Jin Xin, Liu Mengwen, Zong Yukai, Hu Shiyi, Li Yao, Xu Lu, Bai Xue, Shi Xuan, Jin Pengkang, Song Jina, Wang Xiaochang C
School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi Province 710049, China.
School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi Province 710055, China.
Water Res. 2023 Apr 1;232:119692. doi: 10.1016/j.watres.2023.119692. Epub 2023 Feb 3.
Pre-ozonation coagulation process had a very low and narrow range of ozone dosages for enhancing the dissolved organic matter (DOC) removal efficiency, in which over-oxidation may occur if the ozone dosage was not strictly controlled. In contrast, the proposed hybrid ozonation-coagulation (HOC) process with higher oxidation ability notably inhibited over-oxidation in this study, and exhibited improved DOC removal efficiency compared with coagulation at a much wider range of ozone dosages at different initial pH for the treatment of WWTP effluent. The HOC process also had a higher DOC removal efficiency than pre-ozonation coagulation. According to zeta potential analysis, a rising trend indicated that complexation between organic matter and metal coagulants persisted throughout the HOC process. However, the zeta potential remained almost unchanged during subsequent coagulation after pre-ozonation at high ozone dosages. Synchronous fluorescence spectroscopy analysis revealed that immediate entrapment and complexation between hydrolysed coagulants and oxidized intermediate organic matter occurred in the HOC process. Furthermore, FT-IR analysis showed that more oxygen-containing functional groups were generated, which were effectively trapped by metal coagulants and readily flocculated. To further prove the immediate entrapment and complexation during the HOC process, UPLC-Q-TOF-MS was applied to analyze the intermediate organic matter in the supernatant and flocs. The results implied that C21- organic matter was oxidized and decomposed into C11-C20, and C11-C20 intermediate organic matter was trapped and complexed by metal coagulants once formed, which led to the increase of C11-C20 in the flocs. Nevertheless, the catalytic ozonation process (γ-AlO/O) with the same oxidation ability as the HOC process decomposed the organic matter into C1-C10. XPS analysis further confirmed the immediate entrapment and removal of aliphatic/aromatic carbon and oxygen-containing functional groups during the HOC process. Therefore, over-oxidation can be effectively inhibited, and wide range of ozone dosages was obtained during the HOC process, which facilitate the application of the HOC process.
预臭氧化混凝工艺在提高溶解性有机物（DOC）去除效率方面，臭氧投加量范围很低且狭窄，若臭氧投加量未严格控制，可能会发生过度氧化。相比之下，本研究中所提出的具有更高氧化能力的混合臭氧化 - 混凝（HOC）工艺显著抑制了过度氧化，并且在处理污水处理厂出水时，与混凝相比，在更宽的臭氧投加量范围以及不同初始pH值条件下，表现出更高的DOC去除效率。HOC工艺的DOC去除效率也高于预臭氧化混凝工艺。根据zeta电位分析，上升趋势表明在整个HOC工艺过程中有机物与金属混凝剂之间的络合作用持续存在。然而，在高臭氧投加量的预臭氧化之后的后续混凝过程中，zeta电位几乎保持不变。同步荧光光谱分析表明，在HOC工艺过程中水解混凝剂与氧化后的中间有机物之间立即发生了截留和络合。此外，傅里叶变换红外光谱（FT - IR）分析表明生成了更多的含氧官能团，这些官能团被金属混凝剂有效截留并易于絮凝。为了进一步证明HOC工艺过程中的立即截留和络合，采用超高效液相色谱 - 四极杆飞行时间质谱（UPLC - Q - TOF - MS）分析上清液和絮体中的中间有机物。结果表明，C21 - 有机物被氧化分解为C11 - C20，并且C11 - C20中间有机物一旦形成就被金属混凝剂截留并络合，这导致絮体中C11 - C20含量增加。然而，具有与HOC工艺相同氧化能力的催化臭氧化工艺（γ - AlO/O）将有机物分解为C1 - C10。X射线光电子能谱（XPS）分析进一步证实了在HOC工艺过程中脂肪族/芳香族碳和含氧官能团被立即截留和去除。因此，HOC工艺过程中可以有效抑制过度氧化，并获得较宽的臭氧投加量范围，这有利于HOC工艺的应用。
