Electrochemical Disinfection of Biologically Treated Waste for Onsite Toilet Wastewater Treatment and Recycling: A Long Term Field Study

Abstract

The Closed Loop Advanced Sanitation System (CLASS) was designed to treat, disinfect, and recycle toilet blackwater from existing flush toilets in a multi-story apartment building. CLASS used a combination of biological pretreatment and electrochemical oxidation processes. Two systems were tested in two unique sites in Coimbatore, India for over 7,500 treatment hours (combined) resulting in more than 180 m3 of blackwater treated to stringent quality requirements based on ISO 30500.1 Nutrients and organic load from the toilet blackwater were predominantly reduced aerobically and anaerobically using either a Sequencing Batch Reactor (SBR, Unit A) or an anaerobic-aerobic biodigester (Ecosan, Unit B). The electrochemical treatment provided for the disinfection of pathogens in the blackwater as well as further removal of remnant organic load and nitrogen (Figure 1). The water produced by the system nearly met ISO 30500 effluent standards and was reused for flushing by the residents of the apartment building for 89 days.