Effects of process factors on the performance of electrochemical disinfection for wastewater in a continuous-flow cell reactor.

Although electrochemical disinfection has been shown to be an effective approach to inactivate bacteria in saline water, the effects of process parameters and reactor design for its application in low-salinity water have not been well understood. In this study, factorial experiments were performed to investigate the direct and confounded effects of applied current (5-20 mA), contact time (2.5-20 min), anode surface area (185-370 cm2), and chloride concentration (50-400 mg L-1) on the disinfection efficiency in fresh water and the secondary effluent of municipal wastewater. An electrochemical disinfection reactor cell with an internal volume of 75 cm3 was designed and fabricated. Residence time distribution analysis showed that the internal mixing of the reactor is similar to that of a dispersed plug-flow reactor. All studied process parameters showed significant effect on the kill efficiency, with the applied current and contact time having the most dominant effect. Although the effect of chloride concentration, which is responsible for electrochemical production of free chlorine in water, is statistically significant, it is not as prominent as those reported for high salinity water. A synergistic effect between chloride concentration and anode surface area was identified, leading to high kill efficiency (99.9%, 3 log kill) at low current density (0.0135 mA cm-2). Response surface modeling results suggested that a scaled-up disinfection reactor can be designed using large anode surface area with long contact time for high chloride water (400 mg L-1) or high current density with short contact time for low chloride water (50 mg L-1). The power requirement of a portable system treating 37.85 m3 day-1 (10,000 gpd) of municipal wastewater was estimated to be 1.9 to 8.3 kW to achieve a 3 log kill, depending on the reactor design.