Researchers investigate wastewater reuse in Namibian town
A multi-year project in Namibia, headed by scientists from the Technische Universität Darmstadt, is looking for the best way to upgrade wastewater stabilization pond systems so the water can be reused to irrigate animal fodder crops.
Despite its simple aim, the project has the lengthy name of “EPoNa-upgrading wastewater ponds to generate irrigation water, using the Cuvelai-Etosha basin in Namibia as an example.”
Sewage Treatment Need Outstrips Capacity
The northern Namibia town of Outapi currently has a four-step wastewater treatment pond system. When it was being built about 12 years ago, most of the city’s 4,000 or so residents did not have access to sanitary services. Now about 5,000 residents of the growing town have sewage services, but the ponds are not designed to treat that much wastewater.
Jochen Sinn, a researcher with the Wastewater Engineering Research Group, Technische Universität Darmstadt, explained that the treatment system works by passing the wastewater through four ponds. The suspended solids sink to the bottom to be decomposed by microorganisms, then the effluent is naturally disinfected via sunlight. But, the system is overtaxed, which leads to repeated overflows.
Water Scarcity
The area is dry nine months of the year, so seasonal water scarcity makes it difficult to produce animal fodder. When not enough water is available for crops, livestock is slaughtered to resolve the issue.
The town council contacted Darmstadt’s Institut IWAR for help solving both challenges.
Dr. Susanne Lackner, head of the Wastewater Engineering Research Group at Institut IWAR, explained that the team is looking at changes to the current system. These include using different pretreatment technologies — a biological and mechanical treatment — and adding infrastructure such as guiding walls to help with flow control. Other improvements include filtering to address water quality. She summed it up:
It is about finding a simple way to upgrade the existing ponds so that the wastewater can be used to irrigate fodder crops. […] These basically known methods are being combined for the first time and adapted for use under the constraints that exist in Africa.
To best assess these changes, Lackner said researchers plan to leave one of two treatment lines in place to compare the effects of the modifications.
Treating Water for Crop Cultivation
Researchers from Hochschule Geisenheim University will evaluate irrigation and cultivation techniques to assess the most suitable low-cost irrigation technique and crops. The water treatment system is being designed to allow vital nutrients, such as nitrogen, to remain in the water to reduce the need for fertilizer or other soil amendments.
The team’s goal is to convert the entire plant so wastewater can be used for irrigation throughout the year.
Lackner added:
What is really exciting is that German wastewater treatment plants spend a lot of money and effort eliminating nitrogen and phosphorous from the wastewater, whereas here, we want to use them specifically for agriculture. […] Not only do we retain the resource of water itself, we also retain essential nutrients as fertilizer.
Best Practices
The research will look at the ecological, economical, and societal ramifications of the project, as well as its technical aspects.
The wider aim is to create technologies and best practices for wastewater treatment and water reuse that can be applied and easily replicated in other African nations. Sinn explains:
There has been only little exploration of the concept of reuse, i.e., recycling water, especially in arid countries. […] Water is a resource that is far too valuable to simply flush away.
In addition to scientists from Technische Universität Darmstadt and Hochschule Geisenheim University, researchers from Universität Witten/Herdecke and the Institute for Social-Ecological Research Ltd. are taking part. The project is intended to conclude in August 2019.
Additional information about EPoNa and the progress of the research is available online.
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