WEC Projects, a South African EPC contractor specialising in water and wastewater treatment solutions, has completed the design, manufacturing, delivery, installation and commissioning of a new WEC Model B packaged sewage treatment plant for the Mothae Diamond Mine in Lesotho, handing over the plant to the client at the beginning of September 2022. The conventional activated sludge (CAS) treatment plant solves a problem for the mine – the offsite disposal of 60m3 of raw sewage generated by its operations every day.
“Prior to the new treatment plant’s installation, the mine was forced to dispose of its sewage waste using honeysuckers/sewage trucks to transport the sewage to the nearest disposal facility, almost 100 kilometres away. This was, understandably, an inefficient and costly disposal method.”Loreen Grobbelaar, Project Manager at WEC Projects
Overcoming the remoteness by using a packaged plant solution
The mine, located in the Maluti Mountains about 135kms from Maseru, is a partnership between the Lucapa Diamond Company and the Lesotho Government and began production in 2019, mining more than 30 000ct of diamonds in its first year of operation. Says Grobbelaar, “The mine’s relative remoteness made the logistics of transporting and installing a complete sewage treatment plant a challenge. However, the WEC Projects Model B plant is a packaged solution that incorporates a modular design with a small footprint. This made it much easier to transport to site, install and commission than other conventional treatment plants. We did encounter a few problems due to snowy weather and pump supplier delays but overall, we were able to complete the installation and commissioning of the plant on time.”
Supplying a full turnkey Model B sewage treatment plant
The Model B sewage treatment plant supplied to the mine is a combined activated sludge and clarification plant with a capacity to process up to 80m3 of raw sewage per day. An automated screening system inclusive of de-gritting and oil removal was installed upstream of the treatment system. In addition, the plant has been housed in a large facility to ensure that the correct temperature for optimal biological population growth is maintained (around 19°C) as it gets cold in the Maluti Mountains with large temperature fluctuations, particularly in winter.
WEC Projects was also contracted by the client to provide operations and maintenance services. To this end the company will provide the mine with quarterly audits of the treatment plant. A process engineer will travel to the site to take samples which will then be analysed by an accredited laboratory. WEC Assist, the operations and maintenance division of WEC Projects, will analyse the laboratory results which will allow for optimisation of the treatment plant by fine-tuning the process.
WEC projects also provided training for three of the mine’s operations staff during commission and will supply needed spares and consumables used in the sewage treatment process. Adds Grobbelaar, “The project was highly anticipated by the client who appreciated the efficient completion and the professionalism of all the WEC staff involved. WEC Projects are excited to continue this strong working relationship with Mothae Diamonds.”