Each heap leaching facility has its own system for dealing with the leachate that flows from the pad. While this material is rich in ore, it’s also still mixed with suspended solids and dissolved minerals that aren’t needed for the final product. Some facilities use only a single processing pond for treatment, but it’s common for two or more ponds to handle both pregnant solution storage and further processing. Then a second or third barren pond is needed to contain wastewater left behind after the ore is extracted. Pregnant, processing, and barren ponds represent the three stages of ore recovery. Slurry handling between the ponds must be done with care to prevent spills and leaks. This means that the solution channels used to transport liquids from one pond to the next must be lined as well. Of course, each type of pond also needs different lining considerations based on its features.
How Do the Ponds Vary in Design?
In general, all three types of ponds used on ore recovery sites are basically the same in design. However, they do have a few significant differences due to their intended uses. If there is a separate pond for pregnant solution that is not used for processing, it will need a chemical resistant liner but won’t have as much equipment installed in it. Processing ponds often feature aerators, agitators, and underdrains that must penetrate through the lining material without causing leaks. This means the material must be chemical and tear resistant at the same time. Barren ponds have the least demanding wastewater mixtures stored in them. However, the liquids and solids within them usually remain the longest, with some barren ponds doubling as permanent storage as a buried pit. That means these ponds need liners with the longest possible lifespan to ensure leaks don’t develop long after the facility is closed.
Pumps vs Gravity Fed Flow
It’s best to avoid pumping liquids from one pond to the next whenever possible during ore recovery. This is due to the viscosity and abrasiveness of the slurry produced during ore processing. These specialty pumps still eventually wear out too, leaving you investing in expensive replacements just to keep the process moving. Gravity fed ponds systems, relying on lined solution channels to connect them, are far more affordable to operate and easier to maintain. While clogs can still occur, it only takes a little manual labor to clear away silt or trash rather than the replacement of entire units of equipment.
Reusing Solution for Further Processing
Barren ponds can be built to temporarily hold the solution for processing back through the leaching pad or to permanently contain waste at the end of the cycle. Ponds for temporary storage only should be shallow and easily accessed, while permanent basins are built as deep pits that can be capped with impermeable covers and thick layers of soil. Even the tailings left over after processing are often valuable for reuse if any ore was left behind due to a reduced recovery rate. These materials should be stored at the surface until they’re depleted through multiple cycles of processing.
The amount of processing required for a particular ore will largely determine how many ponds are needed and how the steps are divided between them. Mines producing a smaller amount of raw material to process this way may only need a single pond, or two ponds, to separate pregnant and barren solutions. Large facilities with multiple targeted ores or minerals may need a dozen or more different ponds for a complete processing system. No matter how many ponds you need to build or what you plan to use them for, BTL Liners has the materials you need to complete the project.
