Water Reuse

Namibia, Africa

Windhoek, Namibia

The first major project to utilize direct water reuse is located in Windhoek, the capital of Namibia. Windhoek is located in an area with many challenges to water quality and quantity. The climate in and around Windhoek is very arid and the city is surrounded by the Namib Desert and the Kalahari Desert. The city relies on both surface water and groundwater for water supplies. The surface water comes from the impoundment of ephemeral rivers. Challenges for the maintenance of these reservoirs include pollution in the surrounding basin, low recharge and high evaporation. On top of very little water resources to begin with, the population of the city has been increasing steadily over the past thirty years (at rate of 5% per year since 1990). Because of all these factors, the city was inspired to explore the option of direct water reuse.

Over 30 years ago, the Goreangab Water Reclamation Plant was constructed. This plant took in water from the city's wastewater treatment facility and augmented that with flow from one of the city's reservoirs. This plant lasted for its anticipated lifespan of approximately 30 years and was recently replaced by the New Goreangab Water Reclamation Plant (NGWRP). The NGWRP features a "multiple barrier" approach. This means that more than one approach is used to address each of the critical elements of water treatment. At least three barriers are used for microbial pollutants and at least two barriers are used for aesthetic conditions. In some extreme examples, several barriers may be used. For example, when treating for Crytopsporidium, ozonation, enhanced coagulation, dissolved air flotation (DAF), dual media filtration, ultrafiltration and chlorination are used. One interesting aspect of the Windhoek situation is that in the absence of any guidelines or standards for reclaimed water, the city had to invent their own standards with input from organizations like WHO, the EU and the US EPA.

While the science and technology required to operate and manage the NGWRP is extensive and sometimes complicated, perhaps the most important part of Windhoek's direct reuse is the public outreach. Extensive and long lasting public education campaigns have been undertaken ever since water reuse began. This includes advertising campaigns and education in public schools from a young age. These campaigns, in combination with an excellent water quality record, have been very successful in achieving public acceptance of the project. Citizens not only have exceptional confidence in their water supply, they even see it as a point of pride for their city.

Sources:
Pisani, Petrus L. Direct Reclamation of potable water at Windhoek's Goreangab reclamation plant. Desalination 188(2006) 79-88.
Lahnsteiner, J and G. Lempert. Water management in Windhoek, Namibia. Water Science & Technology. 55(2007) 441-448.