The efforts for implementing the anammox process at mainstream conditions with high nitrogen removal rates have gained much attention in the race for achieving an energy-positive urban wastewater treatment plant. Here, the successful and stable long-term operation of an Upflow Anammox Sludge Bed (UAnSB) reactor treating a low-strength synthetic influent amended with ammonium and nitrite for 420 days, and a nitrite-amended pre-treated real urban wastewater for 110 days at temperatures as low as 11 °C is presented. The short and long-term effects of temperature on anammox activity were assessed when the synthetic influent was treated, and the UAnSB reactor was demonstrated to be a robust reactor to confront low temperatures, typically found at mainstream conditions. In fact, a nitrogen loading rate as high as 1.8 ± 0.1 g N L⁻¹ d⁻¹ with 82 ± 4% of nitrogen removal was achieved at 11 °C treating the low-strength synthetic influent. Furthermore, the effect of treating a nitrite-amended pre-treated real urban wastewater at 11 °C at long-term in the UAnSB reactor was evaluated, and a stable operation was achieved with a high average nitrogen removal rate (1.2 ± 0.5 g N L⁻¹ d⁻¹). The relative abundance of anammox bacteria was maintained higher than 70% according to fluorescence in situ hybridization during the whole operation, being Candidatus Brocadia anammoxidans the predominant microbial species. The presence of heterotrophs in the sludge bed was surmised through heterotrophic batch tests, but anammox activity was demonstrated to be higher than heterotrophic activity, even when the synthetic influent was replaced by the nitrite-amended pre-treated real wastewater. The feasibility of operating an enriched anammox reactor at high nitrogen removal rate at long-term at mainstream conditions was demonstrated in this study.

中文翻译：

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主流条件下上流式厌氧污泥床反应器可长期稳定运行

在实现高能效城市污水处理厂的竞赛中，在主流条件下以高氮去除率实施厌氧氨氧化工艺的努力引起了很多关注。在这里，上流厌氧氨氧化污泥床（UAnSB）反应器成功稳定地长期运行，该反应器处理了经铵和亚硝酸盐改性的低强度合成进水420天，以及经过亚硝酸盐改性的实际城市污水处理了110天温度低至11°C。当处理合成进水时，评估了温度对厌氧氨氧化活性的短期和长期影响，并且证明了UAANSB反应器是应对低温的强大反应器，通常在主流条件下都可找到。实际上，氮的加载速率高达1.8±0.1 g NL在11°C下处理低强度合成进水时，去除了82±4％的^-1 d ^-1。此外，评估了在UAnSB反应器中长期处理11°C的亚硝酸盐预处理的实际城市废水的效果，并以较高的平均氮去除率（1.2±0.5 g NL）实现了稳定的运行。^-1 d ^-1）。整个操作过程中，根据荧光原位杂交技术，厌氧菌的相对丰度保持在70％以上。主要的微生物物种。通过异养分批测试可以推测污泥床中是否存在异养菌，但是即使合成进水被亚硝酸盐改良的预处理真实废水代替，厌氧氨氧化活性也被证明高于异养生物活性。这项研究证明了在主流条件下长期以高脱氮率运行富集厌氧氨氧化反应器的可行性。