Image for This city turns sewage into drinking water in 24 hours. The concept is catching on

This city turns sewage into drinking water in 24 hours. The concept is catching on

As megadroughts grip countries across the globe, politicians are flocking to a tiny, desert-locked African city to learn the secret to its circular water supply

As megadroughts grip countries across the globe, politicians are flocking to a tiny, desert-locked African city to learn the secret to its circular water supply

Namibia is the driest country in Sub-Saharan Africa, and home to two of the world’s most ancient deserts, the Kalahari and the Namib. The capital, Windhoek, is sandwiched between them, 400 miles away from the nearest perennial river and more than 300 miles away from the coast. Water is in short supply.

It’s hard to imagine life thriving in Windhoek, yet 477,000 people call it home, and 99 per cent of them have access to drinking water thanks to technology pioneered 55 years ago on the outskirts of the city. Now, some of the world’s biggest cities are embracing this technology as they adapt to the harshest impacts of climate change. But Namibia leads the way.

How did this come about? In the 1950s, Windhoek’s natural resources struggled to cope with a rapidly growing population, and severe water shortages gripped the city. But disaster forced innovation, and in 1968 the Goreangab Water Reclamation Plant in Windhoek became the first place in the world to produce drinking water directly from sewage, a process known as direct potable reuse (DPR). 

That may sound revolting, but it’s completely safe. Dr Lucas van Vuuren, who was among those who pioneered Windhoek’s reclamation system, once said that “water should not be judged by its history, but by its quality”. And DPR ensures quality. 

This is done using a continuous multi-barrier treatment devised in Windhoek during eight years of pilot studies in the 1960s. This process – which has been upgraded four times since 1968eliminates pollutants and safeguards against pathogens by harnessing bacteria to digest the human waste and remove it from the water. This partly mimics what happens when water is recycled in nature, but Windhoek does it all in under 24 hours. 

Nowadays, Thomas Honer oversees the New Goreangab Water Reclamation Plant (NGWRP), a bigger DPR facility built in 2002 to meet the demands of an expanding capital city after Namibian independence in 1990. Honer’s cabin sits just metres away from the churning effluent of nearly half a million Namibians. They could be drinking it by tomorrow.

circular water namibia

Windhoek’s water reclamation plant turns sewage into drinking water in a day. Image: Margaret Courtney-Clarke

“We know that we have antibiotics in the water, preservatives from cosmetics, anti-corrosion prevention chemicals from the dishwasher,” Honer explains. “We find them and we remove them.”

Honer adds that online instruments monitor the water continuously, and staff ensure that only drinking water that meets World Health Organisation (WHO) guidelines is sent to homes. If any inconsistencies are detected, the plant goes into recycle mode and distribution is halted until correct values are restored. 

“The most important rule is, and was, and always will be ‘safety first’,” says Honer.  The facility has never been linked to an outbreak of waterborne disease, and now produces up to 5.5m gallons of drinking water every day – up to 35 per cent of the city’s consumption.

Namibians couldn’t survive without it, and as water shortages grip the planet, Windhoek’s insights and experience are more important than ever.

These ultrafiltration membranes help to remove bacteria, viruses and pathogens. Image: Margaret Courtney-Clarke

Interest from superpowers across the globe

In recent years, delegations from the US, France, Germany, India, Australia, Singapore, and the United Arab Emirates have visited Windhoek seeking solutions to water shortages in their own countries. 

Megadrought conditions have gripped the US since 2001, and the Colorado River – which provides 40 million people with drinking water – has been running at just 50 per cent of its traditional flow. As a result, several states including Texas, California, Arizona and Colorado are beginning to embrace DPR.

Troy Walker is a water reuse practice leader at Hazen and Sawyer, an environmental engineering firm helping Arizona to develop its DPR regulations. He visited Windhoek last year. “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 said. “[Windhoek] has helped drive a lot of discussion in industry. [Innovation] doesn’t all have to come out of California or Texas.”

Water should not be judged by its history, but by its quality

Namibia has also helped overcome the biggest obstacle to DPR – public acceptance. Disgust is a powerful emotion, and sensationalist ‘toilet to tap’ headlines have dismantled support for water reuse projects in the past. Unfortunately, DPR’s biggest strength is also its biggest weakness, as the speed at which water can re-enter the system makes it especially vulnerable to prejudice, causing regulators to hesitate“Technology has never been the reason why these projects don’t get built – it’s always public or political opposition,” says Patsy Tennyson, vice president of Katz and Associates, an American firm that specialises in public outreach and communications.

That’s why just a handful of facilities worldwide are currently doing DPR, with Windhoek standing alongside smaller schemes in the Philippines, South Africa and a hybrid facility in Big Spring, Texas. But that’s all changing. Drought and increased water scarcity worldwide are forcing us to change the way we think about water. 

Now, the US is ready to take the plunge, and in 2025, El Paso Water will begin operating the first ‘direct to distribution’ DPR facility in North America, turning up to 10m gallons of wasterwater per day into purified drinking water – twice as much as Windhoek. San Diego, Los Angeles, California, as well as Phoenix, Arizona are also exploring the technology.

circular water namibia

As water becomes scarcer in some parts, countries are looking to DPR for solutions. Image: Margaret Courtney-Clarke

Of course, DPR is not a silver bullet in the fight against climate change. It cannot create water out of thin air, and it will not facilitate endless growth. But it does help cities become more climate resilient by reducing their reliance on natural sources, such as the Colorado River. 

As other nations follow in Namibia’s footsteps, Windhoek may no longer take the lead after almost six decades in front.

“But Windhoek was the first,” Honer reminds me. “No one can take that away.”

Supported by the Center for Collaborative Investigative Journalism

Main image: Nate Hovee/iStock

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