Abstract
Electrochemical disinfection—a method in which chemical oxidants are generated in situ via redox reactions on the surface of an electrode—has attracted increased attention in recent years as an alternative to traditional chemical dosing disinfection methods. Because electrochemical disinfection does not entail the transport and storage of hazardous materials and can be scaled across centralized and distributed treatment contexts, it shows promise for use both in resource limited settings and as a supplement for aging centralized systems. In this Critical Review, we explore the significance of treatment context, oxidant selection, and operating practice on electrochemical disinfection system performance. We analyze the impacts of water composition on oxidant demand and required disinfectant dose across drinking water, centralized wastewater, and distributed wastewater treatment contexts for both free chlorine- and hydroxyl-radical-based systems. Drivers of energy consumption during oxidant generation are identified, and the energetic performance of experimentally reported electrochemical disinfection systems are evaluated against optimal modeled performance. We also highlight promising applications and operational strategies for electrochemical disinfection and propose reporting standards for future work.
Highlights
Waterborne pathogenic bacteria and viruses were responsible for an estimated 842,000 diarrhea related deaths due to insufficient water quality, sanitation, and hygiene in 2012.1,2 In combination with handwashing and other hygienic practices which reduce person-to-person pathogen transmission, water treatment reduces disease by decreasing pathogen transmission from the environment.[3−5] A significant source of pathogens in water treatment are due to fecal contamination from inadequate or improperly managed sanitation systems.[6,7]
Disinfection is typically carried out prior to potable water distribution or discharge of treated wastewater to receiving water bodies.[18−20] aging centralized treatment infrastructure has contributed to unsafe levels of pathogen exposure, such as recent Legionella outbreaks in the U.S, leading to increasing interest in distributed disinfection systems, wherein pathogen inactivation occurs at the site of water consumption or wastewater generation.[21−23] For most centralized water and wastewater treatment paradigms, pathogenic organisms are inactivated through the application of oxidants such as free chlorine, chlorine dioxide, chloramines, ozone, and ultraviolet (UV) radiation.[24−31] These oxidants are supplied from external sources (e.g., Cl2, NaOCl, ClO2, O3, UV irradiation) as a final stage during water and wastewater treatment.[25,32,33]
For the more commonly used electrodes in electrochemical disinfection, such as dimensionally stable anodes (DSA) and boron-doped diamond (BDD) electrodes, between 11% and 65% of charge passed leads to nitrogen oxyanion production, with greater amounts occurring at more oxidative potentials.[75,77]
Summary
Waterborne pathogenic bacteria and viruses were responsible for an estimated 842,000 diarrhea related deaths due to insufficient water quality, sanitation, and hygiene in 2012.1,2 In combination with handwashing and other hygienic practices which reduce person-to-person pathogen transmission, water treatment reduces disease by decreasing pathogen transmission from the environment.[3−5] A significant source of pathogens in water treatment are due to fecal contamination from inadequate or improperly managed sanitation systems.[6,7] In these contexts, open defecation or improperly sited sanitation interventions such as pit latrines leach wastewater and associated pathogens into onsite and downstream water supplies.[8,9] As of 2018 an estimated 4.5 billion people do not have access to safely managed sanitation services, almost 900 million of whom still practice open defecation.[10]. Little focus has been devoted to contextualizing the potential challenges of applying electrochemical disinfection systems in both water and wastewater treatment. This Critical Review explores the impacts of treatment context, oxidant selection, and operating practice on the reported and potential performance limits of electrochemical disinfection systems in terms of oxidant dose and electrical energy consumption. We propose reporting standards for future electrochemical disinfection studies and recommend pathways for future development
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