ENFOCHEM, IDAEA-CSIC, c/Jordi Girona 18-26, 08034 Barcelona, Spain; Catalan Institute for Water Research (ICRA), Emili Grahit 101, 17003 Girona, Spain; Department of Chemistry, University of Girona, c/ Maria Aurèlia Capmany, 69, E-17003 Girona, Spain.
ENFOCHEM, IDAEA-CSIC, c/Jordi Girona 18-26, 08034 Barcelona, Spain.
Sci Total Environ. 2022 Feb 10;807(Pt 1):150533. doi: 10.1016/j.scitotenv.2021.150533. Epub 2021 Sep 28.
Diclofenac (DCF) is a highly consumed non-steroidal anti-inflammatory drug that is excreted partially metabolized and is poorly removed during wastewater treatment. Previous findings demonstrated that DCF in wastewater treatment plants (WWTP) is partially removed to nitro/nitroso compounds. The reactive nitrogen species, that are microbially produced during nitrification in the activated sludge of WWTP, were suspected to be involved in the transformation of DCF. Therefore, here, we investigated the molecular features governing such biotransformation and the role played by nitrifying bacteria by biodegradation experiments at lab scale in enriched nitrifying sludge bioreactors spiked with DCF and other structurally related non-steroidal anti-inflammatory drugs (NSAIDs). We provided evidence of the incorporation of NO/NO groups into DCF originated from ammonia by isotopically labelled biodegradation experiments. Nitroso and nitro-derivatives were tentatively identified for all NSAIDs studied and biotransformation mechanisms were proposed. Our findings from biodegradation experiments performed under different incubation conditions suggested that biotransformation of DCF and its related NSAIDs might not only be microbially mediated by ammonia oxidizing bacteria, but other nitrifiers co-occurring in the activated sludge as ammonia oxidizing archaea and nitrite oxidizing bacteria. Follow-up studies should be conducted to disentangle such complex behaviour in order to improve removal of these contaminants in WWTPs.
双氯芬酸（DCF）是一种高消耗的非甾体抗炎药，部分代谢后排出，且在废水处理过程中去除效果不佳。先前的研究结果表明，废水中的 DCF 在污水处理厂（WWTP）中部分转化为硝基/亚硝基化合物。人们怀疑 WWTP 中活性污泥硝化过程中产生的反应性氮物种参与了 DCF 的转化。因此，在这里，我们通过在添加 DCF 和其他结构相关的非甾体抗炎药（NSAIDs）的富硝化污泥生物反应器中进行实验室规模的生物降解实验，研究了控制这种生物转化的分子特征以及硝化细菌的作用。我们通过同位素标记的生物降解实验提供了证据，证明氨将 NO/NO 基团掺入源自 DCF 的物质中。我们暂定鉴定了所有研究的 NSAIDs 的亚硝基和硝基衍生物，并提出了生物转化机制。根据不同的孵育条件进行的生物降解实验的结果表明，DCF 和其相关 NSAIDs 的生物转化可能不仅由氨氧化细菌介导，而且还可能由氨氧化古菌和亚硝酸盐氧化菌等在活性污泥中共同存在的其他硝化剂介导。为了提高 WWTP 中这些污染物的去除效率，应该进行后续研究以阐明这种复杂的行为。
