Zutari designed and implemented a process based on biological oxidation and filtration to remove iron and manganese from the groundwater. This approach was chosen over conventional chemical precipitation methods. Although biological oxidation had been successfully demonstrated internationally, this was the first application of its kind in South Africa.

The raw water’s high concentrations of iron and manganese exceeded those reported in international case studies, making this project both pioneering and technically challenging. Despite this, the team identified biological treatment as the most viable and sustainable solution.

A new biological plant was constructed adjacent to the existing facility at the Preekstoel WTW, designed to treat up to 10 Ml/d of borehole water. After an extended period of monitoring and process optimisation, the system stabilised, and the biological process was able to consistently produce treated water meeting the South African National Standard (SANS 241:2011) for potable water quality.