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R?Âssing desalination plant raises ire

Mon, 4 August 2014 04:30
by Memory Tjimbundu
Business




Environmentalists have raised concern over the proposed desalination plant to be erected by Rössing Uranium in Walvis Bay.
The desalination plant will be located six kilometres north of Swakopmund at the existing Swakopmund Salt Works. SLR Environmental Consulting Namibia and Aurecon Namibia have jointly been appointed to oversee the environmental impact assessment process.
Desalination is a process that purifies water by removing dissolved mineral salts and other solids from brackish or seawater, making it suitable for human consumption.
Although it is widely considered a positive move, a number of environmental concerns will however have to be addressed before the project can commence.
Rössing Uranium Advisor: Corporate Communications, Botha Ellis said that a number of questions around the social and economic impact will be addressed as part of the Social Environmental Impact Assessment before the project commences.
“The development of an additional source of water may have economic implications for other water users in the region. These potential impacts will be investigated by both economic and social specialists,” he said.
Of concern to many fishermen and beach lovers is the discharge of brine. Aquatic species have a tolerance for natural salinity levels, however if these levels undergo significant change this can be detrimental to these creatures.
In some instances chemicals are used to treat the intake water, which if released with the brine and can be harmful to marine habitats and receiving water environments, unless effectively mixed into the sea.
Desalination involves abstracting saline water from the sea and pumped to the plant. Reverse Oosmosis (RO) uses semi-permeable membranes and pressure to separate dissolved matter and salts from saline water. The desalinated or fresh water is then pumped to a storage facility for use.
Brine, the process waste, is about twice the concentration of seawater consisting of everything that is left behind during the process, and has a higher salt concentration than the input water.
Simply put, desalination takes a volume of sea water and returns a little more than half at an almost double salinity concentration.
Various specialists studies of the potential impacts associated with the discharge of effluent from the plant will be undertaken as part of the SEIA process, SLR Consulting said in a statement released last week.
The plant’s water intake will be in the vicinity of the existing Swakopmund Salt Works intake. To set up infrastructure to transport water to the plant, two alternatives are being investigated, a channel or a pipeline.
In terms of its impact on the shoreline environment, construction of water intake structures and pipelines to carry feed water and concentrated discharge may cause disturbances to environmentally sensitive beach areas.
Although the intake structures will be designed to maintain a flow of less than the minimum escape velocity for aquatic species, there is a risk of mortality of plankton, fish eggs and fish larvae when water is sucked in at the inlet areas.
This potential impact will also be studied by a marine ecologist, as part of the SEIA process.
The construction of the power line may pose a risk to local avifauna (birdlife) due to the increase potential for collisions to occur.
Changes to the existing surface water structures in the area may also impact the local faunal residents and migrants. An avifaunal specialist study will therefore be  undertaken.
According to a Rossing information circular, NamWater has been pursuing the development of a new desalination plant at Mile 6 (roughly 10km North of Swakopmund), but the outcome, timelines and commercial aspects to this project remains uncertain. In addition, an Agreement to secure water on a long-term basis from Areva’s desalination plant at economically feasible terms could also not be reached.
“Therefore, Rössing Uranium wishes to investigate an alternate source for desalinated seawater in an effort to reduce the cost of its mining operations and enhance its commercial sustainability”, states the circular.
Currently, Rössing Uranium purchases desalinated water for its mining operations at a significant cost. The Erongo Region is a water scarce environment, relying predominantly on the Omdel aquifer for its supply. Erongo region is also a centre for growth in Namibia and central to the country’s economic vitality.
As an interim measure, Rössing Uranium, along with other mines in the region, have been supplied with desalinated water from the Areva desalination plant near Wlotzkasbaken, since November 2013.