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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

Sludge from an anoxic tank at the centralized wastewater treatment plant, Nong Khaem, Bangkok, Thailand, was inoculated in an anaerobic sequencing batch reactor (ASBR). The optimal compositions and operating conditions of the stock of autotrophic ammonium oxidizing bacteria medium were determined. The process of oxidizing ammonium with bacteria under anaerobic conditions is often referred to as the Anammox process (NO2- to N2 gas, using NH4+ as the electron donor and NO2- as the electron acceptor). The startup period for the anammox culture took more than three months. With ammonium and nitrite concentration ratios of 1:1.38 and 1:1.6, the nitrogen conversion rate zero order. Fluorescent in situ hybridization (FISH) was used to identify specific autotrophic ammonium oxidizing bacteria (Nitrosomonas spp., Candidatus Brocadia anammoxidans, and Candidatus Kuenenia stuttgartiensis). Results from this work demonstrated a shift in the species of ammonium oxidizing bacteria from Nitrosomonas spp. to Candidati Brocadia anammoxidans and Kuenenia stuttgartiensis, with increased ammonium concentrations from 3 mM to 15 mM. Under NH4+:NO2- ratios of 1:1.38 and 1:1.6 the ammonium oxidizing bacteria were able to remove both ammonium and nitrite simultaneously. The specific nitrogen removal rate of the anammox bacteria (Candidati Brocadia anammoxidans and Kuenenia stuttgartiensis) was significantly higher than that of anaerobic ammonium oxidizing bacteria (Nitrosomonas spp.). Anaerobic ammonium oxidizing bacteria (Candidati Brocadia anammoxidans and Kuenenia stuttgartiensis) are strict anaerobes. [ABSTRACT FROM AUTHOR]