Disinfection by-product formation during UV/Chlorine treatment of pesticides in a novel UV-LED reactor at 285 nm and the mitigation impact of GAC treatment 机翻标题: 暂无翻译,请尝试点击翻译按钮。

2020-02-03

The UVChlorine process has gained attention in recent years due to the high quantum yield and absorbance of the chlorine species. However, there are still many unknowns around its application as a treatment for drinking water. The potential for the formation of disinfection byproducts (DBPs) is one of them. There are no studies reporting on the formation of trihalomethanes (THMs) or haloacetic acids (HAAs) in complex matrices, such as real source waters, at UV wavelengths tailored to the UVChlorine process, which has been possible thanks to the development of light emitting diodes (LEDs). In addition, consideration of mitigation measures that might be needed after UVChlorine treatment for full scale application have not been previously reported. Specifically, the novelty of this work resides in the use of an innovative reactor using UVLEDs emitting at 285 nm for the removal of three pesticides (metaldehyde, carbetamide and mecoprop), the evaluation of THM, HAA and bromate formation in real water sources by UVChlorine treatment and the mitigation effect of subsequent GAC treatment. A new parameter, the applied optical dose (AOD), has been defined for UV reactors, such as the one in the present study, where the irradiated volume is nonuniform. The results showed the feasibility of using the UVChlorine process with LEDs, although a compromise is needed between pH and chlorine concentration to remove pesticides while minimising DBP formation. Overall, the UVChlorine process did not significantly increase THM or HAA formation at pH 7.98.2 at the studied wavelength. At acidic pH, however, THM formation potential increased up to 30% after UVChlorine treatment with concentrations up to 60 gL. HAA formation potential increased between 100 and 180%, although concentrations never exceeded 35 gL. In all cases, GAC treatment mitigated DBP formation, reducing THM formation potential to concentrations between 3 and 16 gL, and HAA formation potential between 4 and 30 gL.

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