Microcystin-LR Removal by Ozone (O₃) and Vacuum-UV (VUV): The Effect of Chloride Ions

ABSTRACT

Removal of microcystin-LR (MC-LR) by ozone (O₃), vacuum-UV (VUV), and their combination was investigated in the presence of chloride as one of the main solutes present in water. In general, the combined VUV/O₃ process provided the greatest MC-LR removal, with the presence of chloride enhancing the removal efficacy. Formation of chlorine radical species was the primary reason for the observed improvement. The order of MC-LR removal by different processes using UV fluence of around 300 mJ cm⁻², ozone dose of 0.1 mg L⁻¹, and chloride concentration of 120 mg L⁻¹ was as follows: VUV/O₃/Chloride > VUV/O₃ > VUV/Chloride > VUV > O₃. Comparing MC-LR removal by O₃, VUV and VUV/O₃ in synthetic lab samples, spiked with Suwannee River NOM and natural water samples of the same organic concentration, showed the significance of background organics in scavenging ozone in the process. For a given ozone dosage, MC-LR removal by O₃ or VUV/O₃ in natural water was lower than that in the synthetic water samples. The standalone VUV was not affected and the MC-LR removals were identical in both synthetic and natural waters.

KEYWORDS:

• Advanced oxidation
• chloride enhancement
• microcystin-LR degradation
• Ozone
• Suwannee River NOM
• vacuum ultraviolet

Acknowledgments

This study was funded by Qatar National Research Fund (QNRF) while the experiments were conducted in the laboratories of the Chemical and Biological Engineering Department at the University of British Columbia. Many thanks to Mr. Kevin Brown from Metro Vancouver for providing water samples from Capilano Watershed.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the Qatar National Research Fund.