Sludge and washwater management strategies for the Vaalkop water treatment plant

Abstract

The Vaalkop plant, owned and operated by Magalies Water, provides a valuable South African case study of sludge and washwater management at a large water treatment plant. Starting out as a small plant of 18 Ml/day about thirty years ago, it has steadily grown to a plant with treatment capacity of 210 Ml/day; fairly large by South African standards. During the preceding years, it has not only been subject to a vastly larger scale of operation, but it also had to adapt to a tremendous increase in the cost of raw water, an increased environmental awareness amongst water treatment professionals and general public alike, and a much more sophisticated and complicated legislative framework. It is the objective of this paper to track the sludge and washwater management practices adopted over the years at Vaalkop, and to present the current strategies adopted for the medium to long term. The paper will summarize the previous methods of sludge and washwater disposal, with reasons why they were adopted. The multitude of technical analyses and alternatives that were performed over the years will be summarized, and may provide valuable pointers for other applications in South Africa. The current system, which has just been commissioned, will be presented; its technical design parameters, the anticipated mode of operation, its costs and how the current environmental and legislative requirements are being met.