School of Environmental Science and Engineering, Qingdao University, Qingdao 266071, PR China.
Qingdao Water Group Co. Ltd., Qingdao 266100, China.
Sci Total Environ. 2023 Jul 1;880:163320. doi: 10.1016/j.scitotenv.2023.163320. Epub 2023 Apr 5.
The Anaerobic-oxic-anoxic (AOA) process is a carbon-saving and high-efficiency way to treat municipal wastewater and gets more attention. Recent reports suggest that in the AOA process, well-performed endogenous denitrification (ED), conducted by glycogen accumulating organisms (GAOs), is crucial to advanced nutrient removal. However, the consensuses about starting up and optimizing AOA, and in-situ enriching GAOs, are still lacking. Hence, this study tried to verify whether AOA could be established in an ongoing anaerobic-oxic (AO) system. For this aim, a lab-scale plug-flow reactor (working volume of 40 L) previously operated under AO mode for 150 days, during that 97.87 % of ammonium was oxidized to nitrate and 44.4 % of orthophosphate was absorbed. Contrary to expectations, under AOA mode, little nitrate reduction (only 6.3 mg/L within 5.33 h) indicated the failure of ED. According to high-throughput sequencing analysis, GAOs (Candidatus_Competibacter and Defluviicoccus) were enriched within the AO period (14.27 % and 3 %) and then still dominated during the AOA period (13.9 % and 10.07 %) but contributed little to ED. Although apparent alternate orthophosphate variations existed in this reactor, no typical phosphorus accumulating organisms were abundant (< 2 %). More than that, within the long-term AOA operation (109 days), the nitrification weakened (merely 40.11 % of ammonium been oxidized) since the dual effects of low dissolved oxygen and long unaerated duration. This work reveals the necessity of developing practical strategies for starting and optimizing AOA, and then three aspects in future studying are pointed out.
厌氧-好氧-缺氧（AOA）工艺是一种节约碳且高效的处理城市污水的方法，受到了更多关注。最近的报道表明，在 AOA 工艺中，通过糖原积累菌（GAOs）进行的高效内源反硝化（ED）对于高级养分去除至关重要。然而，关于启动和优化 AOA 以及原位富集 GAOs 的共识仍然缺乏。因此，本研究试图验证 AOA 是否可以在正在运行的厌氧-好氧（AO）系统中建立。为此，使用一个实验室规模的推流式反应器（工作体积为 40 L），该反应器之前以 AO 模式运行了 150 天，在此期间，97.87%的氨氮被氧化为硝酸盐，44.4%的正磷酸盐被吸收。与预期相反，在 AOA 模式下，硝酸盐还原很少（5.33 小时内仅 6.3 mg/L），表明 ED 失败。根据高通量测序分析，GAOs（Candidatus_Competibacter 和 Defluviicoccus）在 AO 期间得到了富集（14.27%和 3%），然后在 AOA 期间仍然占主导地位（13.9%和 10.07%），但对 ED 的贡献很小。尽管该反应器中存在明显的交替正磷酸盐变化，但没有丰富的典型磷积累菌（<2%）。更重要的是，在长期的 AOA 运行（109 天）中，硝化作用减弱（仅有 40.11%的氨氮被氧化），这是由于低溶解氧和长时间缺氧的双重影响。这项工作揭示了开发启动和优化 AOA 的实用策略的必要性，并指出了未来研究的三个方面。
