Over 29% of global population still do not have access to safely managed drinking water sources, resulting in close to a million death each year. The United Nations has identified as one of the sustainable development goals enabling the access to clean water and sanitation for all. On-site electrochlorination emerges as a promising decentralized treatment due to its small physical footprint, amenability, easy operation, and safety. Previous studies of on-site electrochlorination have demonstrated that disinfection by electrochemically driven technologies might become a vital solution for decentralized areas, but single-pass flow cell competitivity has been barely explored. The aim of this work was to investigate the effect of operating parameters such as cross velocity (1.3-11.9 cm s-1), current density (5-15 mA cm-2), chloride concentration in the influent (50-250 mg L-1) on different engineering figures of merit such as: generation of active chlorine species, and electric energy consumption. The desired outcome is to ensure disinfection while operating an engineered system in a single-pass using less than 1 kW h day-1 (i.e., the energy provided by a solar panel). Box-Behnken design was utilized to explore inter-variable impacts through mathematical modelling. Chlorine active species evolution (Cl2/HOCl/OCl-) as well yield of toxic oxyanions (ClO3-, ClO4-) were evaluated for different representative electrocatalytic anodes of Ti/RuO2, Ti/IrO2, and Boron doped diamond. The Ti/RuO2 was identified as the most suitable electrode for effective generation of active chlorine in single pass of 2.4 s of hydraulic residence time with negligible generation of ClO2, ClO3-, and ClO4-. The maximum electrical energy consumption of the cell at household level was 0.22 kWh d-1. Performance of on-site electrochlorination with using Ti/RuO2 anode in the flow cell showed that cross velocity is the most influential parameter. In fact, desirable concentration of active chlorine over 2 mg L-1 might be achieved even with drastic changes in chloride concentration through controlling the cross velocity. Effective disinfection of bacteria and virus was assessed under optimized conditions. Complete inactivation of E. coli and MS2 virus was achieved in short contact times after single-pass through the electrochemical cell. These experimental results may encourage advancement of electro-disinfection systems towards higher technology readiness level.

Electrochemical flow cell optimization for sustainable on-site decentralized electrodisinfection

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