New Sewage Treatment Plant for Lesotho Diamond mine

WEC Projects, a local EPC contractor specialising in water and wastewater treatment solutions, will soon complete the installation of a new WEC Model B packaged sewage treatment plant at the Mothae Diamond Mine located in the Maluti Mountains 214kms from Maseru, Lesotho. The mine is 70% owned by Lucapa Diamond Company and 30% by the Government of Lesotho.

The mine lacked a sustainable sewage solution. Producing 60m3 of domestic raw sewage per day, Mothae utilised honeysuckers – sewage trucks – to dispose of the sewage at the nearest disposal facility, almost 130 kilometres away. This was obviously a very costly method of sewage disposal. WEC proposed the installation of its Model B conventional activated sludge (CAS) treatment plant with a daily capacity of 80m3 which allows for future upgrading and expansions of the mine operations.”

Rudolf de Koning, Sales Representative, WEC Projects
The newly manufactured mild steel, epoxy coated Model B reactor with staircase and walkway for Mothae mine.

The R3.2 million 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. 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. 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”, explains de Koning.

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, saving the mine hundreds of thousands per month. 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.

“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.”

Thato Tsephe, Project Foreman, Mothae

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