PROJECT MANAGEMENT: South Cape Keeps VWS Busy
Recent Western Cape Business News
VWS Envig has been kept very active in the drought-stricken Southern Cape, where its expertise in water management is being put to good use.
It has been awarded a turnkey contract to supply the Knysna Municipality with a reverse osmosis water augmentation plant. The plant will produce an additional two mega litres per day of drinking water for the town. The municipality appointed SSI Engineers and Environmental Consultants as their consultant and Keith Turner of the SSI Knysna Office is the appointed Engineer.
According to Abrie Wessels, VWS Envig general manager, Cape region, the project was fast-tracked due to the serious water shortage in the Southern Cape and the need for additional potable water.
The plant has been designed by the VWS Envig team in Paarl, with the heart of the plant consisting of three reverse osmosis skids. Standard Desalator D-710T skids were manufactured in its Spanish sister company’s workshop, part of Veolia Water Solutions & Technology, due to fast delivery times. The remainder of the system has been manufactured and procured from the Cape region.
“The skids were fitted with energy recovery turbines to utilise the energy in the brine and thus save on electricity consumption and reduce the carbon footprint of the plant,” says Wessels.
Raw water is sourced from beach wells near the Knysna lagoon and the plant was constructed at the Knysna Wastewater Treatment Works. This allows the new plant to take advantage of the existing infrastructure and blend the outfall from the conventional sewage treatment plant with the reverse osmosis brine. The blended water will have a salinity lower than that of seawater and thus the co-operation of the two plants is a major benefit.
The drinking water from the plant is pumped back into the existing Knysna potable water reticulation system with energy-efficient pumps.
VWS Envig will operate and maintain the plant for a period of three years for Knysna Municipality.
The company has also been awarded the tender by the Mossel Bay Municipality to upgrade and reuse treated effluent at its Wastewater Treatment Works (WWTW). The upgraded water will supply high quality process water suitable for production to PetroSA’s synthetic fuels plant near Mossel Bay.
“In its current phase and over the short term, this plant will enable the Mossel Bay Municipality to supply sufficient water to its customers during critical times such as these, and over the long term, it will relieve the ever increasing pressure on available water resources by purifying more effluent from the Municipality’s WWTW for specialised industrial and other purposes,” explains Cobus Olivier, engineering manager Paarl, VWS Envig.
VWS Envig will provide the mechanical and electrical works associated with the reuse plant. The treatment technology to be used is membrane separation by way of reverse osmosis. The main treatment steps are micro-screening (the micro-screens are supplied by VWS Envig’s international sister company, Hydrotech of Sweden), ultra filtration and desalination by reverse osmosis. This plant will be the first in South Africa to use this particular combination of treatment steps.
“The upgraded water, fed from final domestic sewage effluent having passed through the Mossel Bay WWTW treatment processes, will be pumped via a new pumpstation from the reuse plant at Hartenbos Sewerage Works into the existing rising main from the Wolwedans Dam that supplies the PetroSA synthetic fuels plant. The current capacity of the plant is five megalitres of water daily, but the intention is to increase capacity to 15 megalitres per day in the future.” VWS Envig will operate and maintain the plant for at least the first three years, with the option of an extension.
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