The Windhoek Goreangab reclamation facility was a pioneer in direct portable reclamation and is still the only commercial-scale operation in existence, as far as the author is aware. Windhoek has managed to perform applied research and the initial facility has been modified on several occasions since its humble beginnings in 1969 until the launch of a new high-tech plant in 2002. Windhoek and its Goreangab wastewater reclamation facility are well-known in any discussion of water reclamation from wastewater. Windhoek, Namibia, was the first city to use direct potable reuse.
This blog is going to dip our toes into the history of this water reclamation plant and how it has benefited the Namibian environment and community.
Innovations In Windhoek
The availability of both hot and cold water springs prompted the settlement of Windhoek. With the addition of wells in the region, exploitation of these sources increased as the settlement developed. As a result, the water table dropped, and the first municipal well was constructed in 1912. In an aquifer with a safe guaranteed output of 1.73 million cubic metres, 60 municipal boreholes were drilled between 1912 and 2004.
Until 1933, when the Avis Dam, with a capacity of 2.4 Mm3, was built, groundwater was Windhoek’s only supply of water. The catchment area of this dam is tiny, resulting in a low guaranteed production. Its largest contribution from 1962 to 1973 was barely 2.4 percent of Windhoek’s usage, and it sometimes couldn’t give any water at all. As a result, Avis Dam is now solely used for recreational reasons.
A second minor surface reservoir, the Goreangab Dam, was erected downstream from Windhoek in 1958, with a capacity of 3.6 Mm3, and a conventional treatment facility was established to treat the surface water from this reservoir to drinkable standards. To deal with the city’s household and industrial effluents, the city opened its new 6,800 m3 per day Gammams Sewage Purification Plant on a location near to the Goreangab Dam in 1960. These two waste streams were treated jointly until 1963, when Gammams erected a series of anaerobic and aerobic oxidation ponds, and the majority of the industrial effluent load was moved to these ponds for treatment. Following treatment, these waste streams were mixed and released to a dry river bed in the 1960s; the reclaimed water was not used for drinking or other uses. However, by 1967, the City was seriously exploring potable reuse of recovered water, and the Gammams Works was expanded to enable 14 days of retention time in the maturation ponds, so enhancing the quality of final effluent for eventual use as influential to a water reclamation plant.
The city’s population expansion, however, more than negated these advancements. Furthermore, the whole City, including its informal settlements, is located upstream and within the catchment of the Goreangab Dam, and its rapid expansion has resulted in pollution that has gravely harmed the reservoir’s water quality. In reality, the surface water runoff caught by Goreangab Dam is frequently of lower quality than the Gammams WWTP’s treated sewage, making it inappropriate for reclamation using the procedure indicated above.
The New Goreangab Water Reclamation Plant
It was clear that something needed to be done. Because the readily available natural resources had been fully utilised and demand control techniques had been successfully applied, extensive reclamation was the logical alternative to supplement supply. However, it was determined that upgrading the existing reclamation plant would not be cost-effective, and the prevailing drought at the time prevented the interim loss of production from the old plant; as a result, the City of Windhoek obtained loan financing from European Financial Institutions to construct a new 21,000 m3 per day reclamation plant on a site adjacent to the old plant. This facility, which was completed in 2002, can currently provide 35 percent of the City’s daily drinkable water needs.
Open To The Public
The public’s acceptance and faith in the purity of this water is perhaps the most crucial cornerstone of drinkable recovery. The most challenging task for anybody wishing to replicate Goreangab’s efforts in Windhoek would be to overcome water customers’ apprehensions about direct reuse for potable uses.
Windhoek can now include the maximum authorised 35 percent recycled water into its potable water mix at all times thanks to the new facility. The balance of the City’s potable water is sourced from surface water wherever possible. Boreholes that tap the underlying aquifer are the city’s emergency fund, utilised exclusively when surface water is in short supply. In a typical situation, 25 to 35 percent of the land would be recovered, with 65 to 75 percent of the surface being reclaimed. Borehole water might account for up to 23% of total consumption in times of stress, with another 35% coming from reclaimed water and the balance coming from surface water resources. Windhoek, of course, increases water demand management methods and drastically reduces use during times of water scarcity.
Windhoek residents have become accustomed to the notion of potable reuse as part of their water delivery system. In fact, they’ve learned to take pleasure in the fact that their city is, in many ways, the world leader in direct reclamation.
The new facility began operations in August 2002, and the City has signed a 20-year operating and maintenance contract with a private sector partner. The plant is presently closed owing to a breakdown of the oxygen generating system (PSA), however it produced high-quality water during its first year of operation.
Goreangab is an amazing example of a successful invention in a country with limited natural and financial resources. Windhoek is rightly proud of what it has accomplished in the face of natural hardship.
— Bronwyn Reynolds, Fizzin