A Three-Step System (Biochar and Sand Filtration with Chlorination) for Handwashing Wastewater Treatment and Possible Water Reuse in Rural Schools

School handwashing facilities in rural areas without piped water and drainage systems often discharge wastewater directly into the ground, leading to environmental contamination and loss of a valuable water resource, particularly in water-scarce regions. This study evaluates a decentralised three-stage handwashing wastewater treatment system combining biochar and sand filtration with chlorination. The integrated system effectively improved water quality by reducing turbidity, colour, suspended solids, nutrients, organic matter, and microbial contamination. While biochar and sand filtration provided substantial physicochemical treatment, chlorination was essential to ensure complete microbial inactivation. The treated water met several water quality standards for potable use (handwashing only) set by the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA) standards. Additionally, it complied with international guidelines for greywater reuse in toilet flushing, irrigation, and floor washing. This innovative water treatment strategy could help clean and reuse handwashing wastewater on-site. This could provide rural schools with clean water to support water needs in water shortage periods, such as hand hygiene, garden irrigation, toilet flushing, and floor washing. Overall, integrating biochar and sand filtration with disinfection could help remote rural schools recover water, advancing towards the achievement of the Sustainable Development Goals (SDG) for good health (SDG 3), clean water and sanitation (SDG 6), and sustainable communities (SDG 11).