Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, Queensland 4072, Australia.
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China.
Environ Sci Technol. 2022 Aug 16;56(16):11578-11588. doi: 10.1021/acs.est.1c07522. Epub 2022 Jul 25.
Acidic nitrification is attracting wide attention because it can enable robust suppression of nitrite-oxidizing bacteria (NOB) in wastewater treatment. This study reports a comprehensive assessment of the novel acidic nitrification process to identify the key factors that govern stable nitrite accumulation. A laboratory-scale moving-bed biofilm reactor receiving low-alkalinity wastewater was continuously operated under acidic conditions (pH < 6) for around two years, including nine stages varying influent and operational conditions. The results revealed that nitrite accumulation was related to three factors, i.e., influent ammonium concentration, operating pH, and ammonia-oxidizing microbial community. These three factors impact nitrite accumulation by altering the concentration of free nitrous acid (FNA), which is a potent inhibitor of NOB. The critical FNA concentration is approximately one part per million (ppm, ∼1 mg HNO-N/L), above which nitrite accumulation is stably maintained in an acidic nitrifying system. The findings of this study suggest that stable nitrite accumulation via acidic ammonia oxidation can be maintained under a range of influent and operational conditions, as long as a ppm-level of FNA is established. Taking low-strength mainstream wastewater (40-50 mg NH-N/L) with limited alkalinity as an example, stable nitrite accumulation was experimentally demonstrated at a pH of 4.35, under which an FNA of 2.3 ± 0.6 mg HNO-N/L was attained. Under these conditions, Nitrosoglobus became the only ammonia oxidizer detectable by 16S rRNA gene sequencing. The results of this study deepen our understanding of acidic nitrifying systems, informing further development of novel wastewater treatment technologies.
酸化硝化作用因其能有效抑制废水处理中硝化细菌（Nitrite-oxidizing bacteria，NOB）的生长而受到广泛关注。本研究对新型酸化硝化工艺进行了全面评估，以确定控制稳定亚硝酸盐积累的关键因素。在实验室规模的移动床生物膜反应器中，采用低碱度废水在酸性条件（pH < 6）下连续运行约两年，包括 9 个阶段，改变进水和操作条件。结果表明，亚硝酸盐积累与三个因素有关，即进水氨氮浓度、操作 pH 值和氨氧化微生物群落。这三个因素通过改变游离亚硝酸（Free nitrous acid，FNA）的浓度来影响亚硝酸盐的积累，而 FNA 是一种有效的 NOB 抑制剂。临界 FNA 浓度约为百万分之一（ppm，~1mg HNO-N/L），在此浓度以上，酸性硝化系统中可以稳定维持亚硝酸盐的积累。本研究结果表明，只要建立 ppm 级的 FNA，就可以在一系列进水和操作条件下通过酸性氨氧化维持稳定的亚硝酸盐积累。以低强度主流废水（40-50mg NH-N/L）和有限的碱度为例，在 pH 4.35 下进行了稳定亚硝酸盐积累的实验，在此条件下获得了 2.3±0.6mg HNO-N/L 的 FNA。在这些条件下，16S rRNA 基因测序检测到唯一的氨氧化菌为 Nitrosoglobus。本研究加深了我们对酸化硝化系统的理解，为新型废水处理技术的进一步发展提供了依据。
