Impact of metal ions on PMS/Cl− disinfection efficacy: Enhancing or impeding microbial inactivation?

Abstract

Peroxymonosulfate (PMS) is an eco-friendly disinfectant gaining attention. This study examined the influence of metal ions (Co(II), Cu(II), Fe(II)) on PMS disinfection with chloride ions (Cl−) against waterborne microorganisms, encompassing both bacteria and fungal spores. The findings elucidated that metal ions augment the inactivation of bacteria in the PMS/Cl− system while concurrently impeding the inactivation of fungal spores. Specifically, the PMS/Co(II)/Cl− process increased E. coli inactivation rates by 2.25 and 2.75 times compared to PMS/Co(II) and PMS/Cl−, respectively. Conversely, PMS/Me(II)/Cl− generally exhibited a diminished inactivation capacity against the three fungal spores compared to PMS/Cl−, albeit surpassing the efficacy of PMS/Me(II). For instance, the inactivation levels of A. niger by PMS/Cl−, PMS/Cu(II)/Cl−, and PMS/Cu(II) are 4.47-log, 1.92-log, and 0.11-log, respectively. Notably, fungal spores demonstrated a substantially higher resistance to disinfectants compared to bacteria. Differences in microbial susceptibility were linked to cell wall structure, composition, antioxidant defenses, and reactive species generation, such as hydroxyl radicals (•OH), sulfate radicals (SO4•−), and reactive chlorine species (RCS). This study demonstrated the novel and unique phenomenon of metal ions' dual role in modulating the PMS/Cl− disinfection process, which has not been reported before and has important implications for the field of water treatment.