Disinfection performances of stored acidic and neutral electrolyzed waters generated from brine solution

The feasibility of storing two electrolyzed waters (EW), acidic (AEW) and neutral (NEW), were elucidated through Escherichia coli O157:H7 and Salmonella typhii inactivation experiments. Free chlorine (FC) loss, pH and oxidation-reduction potentials were monitored for 30 days. Initial activities of fresh EWs were determined at 5 mg Cl(2)·min/L for 8 Log(10) inactivations of both strains. However, stored EWs exhibited activity declines which were associated to FC losses. All FC loss rates were first-order; AEWs underwent two phases of decays while NEWs had single decay rate constants. Two FC loss mechanisms were identified: chlorine (Cl(2)) volatilization and hypochlorous acid (HOCl) decomposition, wherein Cl(2) volatilization occurred at a faster rate. Chlorine volatilization was primarily influenced by storage condition as indicated by intensive FC losses on EWs stored in open vessels. Under the same storage conditions (open or closed), Cl(2)-rich AEW experienced higher FC losses which indicated the higher stability of HOCl-rich NEW. Overall, FC losses could be minimized if (1) samples are stored in closed vessels and (2) Cl(2) is not the main chlorine component. NEW in closed vessel is the most feasible system for EW storage; its initial activity (8 Log(10) inactivation) was preserved for up to 17 days.