An evaluation of the suitability of the limestone based sidestream stabilisation process for stabilisation of waters of the Lesotho Highlands Scheme

Abstract

A large proportion of the surface waters of South Africa and Lesotho, are soft and acidic, requiring stabilisation to prevent aggressive/corrosive attack of cement concrete/metal conduits, etc. The predominant control measure utilised by water utilities to prevent such attack is pH adjustment for calcium carbonate saturation control through the addition of lime or sodium alkali’s, and carbon dioxide. However, lime mediated stabilisation is expensive and progressively more so as the availability of high quality white lime suitable for water treatment is in short supply in South Africa, with the shortfall being imported at growing cost. Accordingly, a Water Research Commission project has considered the use of the limestone based Sidestream Stabilisation Process (SSP) process as an alternative for stabilising water of the Lesotho Highlands project. The SSP is achieved by taking a small sidestream of unstabilised water, dosing high levels of gaseous carbon dioxide (CO 2), and then contacting the CO 2-acidified stream with limestone.

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