Paarl, the largest town within the Drakenstein Municipality area, purchases the bulk of its water supply – approximately 95% – from the City of Cape Town. While it is good quality, the water is relatively expensive.
An existing water supply scheme included the Nantes and Bethel bulk storage dams sited on Paarl Mountain and the infrastructure to supplement the natural run-off to the dams with the Municipality’s allocation of water from the Berg River. In addition, reservoirs and pipelines existed to feed the water into the town's distribution network. This scheme could provide up to 25% of the town’s annual water requirements, substantially reducing water supply costs. However, apart from basic disinfection, no treatment facilities existed and the infrastructure was largely wasted.
The need for a treatment works was identified in a 2001 feasibility investigation by Ninham Shand (now part of Aurecon after merging with Connell Wagner and Africon in 2009). The Drakenstein Municipality subsequently commissioned the construction of an 8 Mℓ/d water treatment works (WTW) sited on Paarl Mountain.
The new WTW treats water from the two dams on the mountain, and is located on the boundary of the beautiful Paarl Mountain Nature Reserve. Due to its location, the plant was designed with careful attention to environmental considerations, whilst continuing the heritage of water supply on Paarl Mountain.
Aurecon designed an innovative treatment process that uses direct filtration to minimise the plant footprint. The filters are equipped with a dual-parallel lateral under-drainage system, the first plant in South Africa to incorporate this design. This system is part of an overall design to enhance the filter performance through the incorporation of optimised collapse-pulsing backwashing.
Other special design features included the architectural style of the WTW to minimise its visual impact. Granite sourced from excavations for the plant was used to clad structures, giving them a texture closely approximating that of their surroundings. Buildings incorporated ‘green’ roofs and the site was re-vegetated with indigenous seeds and plants from the mountain reserve.
Exceptional attention to plant design, construction and finishing, together with innovative solutions to environmental protection needs, has resulted in a special product that is intended to be a heritage for the community served by the Drakenstein Municipality.
The project was also honoured with no less than three industry-related awards which include: