The total amount of mining wastewater produced globally has not been accurately calculated, but mines are estimated to produce hundreds of millions of tons of wastewater each year. Mining wastewater, if left untreated, can cause a wide range of detrimental effects including the pollution of groundwater and causing bioaccumulation of heavy metals in the food chain.
How mining wastewater is produced
Mining wastewater is produced from mining in a variety of processes:
- Mineral extraction and processing: Rock is excavated and crushed, then chemical and physical processes are used to concentrate the ore. Tailings, the waste from this process, is a mixture of water and rock slurry.
- Underground mining: When mining activities occur below the water table, groundwater needs to be pumped out to allow mining to proceed.
- Surface run-off: Rainwater falling on mine sites washes over exposed ore and mineral stockpiles, creating potentially toxic run-off
- Wastewater produced by mine personnel: Onsite mine personnel produce black and grey water that requires treatment prior to disposal.
When considering all of these potential sources of wastewater to design an onsite treatment system, the main contaminants requiring treatment can include suspended solids (usually in the range of 2 to 20 microns in size), heavy metals (including cadmium, copper, lead and arsenic), sulfates and other minerals (produced from processing sulfide containing minerals or from pumping out saline groundwater), processing chemicals (e.g. nitric acid, cyanide, solvents) and oils and grease (from mining equipment and through the use of ANFO for blasting).
Technologies used to treat mine wastewater
The type of treatment system required for a particular site will depend on what contaminants or combination of contaminants require removal from a mine site’s wastewater. Common treatment processes include:
- Chemical treatment (e.g. pH alteration and coagulation)
- Physical filtration (e.g. ultrafiltration or sand filtration)
- Desalination (e.g. reverse osmosis or evaporation)
- Adsorption (e.g. activated carbon and alumina)
- Biological processes (e.g. aerobic and denitrification systems)
- Passive treatment systems (e.g. constructed wetlands and site remediation)
Moerk Water are experts in designing treatment systems to treat mine wastewater. Contact us to learn more about how we can assist your specific mine wastewater issue.
