Abstract
Electrolysis of blackwater for disinfection and nutrient removal is a portable and scalable technology that can lessen the need for cities to construct large‐scale wastewater treatment infrastructure and enable the safe onsite reuse of blackwater. Several systems for treating wastewater from single toilets are described in the literature, but there are few examples of systems designed to use electrolysis to treat blackwater from nearby toilets, which is a situation more common in densely packed urban living environments. In order to scale a single toilet electrolysis system to one that could service multiple toilets, computational fluid dynamic analysis was used to optimize the electrochemical reactor design, and laboratory and field‐testing were used to confirm results. Design efforts included optimization of the reactor shape and mixing to improve treatment efficiency, as well as automated cleaning and salt injection to reduce maintenance and service requirements.Practitioner points Design of a reverse polarity mechanism to enable in situ electrode cleaning and improve long‐term electrode performance.Optimization of a hopper design and drainpipe location to collect and remove flaking precipitates and mitigate maintenance issues.Design of an automated salt injection system to guarantee sufficient chloride levels for producing adequate chlorine residuals for consistent disinfection.
Highlights
An estimated 4.2 billion people do not have access to properly managed sanitation systems (WHO/UNICEF JMP, 2019), which negatively affects their health and economic conditions, as well as the environment in which they live
Table salt (NaCl) addition The blackwater Electrical conductivity (EC) received from the CLASS system was relatively unchanged over the testing period with daily variations of ±300 μS/cm, properties differed between sites depending on the mineral content of the pour flush and the personal wash water sources used
The same was observed in this study: free and total chlorine concentrations after electrolysis increased rapidly as a function of EC after a threshold of 1,600 μS/cm in treated water was reached on site B (Figure 4a)
Summary
An estimated 4.2 billion people do not have access to properly managed sanitation systems (WHO/UNICEF JMP, 2019), which negatively affects their health and economic conditions, as well as the environment in which they live. 1 out of 10 persons do not even have access to a toilet and practice open defecation. This increases the likelihood of spreading diarrheal diseases and nematode infections (Prüss-Üstün, Wolf, Corvalán, Bos, & Neira, 2016) that are responsible for high rates of childhood stunting (Spears, Ghosh, & Cumming, 2013). In 2011, the Bill & Melinda Gates Foundation announced the launch of the Reinvent the Toilet Challenge (Kone, 2012). The intention of this Challenge was to develop technologies that would radically improve sanitation. The guidelines for the development of a Reinvented Toilet (RT) were that this RT:
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