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The Goreangab Water Reclamation Plant is the longest running direct potable reuse water reclamation plant in the world. It is situated in Windhoek, next to the Goreangab Dam in the Otjomuise suburb. It produces drinking water from the effluent of sewage of the City of Windhoek, without intermediate storage. Commissioned in 1968 it was the only plant of its kind. It retained that status for more than three decades.

Background[edit]

Namibia is the most arid country in sub-Saharan Africa. More than 80% of its landmass are desert or semi-desert. Its capital Windhoek, situated in the central Khomas Highland, has an average annual precipitation of 360 millimetres (14 in) and an average annual evapotranspiration of 3,400 millimetres (130 in). Potable water resources within 500 kilometres (310 mi) distance are all already utilised, and the city's population is growing annually by 5%.[1] Okavango, the closest perennial river, is over 700 kilometres (430 mi) away.[2] With the transportation of water economically not feasible, decreasing rainfall and increasing evaporation, extracting more and more water from the Windhoek Aquifer led to its overuse and consequently a dropping water level. By 1957 aquifer overuse had reached 57%, and a water crisis was looming.[3]

Obtaining drinking water from domestic sewage and particularly its blackwater components - human faeces, urine, and toilet paper - meets a psychological barrier in its users. This is even more prevalent in a direct potable reuse ("Toilet-to-tap"[4]) plant, where reclaimed water is immediately being fed into the potable water system. An indirect potable reuse plant is the more common procedure. In this case, treated wastewater is used to recharge an aquifer or fed into a river. This makes the water lose its "sewage identity"[2], even if the water is ultimately (e.g. downstream) used as potable water again. For the plant in Windhoek, though, negative public perception was never a problem.[5]

When it was commissioned in 1968 the Goreangab Water Reclamation Plant was the only direct potable reuse plant in the world, and it remained that way for decades.[6] In 2011 a second plant of this kind was built in in Beaufort West, South Africa,[7] and today there are three such plants in the United States and a plant in Malaysia, too. There is also a plant in Sydney, Australia, but did not start to operate due to public protests.[8]

History[edit]

The plant was built in 1968 to a capacity of 4,800 cubic metres (170,000 cu ft) per day.[9] Opened in 1969, it was not in daily use but operated about 8 months per year. Ammonia removal by adding chlorine and the use of active charcoal led to high operational cost in its initial years. By 1973 the utilisation had already dropped to 70 days per year.[10]

A redesigned process was started in 1976. Intended to make running the reclamation plant more economical, an ammonia stripping tower was added, the chemical dosage control was improved, and facilities were added to regenerate on site the active charcoal used.[11] Still, the cost of the reclaimed water far succeeded that of any other water source.[11]

In 2002 a second plant was built alongside the first as upgrading the old one would not have been economical. Since then, the maximum capacity is 21,000 cubic metres (740,000 cu ft) per day.[9] To distinguish the new plant from the old, it is referred to as the New Goreangab Water Reclamation Plant (NGWRP).

Technical description[edit]

Since the commissioning of the new plant, the original plant only processes water from the Goreangab Dam. Its effluent of around 1.3 million m3/a (46 million cu ft/a) is grey water, due to the dam's heavy pollution. It is used for the irrigation of the city's parks and sports fields.[12]

The capacity of the new plant is 7.5 million m3/a (260 million cu ft/a). As of 2007 the plant supplied 5.5 million m3 (190 million cu ft) of potable water, more than a quarter of Windhoek's demand.[12]

The entire process from inlet to outlet takes four days.[13]

Business structure[edit]

The Goreangab Water Reclamation Plant is operated by the Windhoek Goreangab Operating Company (WINGOC), whose business premises are on site.[14] WABAG, the designer of the 2002 plant, holds 30% of WINGOC.[15]

See also[edit]

References[edit]

Notes[edit]

  1. ^ Lahnsteiner & Lempert 2007, p. 441.
  2. ^ a b du Pisani, Petrus L. (November–December 2004). "Surviving in an arid land: Direct reclamation of potable water at Windhoek's Goreangab Reclamation Plant". Arid Lands Newsletter (56). Office of Arid Lands Studies, University of Arizona. ISSN 1092-5481.
  3. ^ du Pisani, Petrus (n.d.). "Windhoek Namibia: A Case Study in Water Supply in an Arid Environment" (PDF). City of Windhoek. Retrieved 5 September 2016.
  4. ^ "Welcome". Water & Wastewater Engineering. Retrieved 23 August 2016.
  5. ^ van Vuuren, Clayton & van der Post 1980, p. 671.
  6. ^ Law, I B (May 2003). "Advanced Reuse - From Windhoek to Singapore and Beyond" (PDF). Water. Water & Wastewater Engineering: 31–36.
  7. ^ Smit, Ellanie (27 August 2013). "Windhoek hailed for water recycling". Namibian Sun.
  8. ^ Kings, Sipho (11 March 2016). "Windhoek shows the world how to recycle sewage water". Mail & Guardian.
  9. ^ a b "Multiple Barriers Ensure Safe Potable Water From Reclaimed Sewage - Windhoek, Namibia". The Water Wheel (July/August). Water Research Commission, South Africa: 24–28. 2003.
  10. ^ van Vuuren, Clayton & van der Post 1980, p. 670.
  11. ^ a b van Vuuren, Clayton & van der Post 1980, p. 661.
  12. ^ a b Lahnsteiner & Lempert 2007, p. 442.
  13. ^ Tjihenuna, Theresia (22 August 2013). "Namibia to host water reclamation conference". The Namibian.
  14. ^ "History of the Windhoek Goreangab Operating Company". WINGOC. Retrieved 5 September 2016.
  15. ^ "Windhoek Goreangab, Water Reclamation Plant, Namibia". WABAG. Retrieved 8 September 2016.

Literature[edit]


source: https://en.wikipedia.org/wiki/User:Pgallert/Goreangab_Water_Reclamation_Plant

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