Namibia is one of the most arid countries in the world; crossed by the Kalahari and Namib deserts and bordered to the west by the Atlantic Coast, rainfall is virtually nonexistent. Although it is located in a greener area, its capital Windhoek is under constant water stress, with an average annual pluviometry of barely 300 mm, and aquifers that strong evaporation prevents from being refilled.
To cope with this extreme situation, this African country introduced an unprecedented solution back in 1968: recycling municipal wastewater for human consumption. Worldwide to date, this solution has only been deployed in Windhoek, Singapore and California’s Orange County (United States).
OPUS®II: recovering process water to restore natural ecosystems
The oil and gas company PXP has chosen Veolia and its OPUS®II technique to treat the effluent from the Arroyo Grande oil field in San Luis Obispo County in California. Veolia had been chosen in 2013 to design, build and operate a produced water recovery facility. OPUS®II, an innovative proprietary technology, is used to produce high-quality water. Performance and price guarantees are provided over the contract’s twelve-year period. In addition to the advantage of being compact, Veolia’s facility allows the company to boost its oil production while helping restore the local ecosystem. The treated water provides 25,000 barrels per day, which will be used in OTSG-type (superheated steam) steam generators for oil production, while 20,000 barrels per day are discharged into nature, helping augment rivers in a particularly arid environment. This technology makes it possible to increase the crude oil production capacity, improve water management, and protect the environment. It proves the wealth of the product offerings from Veolia, which was able to count on several of its subsidiaries to tailor the offering to PXP’s needs.
“Multi-barrier” technology
The city of Windhoek’s wastewater is treated in its Goreangab plant, which opened in 1968. Modernized in 2002-2003, it has since been run and managed by Windhoek Goreangab Operating Company (WINGOC), a consortium held 67% by Veolia and 33% by the WABAG group.
During this modernization phase, several innovative technologies were put in place – biofiltration and granular activated carbon filtration, along with a “multi-barrier” process – to remove four main elements from wastewater (physical and organoleptic elements, macroelements, microbiological and disinfection by-products). The combination of technologies, chemicals and filters makes it possible to eliminate pollutants and solids in order to produce clean and perfectly drinkable water.
“Drinking water production from wastewater is based on the multi-barrier concept,” explains Thomas Honer, WINGOC’s General Manager. “Domestic effluents are treated using activated sludge. They are then transported to the Goreangab facility where they are converted into drinking water.”
The water made fit for drinking is then mixed with other supply sources, such as reservoir water and underground water from aquifers.
A battery of controls
The drinking water produced by the Goreangab facility is constantly subject to quality controls, not only to ensure the safety of the sources but also to win the public’s trust. “Samples are analyzed in the laboratory every thirty minutes,” states Ludwig Narib, Strategic Executive for Infrastructure, Water and Technical Services for the city of Windhoek. In addition, there is a health risk management program linked to research projects. It includes advanced tests in terms of virology, parasites, toxicity, pesticides, algae toxins, etc., conducted by external laboratories. Last but not least, the plant has been entirely automated: “the quality of the water is continually tested thanks to automatic samplers that take samples that are then analyzed by an accredited laboratory. A final check performed by the city tests the end quality once the recycled water has been mixed with drinking water,” continues Ludwig Narib.
All this effort has now paid off: the capital has been able to significantly increase its water resources.
“At present,” says a delighted Ludwig Narib, “26% of the drinking water supplied to inhabitants comes from recycling wastewater.”
Combating water stress
Should Windhoek’s experience pave the way for many metropolises that are facing water shortages?
London and Tokyo are among the eight metropolises that are struggling the most to supply their residents with enough water. Just like Miami, Cairo, São Paulo, Beijing, Bangalore and Mexico, they are faced with climate or infrastructure challenges and are among the cities most exposed to water stress. In the United Kingdom, for instance, London must deal with the convergence of two phenomena: relatively low rainfall, scarcely 600 mm per year on average (less than Paris and half that of New York), and a drop in water resources from rivers and the water table.
For the past 50 years, the solution implemented in Windhoek has proved that it is possible to increase a city’s drinking water supply by recycling wastewater safely and responsibly. However, technology alone is not enough. Windhoek has successfully teamed it with a public awareness-raising and education campaign, a water usage control system to prevent it from being wasted, and efforts to eliminate leaks and reduce water consumption in public gardens.
KEY FIGURES
20 000 m3 : this is the volume of wastewater recycled each day by Veolia to supply Windhoek with drinking water.
26 % of Windhoek’s drinking water comes from the Goreangab plant.
1968 : creation of the Goreangab plant.
2003 : takeover of the plant’s running and maintenance by Veolia as part of a consortium.
2018 : 50th anniversary of Windhoek’s wastewater recycling facility.
