Pretoria consulting engineering firm GFJ Consulting Engineers was awarded the contract for the design, project management and contract administration of the Vaalkop phase-five extension, which will nearly double the capacity of the Vaalkop water-treatment plant from 120 Ml/d to 210 Ml/d at Vaalkop dam.
The new pumping station at the plant will supply water to Rustenburg and surrounding areas.
The so-called southern supply scheme comprises construction of two 35 Ml reservoirs at Bospoort, and various pipelines, as well as a booster pumping station at Townlands, near Rus- tenburg, being undertaken by EVN Consulting Engineers.
The project follows an agreement signed between Magalies Water, Rand Water and the Royal Bafokeng administration in the North West Province.
The agreement stipulates that Magalies Water will deliver a peak supply of 85 Ml/d of potable water to the Rustenburg region. The project features fast-track design and construction, with only 24 months separating the signing of the agreement and the delivery of the first 25 Ml/d.
The new raw-water outlet from the Vaalkop dam and inlet manifold to the raw-water pumping station will ultimately be able to handle 360 Ml/d, explains Fenner.
In addition, the new raw-water pumping station is designed to integrate the existing pumping stations of previous phases.
The prechlorination facilities at the raw-water pumping station will also be upgraded to handle the lar- ger flows.
The raw water will be delivered to the new chemical building at the treatment plant through a new 600 mm glass-reinforced polyester pumping main, said to be a first for Magalies Water.
A new 90 Ml/d water-treatment plant at Vaalkop dam, with an ultimate capa- city of 120 Ml/d, has also been incorporated.
One of the greatest challenges was handling raw water from different sources, namely highly-turbid water from the Elands river, and clear water with a high algal content from the Crocodile river, reveals Fenner. After the first signs of blue-green algae had been detected in the raw water reaching the plant from the Rustenburg environment through the Hex river, a powder-activated carbon-dosing facility was added for the removal of tastes and odours expected to occur with the sporadic algal blooms.
The inlet in the new chemical building at the water-treatment plant divides the raw water into four streams, configured so that each stream can be dosed in a different configuration with lime, ferric chloride and polymer.
This allows operating staff to experiment with various dosing configurations simultaneously, as the quality of the raw water can vary greatly over short periods.
Upon completion, this will be the third-largest countercurrent dissolved air-flotation (Cocodaff) and filtration plant in the world.
Chlorine is then added to disinfect the clarified water before it flows into a 10 Ml/d clear-water tank, which serves both as contact tank and the sump for high lift, backwash and recirculation pumps.
After passing through the clear-water tank, the residual chlorine content is again adjusted to an exact figure, after which ammonia is added in a specific ratio to produce chloramines.
The high-lift pumping station will deliver a peak flow of 85 Ml/d into the pumping main to Bospoort 40 km.
Chloramines are used as a final disinfectant agent to ensure that a residual is maintained over the long pipelines, as well as to match the system used by Rand Water.
This is necessary as the treated water will mix with that of the water authority in the Rustenburg distribution system, explains Fenner.
Two 250 Ml sludge dams have also been added to the plant, while upgrading of the bulk power supply is being handled by Eskom.
The complete scheme is expected to be operational by December. The project will increase water availability over 350 km2, and will meet regional needs until 2010.