The impact of informal settlement expansion on greywater generation: a potential missed opportunity?

South Africa is a semi-arid country with drought on the rise. The government reports that over 3,400 informal settlements exist nationally that both require potable water and generate greywater that could be treated and reused. The current study investigated this using the Zandspruit informal settlement in the Gauteng province of South Africa. Aerial photography graphic information system (GIS) layers of Zandspruit were traced in approximately 3-year intervals between 2000 and 2023, and drone photography was employed in 2022. Using survey data collected within the settlement, in almost a quarter of a century, the usage of potable water and generation of greywater have increased by over 730% to 575 and 400 m³ per day, respectively. More than 62% (248 m³) of greywater was reported as discarded daily outside around dwellings, foregoing any reuse potential. It is important to study how this wasted resource could be purified and reused to contribute to the water needs of the country, and to mitigate health risks and environmental pollution concerns within the community due to greywater exposure.