Hausherr D, Niederdorfer R, Bürgmann H, Lehmann M F, Magyar P, Mohn J, Morgenroth E, Joss A
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf 8600, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, 6047, Switzerland.
Water Res X. 2022 Jun 16;16:100145. doi: 10.1016/j.wroa.2022.100145. eCollection 2022 Aug 1.
For two decades now, partial nitritation anammox (PNA) systems were suggested to more efficiently remove nitrogen (N) from mainstream municipal wastewater. Yet to date, only a few pilot-scale systems and even fewer full-scale implementations of this technology have been described. Process instability continues to restrict the broad application of PNA. Especially problematic are insufficient anammox biomass retention, the growth of undesired aerobic nitrite-oxidizers, and nitrous oxide (NO) emissions. In this study, a two-stage mainstream pilot-scale PNA system, consisting of three reactors (carbon pre-treatment, nitritation, anammox - 8 m each), was operated over a year, treating municipal wastewater. The aim was to test whether both, robust autotrophic N removal and high effluent quality, can be achieved throughout the year. A second aim was to better understand rate limiting processes, potentially affecting the overall performance of PNA systems. In this pilot study, excellent effluent quality, in terms of inorganic nitrogen, was accomplished (average effluent concentrations: 0.4 mgNH-N/L, 0.1 mgNO-N/L, 0.9 mgNO-N/L) even at wastewater temperatures previously considered problematic (as low as 8 °C). N removal was limited by nitritation rates (84 ± 43 mgNH-N/L/d), while surplus anammox activity was observed at all times (178 ± 43 mgN/L/d). Throughout the study, nitrite-oxidation was maintained at a low level (<2.5% of ammonium consumption rate). Unfortunately, high NO emissions from the nitritation stage (1.2% of total nitrogen in the influent) were observed, and, based on natural isotope abundance measurements, could be attributed to heterotrophic denitrification. batch experiments were conducted to identify the role of dissolved oxygen (DO) and organic substrate availability in NO emission-mitigation. The addition of organic substrate, to promote complete denitrification, was not successful in decreasing NO emission, but increasing the DO from 0.3 to 2.9 mgO/L decreased NO emissions by a factor of 3.4.
二十年来，人们一直认为部分亚硝化厌氧氨氧化（PNA）系统能更有效地从城市污水主流中去除氮。然而迄今为止，仅有少数中试规模的系统，而该技术的全规模应用更是少之又少。工艺稳定性仍然限制着PNA的广泛应用。尤其成问题的是厌氧氨氧化生物质保留不足、不希望出现的好氧亚硝酸盐氧化菌的生长以及一氧化二氮（N₂O）排放。在本研究中，一个由三个反应器（碳预处理、亚硝化、厌氧氨氧化，每个反应器8米）组成的两级主流中试规模PNA系统运行了一年，处理城市污水。目的是测试全年能否实现稳健的自养脱氮和高出水水质。第二个目的是更好地理解可能影响PNA系统整体性能的限速过程。在这个中试研究中，即使在先前被认为有问题的废水温度（低至8℃）下，也实现了优异的无机氮出水水质（平均出水浓度：0.4mgNH₃-N/L、0.1mgNO₂-N/L、0.9mgNO₃-N/L）。脱氮受亚硝化速率限制（84±43mgNH₃-N/L/d），而始终观察到有过剩的厌氧氨氧化活性（178±43mgN/L/d）。在整个研究过程中，亚硝酸盐氧化维持在较低水平（<铵消耗速率的2.5%）。不幸的是，观察到亚硝化阶段有较高的N₂O排放（占进水总氮的1.2%），并且根据天然同位素丰度测量，这可能归因于异养反硝化。进行了批次实验以确定溶解氧（DO）和有机底物可用性在减轻N₂O排放中的作用。添加有机底物以促进完全反硝化，未能成功降低N₂O排放，但将DO从0.3mgO₂/L提高到2.9mgO₂/L使N₂O排放减少了3.4倍。
