College of Environmental Science and Engineering and Key Laboratory of Environmental Biology and Pollution Control (Ministry of Education), Hunan University, Changsha, 410082, PR China.
College of Environmental Science and Engineering and Key Laboratory of Environmental Biology and Pollution Control (Ministry of Education), Hunan University, Changsha, 410082, PR China.
J Environ Manage. 2022 Nov 15;322:116098. doi: 10.1016/j.jenvman.2022.116098. Epub 2022 Sep 5.
Diclofenac (DCF), a nonsteroidal anti-inflammatory drug, is one of the most commonly detected pharmaceuticals in wastewater treatment plants. However, the fate of DCF in waste activated sludge (WAS) anaerobic fermentation has not been well-understood so far. This work therefore aims to comprehensively reveal whether and how DCF is transformed in WAS mesophilic anaerobic fermentation through both experimental investigation and density functional theory (DFT) calculation. Experimental results showed that ∼28.8% and 45.8% of DCF were respectively degraded during the batch and long-term fermentation processes. Based on the detected intermediates and DFT-predicted active sites, three metabolic pathways, i.e., chlorination, hydroxylation, and dichlorination, responsible for DCF transformation were proposed. DFT calculation also showed that the Gibbs free energy (ΔG) of the three transformation pathways was respectively 19.0, -4.3, and -19.3 kcal/mol, suggesting that the latter two reactions (i.e., hydroxylation and dichlorination) were thermodynamically favorable. Illumina MiSeq sequencing analyses revealed that DCF improved the populations of complex organic degradation microbes such as Proteiniclasticum and Tissierellales, which was in accord with the chemical analyses above. This work updates the fundamental understanding of the degradation of DCF in WAS anaerobic fermentation process and enlightens engineers to apply theoretical calculation to the field of sludge treatment or other complex microbial ecosystems.
双氯芬酸（DCF）是一种非甾体抗炎药，是污水处理厂中最常检测到的药物之一。然而，迄今为止，DCF 在废活性污泥（WAS）厌氧发酵中的命运还没有被很好地理解。因此，这项工作旨在通过实验研究和密度泛函理论（DFT）计算全面揭示 DCF 在 WAS 中温厌氧发酵中是否以及如何转化。实验结果表明，在批式和长期发酵过程中，约有 28.8%和 45.8%的 DCF 分别被降解。基于检测到的中间体和 DFT 预测的活性位点，提出了三种代谢途径，即氯化、羟化和二氯化，负责 DCF 的转化。DFT 计算还表明，三种转化途径的吉布斯自由能（ΔG）分别为 19.0、-4.3 和-19.3 kcal/mol，表明后两个反应（即羟化和二氯化）在热力学上是有利的。Illumina MiSeq 测序分析表明，DCF 提高了复杂有机降解微生物的种群，如蛋白分解菌和 Tissierellales，这与上述化学分析一致。这项工作更新了对 DCF 在 WAS 厌氧发酵过程中降解的基本认识，并启发工程师将理论计算应用于污泥处理或其他复杂微生物生态系统领域。
