Following its successful expansion of the sewage treatment plant at the Lucara Diamond’s Karowe mine in Botswana, WEC Projects has secured further orders from the client, it says.

This time, it has been engaged for the design and construction of a sedimentation trap, tanker filling station and associated infrastructure, including storm water drains and fencing.

Karowe, where a 1174.76 ct, high-quality white gem diamond, the third largest found in Botswana, was recently recovered, is near the village of Letlhakane in the arid eastern Kalahari Basin where temperatures average 35°C. As a result, water is scarce, so much so that the Government of Botswana has imposed severe water restrictions on companies operating in the region.

WEC Projects originally designed and built artificial wetlands which the mine uses to treat its effluent, removing contaminants such as BOD, ammonia, suspended solids and heavy metals, to a standard for reuse as process water.

The new sedimentation trap will be used in the water recycling process of the mine’s drilling operations. The effluent is pumped from the underground drilling areas to a concrete trap and clarification unit where it is dosed with alum and a polymer to enhance the settling of the solids. The effluent overflows from the trap to the plant’s oil skimmer to remove floating oil. The system treats an average of 34 cu.m/d of effluent but can be expanded up to 150 cu.m/d, if required, according to WEC Projects.

The polished water is drawn from the tanker station and disinfected by dosing chlorine. Although the water is not suitable for human consumption, it is reused in applications such as dust suppression.

WEC Projects Contracts Manager, Ruan Kellerman, said: “This project is a fairly standard one for WEC Projects, except for the wetlands section which was certainly the largest of its kind we have undertaken. Our clients, many of whom are located in some of the driest and hottest areas of Africa where water is scarce, rely on us to come up with agile solutions for water reuse. We can provide solutions capable of treating water to process water reuse standards all the way up to potable standards.”