“The Aussenkehr Water Supply Scheme and water treatment plant is a testament to what can be achieved when a world-class water treatment plant needs to be built in even the most remote areas. The community of Aussenkehr now has access to clean drinking water thanks to the new infrastructure,” – Rainer Kaber, Aurecon Project Manager.
Aussenkehr is a farm on the banks of the Orange River in the south of Namibia. It falls within the Karasburg Constituency, borders on South Africa, and is one of the hottest and driest places in the country.
The mainly agricultural region is growing rapidly, with population studies showing that it will become the most densely populated area in Southern Namibia. The current population is estimated at 6 000 permanent workers on the farms, with this number increasing to around 30 000 farm workers during peak seasons. The inhabitants house themselves in huts that they build from river reeds and have been drinking untreated water from the Orange River, which poses a health risk.
In 2011, Namibian Government appointed Aurecon to design a bulk water supply system that would provide potable water to the people of Aussenkehr. The scheme consists of a river abstraction pump station, water treatment plant, intermediate storage reservoir and interconnecting pipelines, able to convey the water to the terminal reservoir, located at the future Aussenkehr town. Because water was being extracted from a run-off river, the team expected a high level of suspended solids in the water during flood times. The treatment process of the water plant was adjusted to handle this high silt load during the flood season to remove it from the water and provide water that is clean enough for the community to drink.
The water treatment plant was designed to have two sedimentation stages. The pre-sedimentation stage is designed for times of very high raw-water turbidity. The second stage was designed with a lamella settler, also known as an inclined plate settler. During construction of the plant, the plate settler was replaced with an inclined tubular settler, which offered further improvements to the plant’s operational efficiency. The plate settler was chosen for its small footprint, as the plant was located on prime agricultural land and thus it was important to optimise the space used.
The main challenge of the project was the remoteness of the site. Aurecon has offices in both Windhoek and Cape Town, but both are approximately 800 km from Aussenkehr. Delivering large infrastructure away from major centres led to cost implications and logistical challenges with contractors. To overcome this, Aurecon stationed a resident engineer on site during both the civil construction period as well as for the mechanical and electrical construction period to assist in the coordination between the Client, Contractor and local community. Ongoing collaboration between all parties helped the team achieve an innovative water supply scheme and treatment plant that will help bring real economic gain to the farmers in the area.
Aussenkehr is one of the best areas in the world to grow table grapes, with an increasing number of investors looking to finance and implement new table grape farms, as well as other produce. The number of farmers working in the region is expected to grow substantially and the new water supply scheme will contribute to their health, wellness and an improved quality of life.
“NamWater is pleased with the new water supply scheme at Aussenkehr and proud that this project will now bring potable water to the Aussenkehr Community which did not have access to clean drinking water in the past,” – Andries Kok, Namwater Water Supply South – Acting Chief Water.