ISABEL RUBIO ARROYO | Tungsteno
In 1968, Windhoek, Namibia, became the first city in the world to use recycled drinking water. Today, its example inspires other places: the Orange County Water District in California supplies more than a million people with safe recycled water, and Singapore, through its NEWater plant, produces recycled water for both industrial and household use. We explore the projects and processes that give every drop of water a “second life.”
How Namibia turns wastewater into drinking water
Namibia is one of the most arid countries in sub-Saharan Africa, and Windhoek sits on a plateau where evaporation is extreme: 83% of the rain that falls disappears into the air. The city lacks nearby perennial rivers and depends on water sources that fluctuate dramatically with the climate. Faced with chronic shortages and severe rationing in the late 1950s, the city had to look for innovative solutions.
In 1968, the Goreangab Water Reclamation Plant was established, using direct potable reuse. In other words, treated wastewater is fed directly back into the supply network without passing through a natural “buffer” such as a river or lake. Windhoek’s system is like an obstacle course for water: it must pass through multiple filters and treatment stages until it becomes completely safe to drink.
To keep pace with rapid population growth and rising demand, a new treatment plant was built in 2002. Today, the Windhoek system is a global benchmark and an example of sustainable water management, visited by experts from around the world. The plant produces up to 21 million litres of potable water per day. On average, the city’s drinking water contains between 20% and 25% recycled water. During periods of extreme drought, this source can provide nearly a third of the total supply.
Namibia has a pioneering project to convert wastewater into drinking water. Credit: DW News
A Giant in Drinking Water Recycling in California
There are other notable examples of water recycling. Orange County operates the Groundwater Replenishment System (GWRS) in California, recognised as one of the world’s largest water purification systems for drinking water reuse. Unlike Windhoek, which uses direct potable water reuse (to the tap), Orange County uses indirect potable reuse. This means that once the wastewater is purified, it is not sent directly to homes. Instead, it is injected or percolated into the county’s groundwater basins, where it mixes with the natural water supply before being extracted again for human consumption.
The system can produce up to 130 million gallons per day (about 492,000 cubic metres), enough to meet the needs of nearly one million residents, according to the Orange County Water District. This system supplies approximately 35% of the region’s total water demand and reduces dependence on imported water from the Colorado River or the Sacramento–San Joaquin Delta in Northern California.
This is one of the world’s largest indirect potable water reuse plants. Credit: Orange County Water District
The Water Revolution in Singapore
Singapore is also a global leader in water management. As an island nation with limited freshwater resources and little space for reservoirs, it faces one of the highest levels of water stress in the world. The NEWater process converts wastewater into ultra-pure potable water in three key stages: first, microfiltration and ultrafiltration remove microscopic particles and bacteria; next, reverse osmosis captures viruses, heavy metals, and chemical contaminants; and finally, ultraviolet disinfection eliminates any remaining microorganisms.
Singapore strives to manage its water safely. Credit: DW Planet A
At the heart of the system lies the Changi Water Reclamation Plant, which can treat up to 900 million litres of water per day. Because of the island’s limited space, much of the system operates up to 25 storeys underground, through a complex network of tunnels and tanks. The system relies on indirect potable reuse. Although the water is technically potable after treatment, most of it is used for industrial purposes—especially in the manufacture of microchips, which require extremely pure water—and for cooling systems. Only a small amount is pumped into reservoirs, where it mixes with raw water and undergoes further treatment in conventional plants before reaching homes.
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