Sub-Sahara Mining & Industrial Journal
Industrial WATER & WASTEWATER

WEC Projects devises sewage treatment plant plan for Mothae diamond mine

WEC Projects, a South Africa-based EPC contractor specialising in water and wastewater treatment solutions, says it will soon complete the installation of a new WEC Model B packaged sewage  treatment plant at the Mothae diamond mine in Lesotho.

The mine is 70% owned by Lucapa Diamond Company and 30% by the Government of Lesotho.

Rudolf de Koning, Sales Representative at WEC Projects, says: “The mine lacked a sustainable sewage solution. Producing 60 cu.m of domestic raw sewage per day, Mothae utilised honeysuckers – sewage trucks – to dispose of the sewage at the nearest disposal facility, almost 130 km away. This was obviously a very costly method of sewage disposal. WEC proposed the installation of its Model B conventional activated sludge treatment plant with a daily capacity of 80 cu.m, which allows for future upgrading and expansions of the mine operations.”

The R3.2 million ($194,817) installation is a combined activated sludge and clarification treatment plant. Its modular design simplifies the logistics involved in transporting to the site and simplifies assembly as well as ensures a smaller overall footprint, according to WEC Projects. The Mothae installation also integrates a Wastemaster that includes screening, de-gritting and oil removal to cope with fats and oils present in the sewage which could adversely affect the aerobic process in the plant’s reactor. The Wastemaster removes the oils, fats and non-biodegradable material upstream from the treatment process. The plant will treat the mine’s grey and black water piped to the current septic system.

“Besides the high fat and oil levels, another factor which could affect the treatment plant’s effectiveness was the high altitude of the site which results in low, fluctuating temperatures,” de Koning explains. “The biological population growth occurs optimally at around 19°C and above. In order to ensure the proper ambient temperature is maintained, the plant will be assembled within a larger enclosed facility.”

In addition to making the mine more environmentally compatible through the effective treatment of its domestic sewage, the plant also reduces the costs of transporting waste to the nearest disposal facility, it says. Another consideration is that water availability reduces considerably in the area during the winter. The new plant can help the mine reduce its water consumption.

Thato Tsephe, Project Foreman at Mothae, says: “We worked closely with WEC Projects on-site to develop a sustainable solution. WEC Projects had previously installed a sewage treatment plant at the neighbouring Letseng Mine and it was that facility that encouraged us to approach them. What is critical for us, what is critical for us is to complete the civil works and installation and commissioning of the plant during the winter season with the harsh climate posing many challenges.”

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