Drinking water electrochlorination in a single-pass biomimetic flow cell with zero salt dosing

Abstract

Electrochlorination is an efficient and cost-effective treatment technique to provide safe drinking water in remote locations. Commercial electrochlorinators normally rely on the replenishment of salts to generate the disinfectant. In this work, a novel undivided electrochemical flow cell with affordable electrode materials (graphite and stainless steel) is proposed, simulating the chlorides naturally present in groundwater sources (25–250 mg·L^–1). The biomimetic 3D-printed flow field allows to generate chlorine in a single pass with residence times lower than 1 min. Parameters controlling the electrochlorination are evaluated through a definitive screening design and include applied current, flow rate, and concentration of ions, such as chloride, sulfate, bicarbonate, and calcium. The main factors influencing free chlorine are chloride concentration, applied current, and water inlet flow rate. These significant parameters are further studied and optimized in a Box–Behnken design, obtaining free chlorine concentrations higher than 0.5 mg·L^–1 in all evaluated chloride concentrations, with a maximum of 3.70 mg·L^–1 for the most favorable conditions. The optimal conditions for achieving the minimum specific energy consumption (SEC) while maximizing chlorine production were identified at a chloride concentration of 250 mg·L^–1, operating with a flow rate of 400 mL·h^–1 and applying a current of 35.5 mA. This setup resulted in the lowest observed SEC of 0.59 Wh·mg FC^–1. The favorable results for electrochlorination in this type of cell open up the possibility for scale-up, allowing processing at higher drinking water flow rates.

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ORCID for Luis Fernando Arenas: orcid.org/0000-0002-9579-5082

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