Windhoek, Namibia

How Windhoek taps water from sewage

For obvious reasons, sewage is unappealing and drinking it, completely unfathomable. Yet, while most of the world is still debating if you should even try to treat household sewage to drinkable standards, Windhoek has been tapping water from it for decades.

In 2018, Namibians marked the 50th anniversary of the first direct potable (drinking-quality standard) reuse plant in the world, the Goreangab Water Reclamation plant. In fact, it’s so successful, a second was kicked into action in 2002. The New Goreangab Reclamation Plant now puts improved water treatment technology into practice. In general though, there are three ways to tackle sewage treatment – all of which are becoming more common.

Different ways to tap from sewage

The first, is direct potable reuse. This is when sewage is treated to drinking-water standards and fed into the water distribution system. This is what is happening at Windhoek. The process has been taken up in other countries, including South Africa, where a water reclamation plant was constructed in Beaufort West.

The second is indirect potable reuse. Here, treated sewage is released back into natural systems like rivers to mix with water. Then, it is abstracted and treated to drinking standards. They do this in Singapore during droughts.

The last option is treated effluent reuse. For this, sewage is treated, but not all the way to a quality that makes it fit for drinking. The water is then used for stuff like irrigation or industrial use. This is also happening in South Africa, both in Cape Town and in Durban.

The Durban Water Recycling Project (commissioned in 2001) treats effluent and industrial wastewater to near drinking quality standards, and then sells it to industrial customers to use in manufacturing processes. The so-called sewage-to-clean-water plant can reportedly free up enough drinking water for about 300 000 people.

All three options can make a huge difference to the water security of a town, city, and country. Windhoek is a perfect example.

Why dry Windhoek looked to wastewater

Namibia, of which Windhoek is the capital, has the dubious distinction of the country with the lowest average rainfall in Southern Africa. Droughts are common, and in general, water is scarce. For decades already, all naturally available water sources in the centre of the country (where Windhoek is located) have been tapped to the max.

The city is committed to exploiting the maximum amount of water from all sources it has available. In Windhoek, every drop of water counts. Even the moisture in sewage cannot be allowed to go to waste.

A new water source is born

The reclamation plant was brought into operation in 1968, following severe water shortages before the extension of the state water supply scheme could be completed.

The plant is fed from two sources, the Gammams Sewage Treatment Plant and the Goreangab Dam. The plant can be split into two streams. One stream is to treat effluent from the sewage treatment plant and the other for the treatment of Goreangab Dam water. The raw waters can also be blended and treated as a single stream.

Another serious drought in 1997 led to the construction of the second plant, to cater for the ever increasing demand for water. The new plant applies all the best practices and lessons from the first plant. This old one now treats water to irrigate parks and sports fields but, since it began in 1968, nobody in Windhoek has ever gotten sick because of the water it produced.

Still turning your nose up at sewage?

The treatment of wastewater to the point where we can drink it poses extraordinary challenges. Yet, Windhoek is living proof that it is possible and even necessary.

As more international examples of sewage reuse for different purposes emerge, the case has already been made. With the correct technology and know how, our dirty water can be a new tap to help quench the thirst of cities of the future.

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