Direct potable reuse has been supplying drinking water to residents of Windhoek for decades, demonstrating how treated wastewater can be safely returned to the municipal supply at scale. Since 1968, the Namibian capital has operated a system that converts domestic sewage into potable water, producing up to twenty-one million litres per day.
Windhoek is widely cited as the world’s first capital city to implement direct potable reuse. The current facility, operated by Windhoek Goreangab Operating Company (WINGOC), treats approximately twenty-one thousand cubic metres of wastewater daily, equivalent to the same volume in litres, and feeds this water back into the city’s supply network.
The origins of the system date back to Oct 1968, when the municipality commissioned its first sewage reclamation plant in response to chronic water scarcity and limited natural resources. Decades later, the New Goreangab Reclamation Plant was completed in 2002, incorporating updated treatment technologies to expand capacity and strengthen safeguards.
From wastewater to drinking water
What distinguishes the Windhoek approach is not only its longevity but also the route the water takes. Instead of relying solely on rivers, reservoirs or aquifers, treated urban wastewater is used as an additional source of drinking water. After undergoing advanced treatment and continuous quality control, the reclaimed water is blended with other potable sources before entering the municipal distribution system.
Direct potable reuse refers to the practice of treating wastewater to a high standard and supplying it directly to consumers without using an intermediate environmental buffer, such as a river or lake, for storage or dilution. According to WINGOC, final disinfection and water quality adjustments are carried out before the reclaimed water is introduced into the city’s supply.
Climate pressure behind the project
The development of direct potable reuse in Windhoek is closely linked to Namibia’s climate. The country is among the driest in Africa, and the capital has long faced the risk of water shortages. Project documentation notes that the decision to build the original Goreangab reclamation plant made Windhoek the first city in the world to produce drinking water directly from municipal wastewater.
Treatment processes and safety barriers
The treatment process is designed around multiple barriers to reduce microbiological and chemical risks. In its current configuration, the plant uses treated secondary effluent from the city’s sewage treatment works as its sole source water.
Initial treatment includes oxidation with ozone and the addition of chemicals such as potassium permanganate and ferric chloride to support coagulation and microfloc formation. Slow flocculation follows, allowing particles to grow in size before separation by dissolved air flotation. During this process, fine air bubbles attach to the flocs and lift them to the surface for removal.
The water then passes through rapid gravity filtration using dual-media filters. Further pH adjustment and chemical dosing support the removal of iron and manganese. Residual waste streams from filtration and flotation are diverted to separate effluent treatment units.
Advanced polishing and disinfection
Subsequent treatment stages include a second ozonation step, which acts as both an oxidant and disinfectant. Ozone is generated on site, and any remaining ozone is neutralised using hydrogen peroxide.
Activated carbon filtration follows, combining biological activated carbon, where microorganisms degrade biodegradable compounds, with granular activated carbon to adsorb remaining dissolved organics and reduce the potential for disinfection by-product formation.
Ultrafiltration using membranes provides final polishing, removing fine particles, bacteria and viruses. The treated water is then disinfected with chlorine and stabilised through pH adjustment before being blended with other potable supplies and distributed across the city. WINGOC notes that chlorination also provides protection within the distribution network.
Monitoring and operational control
Operational oversight is a central feature of the system. Case studies describe continuous online monitoring, with data transmitted to a control room at frequent intervals. Distribution can be halted if any parameter falls outside defined limits. In addition to real-time monitoring, daily laboratory sampling forms part of routine quality control, and the plant operates on a continuous, round-the-clock basis.
Scale and public perception
At full capacity, the plant supplies drinking water to hundreds of thousands of residents. Institutional descriptions link the daily production of twenty-one thousand cubic metres to a significant share of Windhoek’s overall water demand.
Public interest in the project often centres on concerns about the origin of the water. As a result, official descriptions tend to emphasise treatment standards, multiple safety barriers and monitoring regimes rather than framing the system as an emergency or temporary measure.
However, publicly available information does not always present consistent data on costs, energy use or standardised efficiency metrics. This limits direct comparison with other water supply options in different cities and regions.
Source: CPG
