System cleans 36,000 litres a day and removes about 99% of toxins for irrigation

Langrug’s Stiebeuel River was heavily polluted by sewage, chemicals and traces of drugs, leaving residents of the growing informal settlement without access to clean water or sewage facilities.

Since 2018 researchers from the University of Cape Town have built a nature-based treatment system on an abandoned wastewater site that uses stones, heat‑treated wood and sand, and runs off‑grid on solar power.

The project now treats about 36,000 litres of contaminated river water every day and the system removes around 99% of toxins; roughly 3,000 litres is held back each day to irrigate community vegetable gardens.

Water is pumped by solar power into a network of filtration cells where it filters slowly for about five days; large stones trap particles, biochar made by burning wood at 800C removes pharmaceutical residues and ammonia, and finer stones and sand absorb remaining pollutants.

The team say the treated water is suitable for irrigation but not for drinking, and they note the system is not intended to replace conventional municipal treatment for large towns or cities.