Design and preliminary implementation of onsite electrochemical wastewater treatment and recycling toilets for the developing world

Abstract

Self-contained toilet wastewater treatment system prototypes based on electrochemical oxidation of feces and urine using bi-layered semiconductor anodes ([Bi₂O₃]_z[TiO₂]_1−z/Ir_xTa_yO₂/Ti) have been designed, constructed, and implemented in regions where access to proper and sufficient sanitation is limited. Prototypes were designed to fit in shipping containers in order to provide toilets and onsite wastewater treatment with clean water recycling. Units were designed to handle the waste of 25 users per day (or 130 L of toilet wastewater). The first prototype was tested on the Caltech campus (Pasadena, California) followed by improved second-generation prototypes that were subsequently installed in India (Ahmedabad, Gujarat and Kottayam, Kerala) and China (Yixing, Jiangsu) for open use in various public settings. The prototypes were able to provide for the disinfection of pathogens (<10 MPN Total coliforms and <1 MPN Fecal coliform indicator organisms per 100 mL), reduction of chemical oxygen demand (<100 mg O₂ L⁻¹), ammonia (<10 mg N L⁻¹), and color at an average energy consumption of less than 180 W h per user per day. The treated wastewater was recycled for use as toilet flushing water.