Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China; Hohai University, College of Environmental Science, Nanjing 210098, China.
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China; Hohai University, College of Environmental Science, Nanjing 210098, China.
Water Res. 2018 Oct 15;143:250-259. doi: 10.1016/j.watres.2018.06.044. Epub 2018 Jun 19.
The residual dissolved organic matter (DOM) and nitrate in sewage treatment plant (STP) effluent have potential negative impacts on the aqueous environment. To that end, we used formic acid (FA) to enhance the photochemical behavior of the photocatalytic membrane for the simultaneous removal of DOM and nitrate from secondary STP effluent. Effluent samples were collected from two different biological treatment processes, Anaerobic-Oxic and Anaerobic-Anoxic-Oxic-membrane bioreactor, respectively. Through Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) analysis, we found that the addition of FA resulted in a similar molecular transformation in different STP effluent samples. Besides, the radical signal of the carboxyl anion could be observed during the photocatalytic process. Based on the results, we proposed the mechanism of the process that carboxyl anion radicals generated by FA could attack DOM and result in further oxidation of the DOM transition state to CO or small molecule by nitrate. Meanwhile, CHON and CHOS compounds in DOM were attacked by the carboxyl anion radicals more easily than CHO compounds. Moreover, long-term use of the membrane confirmed its durability and reusability in practical applications. At a moderate FA concentration and lower hydraulic retention time, the nitrate and DOM removal efficiencies for the sample from JX STP were 68% and 70%, respectively, whereas those of the CD STP sample were 85% and 60%. The removal of DOM and nitrate from different STP effluents using photocatalytic membranes is an advanced approach for the treatment of secondary effluent, and may be applicable to other membranes or systems.
污水处理厂（STP）出水中残留的溶解性有机物（DOM）和硝酸盐对水生态环境具有潜在的负面影响。为此，我们使用甲酸（FA）来增强光催化膜的光化学行为，以从二级 STP 出水中同时去除 DOM 和硝酸盐。废水样品分别取自两种不同的生物处理工艺，即厌氧-好氧和厌氧-缺氧-好氧-膜生物反应器。通过傅里叶变换离子回旋共振质谱（FT-ICR-MS）分析，我们发现 FA 的添加导致不同 STP 出水中的水样发生了相似的分子转化。此外，在光催化过程中可以观察到羧酸根阴离子的自由基信号。基于这些结果，我们提出了该过程的机理，即 FA 产生的羧酸根阴离子自由基可以攻击 DOM，并通过硝酸盐将 DOM 过渡态进一步氧化为 CO 或小分子。同时，DOM 中的 CHON 和 CHOS 化合物比 CHO 化合物更容易受到羧酸根阴离子自由基的攻击。此外，长期使用该膜证实了其在实际应用中的耐用性和可重复使用性。在适中的 FA 浓度和较低的水力停留时间下，JX STP 水样的硝酸盐和 DOM 去除效率分别为 68%和 70%，而 CD STP 水样的去除效率分别为 85%和 60%。利用光催化膜从不同 STP 出水中去除 DOM 和硝酸盐是一种先进的二级出水处理方法，可能适用于其他膜或系统。
