Inactivation of Staphylococcus aureus in water by dielectric barrier discharge plasma jet: The role of inorganic ions, organic matter, and turbidity

Pathogenic microorganisms in water pose a potentially serious threat to human health. As an advanced oxidation technology, plasma sterilization has been widely used to kill pathogens in water. However, few studies on the effects of various substances in natural water bodies, such as common ions (Ca 2+ , Mg 2+ , Cl − , SO 4 2− , Fe 2+ ), as well as natural organic matter (humic acid, HA) and turbidity (diatomite), on plasma sterilization. This study used a dielectric barrier discharge (DBD) plasma jet to inactivate Staphylococcus aureus ( S. aureus ) in pure water and simulated water containing the above substances. We systematically investigated how experimental parameters and water constituents affected S. aureus inactivation. Results showed that Ca 2+ , Mg 2+ , Cl − , natural organic matter (humic acid, HA), and turbidity (diatomite) inhibited inactivation, while Fe 2+ and SO 4 2− promoted it. Additionally, the MDA content, cell metabolic capacity, and cell integrity of S. aureus in pure water and simulated water system were detected before and after plasma treatment. The results showed that RS produced by plasma attacked the cell membrane of S. aureus , causing a rupture. RS also accelerated oxidative stress and disrupted cell metabolism, ultimately leading to cell death. Long-lived reactive species (RS) in water induced by plasma, such as (H 2 O 2 , NO 3 − , NO 2 − ), had no significant effect in plasma inactivation. The positive role of short-lived reactive species ( O 2 − , 1 O 2 and OH) in the inactivation of S. aureus was verified by ESR and quenching experiments, especially •O 2 − .