WEC Projects, in conjunction with its partner, Multotec, has designed and custom engineered a wastewater treatment plant for a gold mine in Mali, West Africa.

The plant, used to remove arsenic from the mine’s wastewater stream, incorporates a modular design which simplifies the logistics and reduces the costs of transport and installation, according to WEC Projects.

The international mine operator is a client of Multotec, an engineering company specialising in mineral processing plant design and installation. The company approached WEC Projects, a local EPC contractor in the water and wastewater treatment industry, to jointly develop a customised solution to remove toxic arsenic from the mine’s wastewater. A multi-stage removal system was required to meet the strict standards for the mine’s discharge. However, the system also required a modular design which would facilitate the transportation, installation and commissioning of the plant.

Wayne Taljaard, Managing Director of WEC Projects, said: “The mining industry in Africa presents some very unique challenges, not the least of which are the remote locations of many of the mines and the difficulties experienced in getting staff and equipment to sites where road, power and water infrastructure is often lacking, hence the requirement by Multotec for a modular solution that would allow for rapid transport to site and to simplify its installation and commissioning.

“The COVID-19 pandemic added to the difficulties for us and the client, causing delays that reduced the time frame for delivery.”

In the treatment process, the mine’s wastewater undergoes primary solid/water separation using coagulation and flocculation and the primary clarifier. From there it enters a two-stage chemical precipitation and secondary clarification process to reduce the arsenic levels. The final stage sees the sludge undergo dewatering before disposal. The treated water, although not potable, is then reused by the mine for process applications.

The plant has a processing capacity of 150 cu.m/h and is capable of reducing the arsenic levels from around 13 mg per litre to less than 0.1 mg per litre.

Taljaard added: “The project, incorporates a number of unique features in addition to its modular design, including nine custom-designed, proprietary lamella clarifiers and a multi-stage arsenic removal process capable of treating the wastewater to the mine’s discharge standards. WEC Projects has completed a number of water and wastewater treatment projects throughout Africa. Our ability to provide a customised and modular solution for Multotec underscores our ability as a major player in the industry both in South Africa as well as across the continent.”