Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, Ministry of Ecology and Environment, Wuhan 430074, Hubei, China.
Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, Ministry of Ecology and Environment, Wuhan 430074, Hubei, China.
Environ Int. 2022 Sep;167:107389. doi: 10.1016/j.envint.2022.107389. Epub 2022 Jul 2.
Chlorination disinfection has been widely used to kill the pathogenic microorganisms in wastewater sludge during the special Covid-19 period, but sludge chlorination might cause the generation of harmful disinfection byproducts (DBPs). In this work, the transformation of extracellular polymeric substance (EPS) and mechanisms of Cl-DBPs generation during sludge disinfection by sodium hypochlorite (NaClO) were investigated using multispectral analysis in combination with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The microorganism Escherichia coli (E. coli) was effectively inactivated by active chlorine generated from NaClO. However, a high diversity of Cl-DBPs were produced with the addition of NaClO into sludge, causing the increase of acute toxicity on Q67 luminous bacteria of chlorinated EPS. A variety of N-containing molecular formulas were produced after chlorination, but N-containing DBPs were not detected, which might be the indicative of the dissociation of -NH groups after Cl-DBPs generated. Additionally, the release of N-containing compounds was increased in alkaline environment caused by NaClO addition, resulted in more Cl-DBPs generation via nucleophilic substitutions. Whereas, less N-compounds and Cl-DBPs were detected after EPS chlorination under acidic environment, leading to lower cell cytotoxicity. Therefore, N-containing compounds of lignin derivatives in sludge were the major Cl-DBPs precursors, and acidic environment could control the release of N-compounds by eliminating the dissociation of functional groups in lignin derivatives, consequently reducing the generation and cytotoxicity of Cl-DBPs. This study highlights the importance to control the alkalinity of sludge to reduce Cl-DBPs generation prior to chlorination disinfection process, and ensure the safety of subsequential disposal for wastewater sludge.
在新冠疫情特殊时期，氯化消毒被广泛应用于杀死污水污泥中的致病微生物，但污泥氯化可能会导致有害消毒副产物（DBPs）的生成。在这项工作中，使用多光谱分析结合傅里叶变换离子回旋共振质谱（FTICR-MS）研究了次氯酸钠（NaClO）消毒过程中胞外聚合物（EPS）的转化和 Cl-DBPs 生成的机制。活性氯（由 NaClO 产生）有效地使大肠杆菌（E. coli）失活。然而，当向污泥中添加 NaClO 时，会产生多种 Cl-DBPs，导致氯化 EPS 对 Q67 发光菌的急性毒性增加。氯化后产生了多种含氮分子公式，但未检测到含氮 DBPs，这可能表明 Cl-DBPs 生成后 -NH 基团的解离。此外，由于 NaClO 的添加会导致碱性环境中释放出更多的含氮化合物，从而通过亲核取代反应生成更多的 Cl-DBPs。而在酸性环境下进行 EPS 氯化时，检测到的含氮化合物和 Cl-DBPs 较少，导致细胞毒性较低。因此，污泥中木质素衍生物的含氮化合物是 Cl-DBPs 的主要前体，酸性环境可以通过消除木质素衍生物中官能团的解离来控制含氮化合物的释放，从而减少 Cl-DBPs 的生成和细胞毒性。本研究强调了在氯化消毒前控制污泥碱度以减少 Cl-DBPs 生成的重要性，并确保后续污水污泥处置的安全性。
