Ore processing may be an environmentally friendly and energy efficient way to recover metals that would otherwise be lost. That doesn’t mean it’s completely without byproducts and residues that need special handling. At the end of the ore recovery process, there’s still plenty of materials left over to dispose of and reuse as possible. While reuse may work well for ore processing liquids when the facility is operating, that cycle ends once all the ore is recovered. The project managers must settle on the right way to deal with tailings and other residues long before the facility is ever built. Processing ponds, especially barren ponds, can play a role in permanent storage if designed with this use in mind from the start.
Wastewater Treatment or Disposal
No matter how much the wastewater is reused during the active mining and processing phases, some amount will be left behind at the end. There are a few different methods for disposing of this contaminated water. Deep well injection is a common treatment used for fracking and mining liquids, but it may not be available near an ore recovery site. Pit burial isn’t always a good choice for liquids due to the risks of leaks over time, but it may work if the wastewater is still mixed in with tailings and other solids. Mines built near wastewater treatment plants usually send the liquids there if they accept that level of industrial waste. However, these treatment plants aren’t available in all areas either. On-site treatment, in an open barren pond, is often the only reasonable choice for remote sites where wells aren’t an option.
Fines Created by Chemical Reaction
While the chemical leaching process is an effective one, plenty of tiny particles of unwanted minerals and rock are still carried along with the ore. This means that the bottom of pregnant and barren processing ponds alike slowly fill up with sediment known as fines over time. As active processing ponds fill up with fines and grow shallower, they can also lose their efficiency and develop slower rates of recovery. Dredging may be required in between processing cycles to keep the efficiency up. Make sure the liner in the processing ponds is designed to withstand that kind of mechanical wear and tear so that damage won’t interrupt the next cycle.
Goal Ore Recovery Rates
For metals that are easily extracted in a single stage, recovery rates for this kind of metallurgy are often 90% or higher. More resistant metals like nickel can take multiple rounds of processing to result in that amount of ore recovery. If a particular treatment doesn’t produce as much ore as expected from the first round of leaching and processing, it’s easy enough to empty out the pond and try a new chemical mixture or treatment technique. Tailings with a significant amount of ore left are usually set aside for future processing when new techniques arise to extract the rest of the valuable metals.
Reprocessing Opportunities with Careful Storage
If tailings will be reprocessed later or reused in any way, they’ll need proper storage before they can be delivered to their final destination. Allowing rainwater to run over the heaped material can cause runoff over the surface of the ground. Keep these dry materials covered with flexible materials like RPE or RPP to ensure they’re ready to use when desired. The cover also stops dry and dusty fines from blowing away and causing heavy metal contamination in the area, which can be as much of an environmental problem as runoff or seepage.
Finding a Final Disposal Method
Tailings must be contained in the end after all the additional processing is completed. Once the maximum amount of ore is recovered, some kind of burial is usually used to deal with the resulting dry waste. Barren ponds used for holding wastewater in its last stages of processing are sometimes repurposed as direct burial pits, but they have to be built for this purpose from the start. They also need more durable liners than usual if put to that use. Other options include sending the tailings to a hazardous waste landfill or reusing them in projects like alternative cement products.
Tailings and wastewater don’t have to be a hazard if the right pond lining materials are used. Liners must be able to handle both short and long-term storage in order to prevent environmental damage. Secure your wastewater and tailings at all stages of processing with RPE geomembranes from BTL Liners.
