.03.003 Byline: Pongsak (Lek) Noophan (a), Siriporn Sripiboon (b), Mongkol Damrongsri (b), Junko Munakata-Marr (c) Abstract: A sequencing batch reactor (SBR) was inoculated with mixed nitrifying bacteria from an anoxic tank at the conventional activated sludge wastewater treatment plant in Nongkhaem, Bangkok, Thailand. This enriched nitrifying culture was maintained under anaerobic conditions using ammonium (NH.sub.4.sup.+) as an electron donor and nitrite (NO.sub.2.sup.-) as an electron acceptor. Autotrophic ammonium oxidizing bacteria survived under these conditions. The enrichment period for anammox culture was over 100 days. Both ammonium and nitrite conversion rates were proportional to the biomass of ammonium oxidizing bacteria; rates were 0.08gN/gVSS/d and 0.05gN/gVSS/d for ammonium and nitrite, respectively, in a culture maintained for 3 months at 42mgN/L ammonium. The nitrogen transformation rate at a ratio of NH.sub.4.sup.+-N to NO.sub.2.sup.--N of 1:1.38 was faster, and effluent nitrogen levels were lower, than at ratios of 1:0.671, 1:2.18, and 1:3.05. Fluorescent in situ hybridization (FISH) was used to identify specific autotrophic ammonium oxidizing bacteria (Nitrosomonas spp., Candidatus Brocadia anammoxidans, and Candidatus Kuenenia stuttgartiensis). The ammonium oxidizing culture maintained at 42mgN/L ammonium was enriched for Nitrosomonas spp. (30%) over Candidati B. anammoxidans and K. stuttgartiensis (2.1%) while the culture maintained at 210mgN/L ammonium was dominated by Candidati B. anammoxidans and K. stuttgartiensis (85.6%). The specific nitrogen removal rate of anammox bacteria (0.6gN/g anammoxVSS/d) was significantly higher than that of ammonium oxidizing bacteria (0.4gN/g Nitrosomonas VSS/d). Anammox bacteria removed up to 979mgN/L/d of total nitrogen (ammonium:nitrite concentrations, 397:582mgN/L). These results suggest significant promise of this approach for application to wastewater with high nitrogen but low carbon content, such as that found in Bangkok. Author Affiliation: (a) Department of Environmental Science, Faculty of Science, Silpakorn University, Nakhon-pathom Province 73000, Thailand (b) Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand (c) Environmental Science and Engineering Division, Colorado School of Mines, Golden, CO 80401, USA Article History: Received 19 June 2007; Revised 16 November 2007; Accepted 8 March 2008