Third K A, Sliekers A O, Kuenen J G, Jetten M S
Department of Biotechnology, Murdoch University, Perth, Western Australia.
Syst Appl Microbiol. 2001 Dec;24(4):588-96. doi: 10.1078/0723-2020-00077.
The CANON system (Completely Autotrophic Nitrogen Removal Over Nitrite) can potentially remove ammonium from wastewater in a single, oxygen-limited treatment step. The usefulness of CANON as an industrial process will be determined by the ability of the system to recover from major disturbances in feed composition. The CANON process relies on the stable interaction between only two bacterial populations: Nitrosomonas-like aerobic and Planctomycete-like anaerobic ammonium oxidising bacteria. The effect of extended periods of ammonium limitation was investigated at the laboratory scale in two different reactor types (sequencing batch reactor and chemostat). The lower limit of effective and stable nitrogen removal to dinitrogen gas in the CANON system was 0.1 kg N m(-3) day(-1). At this loading rate, 92% of the total nitrogen was removed. After prolonged exposure (> 1 month) to influxes lower than this critical NH4+-influx, a third population of bacteria developed in the system and affected the CANON reaction stoichiometry, resulting in a temporary decrease in nitrogen removal from 92% to 57%. The third group of bacteria were identified by activity tests and qualititative FISH (Fluorescence In Situ Hybridisation) analysis to be nitrite-oxidising Nitrobacter and Nitrospira species. The changes caused by the NH4+-limitation were completely reversible, and the system re-established itself as soon as the ammonium limitation was removed. This study showed that CANON is a robust system for ammonium removal, enduring periods of up to one month of ammonium limitation without irreversible damage.
CANON系统（亚硝酸盐型完全自养脱氮）能够在单一的、氧气受限的处理步骤中从废水中去除铵。CANON作为一种工业工艺的实用性将取决于该系统从进料组成的重大干扰中恢复的能力。CANON工艺仅依赖于两种细菌群体之间的稳定相互作用：类硝化单胞菌好氧菌和类浮霉菌厌氧菌。在实验室规模下，在两种不同的反应器类型（序批式反应器和恒化器）中研究了长期铵限制的影响。CANON系统中有效且稳定地将氮去除为氮气的下限为0.1 kg N m(-3) 天(-1)。在此负荷率下，92%的总氮被去除。在长时间（>1个月）暴露于低于此临界NH4+流入量的情况下，系统中出现了第三类细菌群体，并影响了CANON反应化学计量，导致氮去除率从92%暂时降至57%。通过活性测试和定性荧光原位杂交（FISH）分析确定第三类细菌为亚硝酸盐氧化菌硝化杆菌属和硝化螺菌属。由NH4+限制引起的变化是完全可逆的，一旦铵限制被解除，系统就会自行恢复。这项研究表明，CANON是一种强大的铵去除系统，能够承受长达一个月的铵限制期而不会受到不可逆转的损害。
