Combined Nitritation鈥揂nammox: Advances in Understanding Process Stability

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• 作者：Adriano Joss ; Nicolas Derlon ; Clementine Cyprien ; Sabine Burger ; Ilona Szivak ; Jacqueline Traber ; Hansruedi Siegrist ; Eberhard Morgenroth
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：November 15, 2011
• 年：2011
• 卷：45
• 期：22
• 页码：9735-9742
• 全文大小：928K
• 年卷期：v.45,no.22(November 15, 2011)
• ISSN：1520-5851

文摘

Efficient nitrogen removal from wastewater containing high concentrations of ammonium but little organic substrate has recently been demonstrated by several full-scale applications of the combined nitritation鈥揳nammox process. While the process efficiency is in most cases very good, process instabilities have been observed to result in temporary process failures. In the current study, conditions resulting in instability and strategies to regain efficient operation were evaluated. First, data from full-scale operation is presented, showing a sudden partial loss of activity followed by recovery within less than 1 month. Results from laboratory-scale experiments indicate that these dynamics observed in full scale can be caused by partial inhibition of the ammonia oxidizing bacteria (AOB), while anammox inhibition is a secondary effect due to temporarily reduced O₂ depletion. Complete anammox inhibition is observed at 0.2 mg O₂路L^鈥?, resulting in NO₂^{鈥?/sup> accumulation. However, this inhibition of anammox is reversible within minutes after O₂ depletion. Thus, variable AOB activity was identified as the key to reactor stability. With appropriate interpretation of the online NH₄+ signal, accumulation of NO₂鈥?/sup> can be detected indirectly and used to signal an imbalance of O₂ supply and AOB activity (no suitable online NO₂鈥?/sup> electrode is currently available). Second, increased abundance of nitrite-oxidizing bacteria (NOB; competing with anammox for NO₂鈥?/sup>) is known as another cause of instability. Based on a comparison of parallel full-scale reactors, it is suggested that an infrequent and short-term increased O₂ supply (e.g., for maintenance of aerators) that exceeds prompt depletion of oxygen by AOB may have caused increased NOB abundance. The volumetric air supply as a proxy for O₂ supply thus needs to be linked to AOB activity. Further, NOB can be washed out of the system during regular operation if the system is operated at a sludge age in the range of 45 days and by controlling the air supply according to the NO₃鈥?/sup> concentration in the treated effluent. Early detection of growing NOB abundance while the population is still low can help guide process operation and it is suggested that molecular methods of quantifying NOB abundance should be tested.}