Zhu Tingting, Ding Jiazeng, Liu Yingrui, Li Xufeng, Wang Zhiwen, Liu Yiwen
School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, PR China.
School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, PR China.
Sci Total Environ. 2023 Dec 10;903:166126. doi: 10.1016/j.scitotenv.2023.166126. Epub 2023 Aug 8.
Sulfur-driven autotrophic denitrification (SAD) is considered as an effective alternative to traditional heterotrophic denitrification (HD) due to its cheap, low sludge production and non-toxicity. Nitrous oxide (NO) as an intermediate product inevitably was generated at the limited supply of electron donor or unbalanced electron distribution condition during the denitrification process. Recently, autotrophic denitrification biofilters were conclusively implemented for advanced nitrogen removal in wastewater treatment plant (WWTP). However, residual organic sources after wastewater treatment could affect the electron distribution among denitrifying reductases and few studies are known about this issue. In this study, several lab-scale biofilters packed with elemental sulfur slices were applied to explore the electron distribution characteristics of autotrophic denitrification through the combination of different nitrogen oxides (NO). The results clearly delineated that the different combination of nitrogen oxides had a remarkable effect on the electron distribution. In any case, the electrons likely flow toward nitrate reductase (Nar) under a single nitrogen oxide combination, followed by nitrite reductase (Nir) and nitrous oxide reductase (Nos). The concurrent presence of multiple electron acceptors resulted in most electrons flowing toward Nar, and least toward Nos. Compared to traditional SAD, the reduction rate of nitrogen oxide in the sulfur-driven autotrophic denitrification with influent of organic source (OSAD) was greatly improved. The maximum value of the true specific rates of NO in OSAD process was 9.43 mg-N/g-VSS/h. It was increased by 8.26 folds higher than that in traditional SAD. The electrons were more easily distributed to Nos with the addition of sodium acetate, which further promoted the NO reduction. This study will provide theoretical support for controlling NO release in SAD biofilters.
硫驱动自养反硝化（SAD）因其成本低廉、污泥产量低且无毒，被认为是传统异养反硝化（HD）的有效替代方法。在反硝化过程中，当电子供体供应有限或电子分布不平衡时，不可避免地会产生中间产物氧化亚氮（N₂O）。最近，自养反硝化生物滤池已被最终应用于污水处理厂（WWTP）的深度脱氮。然而，废水处理后的残留有机源可能会影响反硝化还原酶之间的电子分布，而关于这个问题的研究很少。在本研究中，应用了几个填充元素硫片的实验室规模生物滤池，通过不同氮氧化物（NOₓ）的组合来探索自养反硝化的电子分布特征。结果清楚地表明，不同的氮氧化物组合对电子分布有显著影响。在任何情况下，在单一氮氧化物组合下，电子可能流向硝酸还原酶（Nar），其次是亚硝酸还原酶（Nir）和氧化亚氮还原酶（Nos）。多种电子受体同时存在导致大多数电子流向Nar，而流向Nos的最少。与传统SAD相比，有机源进水的硫驱动自养反硝化（OSAD）中氮氧化物的还原速率有了很大提高。OSAD过程中NO的真实比速率最大值为9.43 mg-N/g-VSS/h。比传统SAD提高了8.26倍。添加乙酸钠后，电子更容易分布到Nos，进一步促进了NO的还原。本研究将为控制SAD生物滤池中N₂O的释放提供理论支持。
