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RAPID URBANISATION of South Africa's population has resulted in significant pressure on water resources and treatment of wastewater. The 45 Ml Hartebeestfontein water care works (HWCW) is operated by East Rand Water Care Company (ERWAT) and serves the Kempton Park and lsando areas of Gauteng.
EARLY DEVELOPMENTS
Owing to the loss of the emergency dam to sinkhole formation on the site (figure 1), difficulties experienced with the operation of the short-sludge-age Pho-strip process employed at the plant, and high-strength industrial effluent received predominantly from the Kempton Park industrial region, ERWAT commissioned a study early in 2003 to investigate the feasibility of either upgrading the existing plant at Hartebeestfontein or decommissioning it and re-routing the effluent to the Olifantsfontein water care works (OWCW).
If the flow were re-routed to the OWCW, the latter works would have been near capacity with an additional ±35 Ml/day being required by 2010. The estimated cost of this extension would have been approximately R140 million. In addition, a by-pass outfall sewer would have to be constructed from Hartebeestfontein to Olifantsfontein.
Preliminary investigations indicated that the 10,3 km pipeline of between 1,2 m and 1,8 m diameter, with trench depths of up to 8-9 m in places, would have cost approximately R62 million in 2003 terms. A pumping solution would also have been possible at a capital cost of approximately R44 million. However, the annual pumping cost would soon have rendered this solution more expensive than the gravity pipeline option. Sludge handling problems would also have been experienced while the Department of Water Affairs and Forestry (DWAF) required the water from Hartebeestfontein to be discharged into the Rietvlei Spruit. If the HWCW were to be closed down and the water were to be treated at the OWCW, ERWAT may have had to return the water back to the Rietvlei Spruit. This would have required a pump station, and an 8,5 km pipeline at an estimated of capital cost of R27 million and an annual operating cost of ±R0,5 million. In addition, decommissioning of the plant at Hartebeestfotnein would have resulted in environmental aspects requiring attention at considerable cost. It was estimated in 2003 that the overall cost of this option would have been in excess of R230 million.
If the HWCW were...