Analytical Instrumentation & Environmental Monitoring


South African technology used to treat acid mine drainage in Botswana

May 2002 Analytical Instrumentation & Environmental Monitoring

Gauteng-based water engineering experts Thuthuka Project Managers, who have been contracted to design and construct a number of mine pollution control systems for mines in South Africa, are now spreading their net wider into other African states. This is in line with the increasing emphasis today’s world is placing on environmental issues and the resultant responsibility that industries must take for the consequences of their emissions and discharges into the atmosphere, the earth and the water systems and oceans.

Jay Forder, Projects Manager at Thuthuka, is overseeing a project presently taking place in Botswana. Two-thirds of the country consists of the Kalahari Desert and about 30% of the country is set aside as game parks, including the world-famous Okavanga Delta wetland. Tourism is thus an extremely important source of income to Botswana. Mining, however, is also a significant player in the economy due to the country's reserves of diamonds and nickel/copper. As all mining operations will produce a certain level of pollution, it can be expected that the potential inevitably exists from time to time for a clash of interests within these two important economic money-spinners.

Water is a precious resource in Botswana's semi-arid climate. Nearly two-thirds of the country's borders are formed by rivers, though some flow only in the wet season. Botswana has low rainfall and even though there is a distinct rainy season, rains are sporadic and inconsistent. It thus becomes even more important to ensure proper pollution control of Botswana's watercourses.

BCL - a copper/nickel mining complex - is one of Botswana's largest private employers. The mine is situated in the east of the country close to Selebi-Phikwe. The town was itself originally established because of the mining interests in the area, and is otherwise remote from the country's main industrial and commercial centres.

Through the CSIR, Thuthuka Project Managers has been commissioned to design and construct an acid water neutralisation plant for BCL Limited to treat acid water from the tailings dam. The technology being used to neutralise acid leachates and acidic process water was patented by the CSIR, for whom Thuthuka is the licence holder for the implementation of the technology.

The neutralised water from the new plant will be returned to the mine concentrator, where it will be re-used, thereby reducing consumption of a scarce natural resource. The main function of the plant is to raise the pH of the acid water using granular limestone as the alkali rather than the far more expensive slaked or unslaked lime. The use of granular limestone allows for a substantial operating cost reduction. The technology is simple, effective, robust and cost-effective and has already been implemented by Thuthuka Project Managers on three South African sites as well as the Botswana BCL project.

Sulphate is also removed in a controlled manner in order to prevent scaling of pipework in the concentrator. Another important aspect is that the plant will continue to operate after mine closure to ensure that acid mine drainage is not released to the environment, nor to the Motloutsi river that flows through the Tuli Block game reserve and ultimately into the Limpopo, a major South African water course. The possibility also exists that the Tuli Block may ultimately become a trans-frontier park through mergers with private game areas on the South African side of the border, in line with current southern African conservation trends. The Kgalagadi Transfrontier Park (formerly the Kalahari Gemsbok National Park) on the South African/Botswana border is an existing example of this conservation direction, with more plans in the pipeline for the merger of the Kruger National Park with conservation land in both Mozambique and Zimbabwe.

In order to avoid environmental damage to the Tuli Block (and by implication, ultimately to Botswana's tourism industry) it is imperative to ensure that only neutralised mine water enters the river. Thuthuka Project Managers signed a contract with the CSIR in September 2001 and at the time of writing, had begun construction. Forder reported that the project is expected to have been completed by mid-April 2002.

He says: "The project fits perfectly with Thuthuka's main focus in the water industry, which is the treatment and reconditioning of water to acceptable standards before it is released back into the environment. It is also a good example of the CSIR's technology expanding into neighbouring countries.

Bill Pullen, MD, Thuthuka Project Managers

011 315 7376

billp@tpm.co.za




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