The catchment area of the De Bos Dam, which is the main water source for the Greater Hermanus area, experienced its most severe drought during September 2010 and April 2012. The dam content had dropped to below 18 per cent of its full supply capacity by May 2012.
In addressing this water shortage, Overstrand Municipality has developed a series of groundwater well fields to supplement the surface water being sourced from De Bos Dam. However, the groundwater being pumped is rich in iron and manganese, which must be removed to prevent problems ranging from the staining of fabrics to the clogging of the water distribution network with gelatinous bacterial organisms that use iron and manganese in their metabolism.
The Overstrand Municipality appointed Aurecon to provide engineering services to increase the water supply and treatment capacity of the Preekstoel Water Treatment Works (WTW), which involved integrating the treatment of the various well fields and designing a tailored process to ensure reliable achievement of target water quality.
A biological plant has been constructed adjacent to the existing plant at the Preekstoel WTW for treating a maximum of 10Ml/day borehole water. After an extensive period of monitoring and tweaking, the biology had established sufficiently to deliver treated water meeting the SANS 241:2011 quality requirements of such a plant.