WEC Water has recently completed a wastewater reticulation and water treatment plant for a gold mine in Burkina Faso. This project builds on WEC Water’s comprehensive experience with water and wastewater treatment in West Africa.
WEC Water was appointed by the mine to conduct an audit of the existing wastewater handling facilities at the mine in February 2023 in anticipation of a planned pit expansion, which would result in an increase in the number of personnel in the area. At the time, the mine was using tanker trucks to remove sewage from seven collection points, including the camps and other operational locations. This method presented the following challenges:
- Increased operating expenditure due to rising diesel costs;
- Undesirable traffic entering the mine area;
- The risk of sewage storage facilities overflowing, resulting in malodours and disease vector attraction; and
- Loss of reusable water in dry regions.
WEC Water’s objective was to find a long-term solution to treat the sewage at the mine and reclaim water for use as dust suppression and irrigation, reducing the demand on potable and rainwater reserves. Our solution consists of the following three main components:
- A collection and pumping system that directs sewage to a new, centralised wastewater treatment plant;
- Biological treatment of 60-100 m3/day of wastewater to reduce COD and nitrogen; and
- A lagoon to store the treated water before re-use.
The sewage treatment plant (STP) was designed by our team of specialist process and mechanical engineers to meet the required discharge standards using a modified Ludzack-Ettinger treatment process. As such, the plant utilises an activated sludge system with nitrogen-reducing capacity.
3D model of the wastewater reticulation and water treatment plant, designed and completed by WEC Water, for a gold mine in Burkina Faso.
During the process, the wastewater is pumped through an upfront screenings box and then enters a concrete buffer tank designed to contain peaks and avoid overloading of the biological reactor.
The bioreactor, specifically designed by WEC Water, is comprised of two zones – the anoxic- and aerobic zones – and includes an integrated clarifier. The screened wastewater is pumped into the anoxic zone of the reactor where a submersible mixer maintains constant mixing of the anoxic mixed liquor. An air-lift pump transfers mixed liquor to the aerobic zone, which induces the A-recycle for nitrogen removal. Air diffusers, fed by blowers, drives air into the reactor to maintain the biological oxidation and continuous mixing effect. Sludge recirculation retains healthy sludge in the system and periodic wasting to drying beds ensures a consistent sludge retention within the reactor. Aluminium sulphate is dosed during the process to enable compliance with local phosphate limits and disinfection is achieved by dosing a hypochlorite solution into the clarifier overflow before entering the chlorine contact tank. Once disinfected, the treated effluent is stored in a lagoon for subsequent reuse as dust suppression, irrigation water or for safe environmental discharge. Nigel Birchall, Senior Contracts and Project Manager at WEC Water, says:
“One of the major challenges of this project arose due to the mine’s remote location. This required considerable logistical expertise to ensure the safe delivery of the complete plant to site without damage. The packaged design of the plant simplified the process as most of the plant was built within the footprint of standard shipping containers.”
Several WEC Water personnel were on site during the construction and commissioning phases of the project including process, mechanical, and commissioning engineers, who provided oversight during the installation phase and ensured the plant was successfully installed and commissioned. We are pleased to have completed this project and look forward to working with the mine again.
