The sludge collected by the Actiflo®, will be processed in a vertical thickening unit to ensure that solids are reasonably dry, while still fluid enough to be pumped.
The clarified water, exiting the Actiflo®, flows under gravity to the Multiflo® unit where it will be coagulated again. The addition of lime, soda ash, magnesium chloride, and sludge recycle streams will reduce the scaling potential of the water. The softened water from the Multiflo® is then passed through three carbon filters, further reducing the water's organic content.
Following this, water will be treated using ultrafiltration (UF) with non-oxidising biocide, after which, reverse osmosis (RO) units will complete final polishing.
The brine produced by the RO plant is the final effluent to be disposed of in lined evaporation ponds. The permeate (cleaned water), generated by this plant, will be used in the Tutuka power station's cooling towers, ensuring minimal waste generation.
Pistorius says: "The result is that overall recovery of water is greater than 75%. This will reduce expenses associated with evaporation pond brine treatment and the power station's raw water intake."
The contract awarded by Eskom also requires that people from previously disadvantaged communities are trained in various fields of plant construction, including project management, site management, pipe welding, etc. "This project makes for ideal training opportunities, as the site has very specific challenges relating to available space, environmental conditions, and other challenges typical to construction on brownfield sites," concludes Pistorius.
Construction began in July 2011, and should be completed within four months.