Bacillus spores are resistant to disinfection methods and they represent a potential threat that requires improved methods to ensure water safety. Bacillus thuringiensis (BT) and B. anthracis Sterne (BA) spores were used to investigate the effectiveness of the electrochemical (EC) disinfection process. We tested the quaternary metal oxide (TiO2–Sb2O5–SnO2–RuO2) as the anode material in an EC cell for the inactivation of the spores. The presence of chloride ions at low concentrations was found to be critical for the effective inactivation of BT spores. Active chlorine was produced in-situ by anodic oxidation of chloride in the solutions. Local tap water used as a realistic test solution was found to contain average chloride concentrations of 1.2 mM. High concentrations of active chlorine were generated in the range of 0.35 to 0.5 mM (25 to 35 mg/L) to ensure that the high concentrations of spores were inactivated. We showed that the amount of active chlorine produced in the EC cell can be readily controlled by the operating conditions, including potential, flow rate and chloride content. Scanning electron images of the EC treated spores indicate damage to the outer membranes resulting in disruption and leakage of the spore contents. EC water disinfection processes using inexpensive electrode materials are a promising alternative as shown by inactivation of challenging biological threats such as Bacillus spores.
Current address: Thermodynamic Division, Istituto Nazionale di Ricerca Metrologica, Strada delle cacce, 91 10135 Torino, Italy