R-008

Richard Webster

webster@ntu.edu.sg

Panyawut Tonanon

Nanyang Technological University of Singapore

Utilizing Electrolysis to Disinfect Pathogens in Water at Low Ionic Strengths

This study examined the practicality of using platinized titanium electrodes for electrochemical disinfection of Escherichia coli (E. coli) in water, focusing on the mechanisms involved in solutions with low electrolyte concentrations (ionic strengths between 1 – 10 mM). The inactivation of E. coli displayed a logarithmic decay trend, with no notable differences among the tested electrolytes (NaCl, NaHCO3, Na2SO4, NaH2PO4) apart from sodium chloride. The increased bactericidal effect observed with NaCl was linked to the formation of chlorine species. The uniform inactivation behaviour across various ionic strengths and bacterial concentrations indicates that reactive oxygen species (ROS) play a primary role in the deactivation mechanism, which is unaffected by the specific anion present, except for Cl–.

A comparison of three-electrode and two-electrode configurations demonstrated that the three-electrode system outperformed the two-electrode setup in achieving higher current throughput, which is essential for effective water purification in low ionic strength environments. This improved performance was credited to the potentiostat's capacity to mitigate solution resistance effects by incorporating a reference electrode with a stable potential.

These findings offer several practical applications, especially for small-scale water treatment in remote areas. The demonstrated effectiveness in low electrolyte environments highlights the potential for treating natural water sources without chemical additives. Additionally, the rapid disinfection rates observed with the three-electrode system make it a promising option for point-of-use water purification devices. Nevertheless, although the scalability of the three-electrode system appears promising, field implementation may face challenges, including the complexity of maintaining reference electrode stability during continuous operation and relying on a potentiostat rather than a simpler DC power supply.