Windhoek’s water reclamation plant turns sewage into drinking water in a day.Credit: Margaret Courtney-Clarke
Namibia is the driest country in southern Africa, receiving an average of 280 millimetres of rain each year, 83% of which is lost to evaporation and a further 14% absorbed by plants. The country’s experience of dealing with water shortages has seen it become a model for others.
In 1960, Windhoek, its capital, struggled to support a quickly growing population. Increased demand put groundwater supplies under stress, and severe water shortages forced the city to innovate. After eight years of pilot studies, the Goreangab Water Reclamation Plant (GWRP) became the first in the world to produce purified drinking water directly from sewage water. Today, the plant produces up to 25 000 kilolitres of drinking water every day, or – up to 35% of the city’s consumption. It has also relieved the pressure on Windhoek’s groundwater supplies. “It was the best technology of the time,” says Troy Walker, associate vice president of Hazen and Sawyer, an environmental engineering organisation helping to deliver potable reuse projects in the United States, which has been under megadrought conditions since 2001. The Colorado River, which provides 40 million people with drinking water, is running at just 50% of its usual flow, forcing the states of Nevada, Arizona and California to sign a deal to jointly make drastic water-saving arrangements.
The fast-growing cities of the southwest United Stated must take less water from the river, and can learn from Windhoek’s 55 years of the safe practice of reusing what they already have.
Direct Potable Reuse (DPR)
Windhoek’s plant uses a process called direct potable reuse (DPR) which eliminates pollutants and contaminants from sewage water through a multi-barrier process before it is introduced as purified and safe water into the drinking supply, all within 24 hours. The model reintroduces recycled water directly back into drinking water supply, which decreases the time and distance between treatment and consumption.
The New Goreangab Wastewater Reclamation Plant (NGWRP), which replaced the original facility in 2002, does this by continuously maintaining a multi-barrier treatment sequence that blocks pathogens and other contaminants. This approach ensures that there are at least two, and in many cases three or more, effective removal processes – such as ozonation, carbon absorption, and membrane filtration, eliminating the risk of contamination.
The NGWRP was built in 2002, replacing the 1968 DPR facility (GWRP) to increase capacity following independence. That 2002 NGWRP is what still stands and operates today.
Thomas Honer, NGWRP general manager, says there are many contaminants in sewage water, from dishwashing chemicals to cosmetic preservatives, and that once his team finds them, they analyse, treat and remove them. “The most important rule is, and was, and always will be, safety first,” Honer says.
Windhoek local authorities claim that the plant has never been linked to a waterborne disease outbreak.
Other scientists, not involved in the plant, have often spoken about it as a positive model to follow. Stuart Khan, a professor of environmental engineering at the University of New South Wales, who specializes in advanced water treatment processes, says: “It was successful in providing a sustainable resource for Windhoek, and successful in setting an important precedent for other countries to follow”.
Windhoek provides a model for 55 years of data and evidence of safe practice. The data from Namibia helped convince regulators in the US that the practice is safe, and assuage public concerns. It has also provided a model for success for the engineers involved.
A global resource
In recent years, delegations from France, Germany, India, Australia, Singapore, the United States, the United Arab Emirates, South Africa and Mozambique have visited Windhoek to tour the NGWRP. Interest in the facility has grown along with water scarcity concerns. According to the latest UN World Water Development Report, the global urban population facing water scarcity is projected to double between 2016 and 2050, impacting up to 2.4 billion people worldwide.
Last June, construction limitations were imposed in Phoenix, Arizona, after determining that there was not enough water to support new housing divisions. Now, the city has announced plans to build a DPR facility to protect its groundwater supplies and establish a water source independent of the Colorado River. The new plant could treat 280 000 kilolitres per day, which can supply water for about 200,000 new households per year. Walker has helped to develop Arizona’s DPR regulations, and he visited the Windhoek facility in 2022 for inspiration. “It was about being able to see the success of their system, and then looking at some of the technical details and how that might look in a US facility or an Australian facility,” he says. “[Windhoek] has helped drive a lot of discussion in industry. [Innovation] doesn’t all have to come out of California or Texas.” Aleks Pisarenko, director of plant operations and maintenance services at Trussell Technologies, worked on a project to demonstrate the feasibility of DPR in San Diego, California, using Windhoek as a reference point. “It’s great to have a functioning success story as it helps with public acceptance and adds confidence that potable reuse can be done safely,” he adds.
Following Namibia’s lead, the US will have its first direct-to-distribution’ DPR facility in El Paso, Texas where, like Namibia, the recycled water will be distributed directly back into the drinking water supply. The city will turn up to 45 460 kilolitres of wastewater into high-quality purified drinking water, making it the biggest of its kind worldwide. Alongside Phoenix and San Diego, Los Angeles is also considering a DPR/IPR hybrid facility that will deliver 1 045 600 kilolitres a day.
Christina Montoya, a spokesperson for El Paso Water, says she has used Namibia as an example to help bring the people of El Paso on board with a new facility in Texas.
Windhoek’s record in obtaining regulatory approval and mitigating public concerns, experts agree, was invaluable, especially that there had been pushback on similar facilities in the US in the 1990s. Critical slogans, such as ‘toilet to tap,’ have historically eroded public support, and created a stigma around drinking recycled water.
