Some of the largest and most well-designed evaporation ponds in the world were built for the use of the mining industry. Gas, oil, metal, and mineral mining all involve evaporation ponds for one or more of the steps of extracting valuable materials from raw rock. Evaporation ponds for mining often share design features and functional details, but they may vary greatly in their intended use. Explore how the mining industry makes great use of evaporation ponds and how to optimize their design and operation.
Harvesting Valuable Materials
Instead of being primarily used for wastewater processing or storage, the biggest use of evaporation ponds in mining is for separating out valuable materials. Lithium, potash, and even sea salt is separated and concentrated for capture with the use of massive evaporation ponds. These materials can’t be sorted by magnetic or mesh screens, so instead they’re dissolved into water or settle at the bottom of the pond for easier harvesting. Some of the lithium and potash evaporation ponds built around the world are so large (and brightly colored) that they’re visible from space. Durable liners from BTL Liners are particularly essential for these processing evaporation ponds since they prevent the loss of the final product. Without a liner, metals and minerals that settle out of a pond will mix in with the mud or clay at the bottom and require extra processing.
Tailing ponds are some of the most well-known and common harvesting pits that rely on evaporation. Many mining methods still relying on powdered rock that is tricky to separate from minerals or metals. Yet, tailing ponds also generate highly acidic and contaminated wastewater. The majority of tailing ponds around the world are natural pits with no liner, leading to extensive soil and water damage in the surrounding area.
Containing Wastewater
The second most common use for evaporation ponds in the mining industry is for holding and reducing wastewater. Cutting the volume of water released by a hydraulic fracturing or natural gas operation by even 50% through evaporation can cut disposal costs significantly. If this can be combined with the previous use, evaporation ponds serve a double purpose to process both valuable products and cost-generating wastewater. Since wastewater generated by mining facilities is often rich in acids, caustic salts, heavy metals, and minerals, it can’t be contained in a naturally lined pond. Impermeable liners are essential for all mining evaporation ponds, regardless of the specific use for them.
Holding Water for Fracking and Cavern Extraction
Natural gas is often extracted by pumping water and various hydraulic fluids into deposits deep underground to lift them up by pressure alone. This is also the basic process used in hydraulic fracturing to capture oil from otherwise tapped well. Most water remains deep underground, but some amount is brought back up along with the oil or gas. Saltwater is also produced after natural gas is removed from the underground caverns used for affordable storage. These liquids are highly contaminated with both fuel and the hydraulic fluids added to increase lifting capacity. This fluid can be tricky to process and handle, so evaporation ponds play an essential role in reducing liquid volume for more affordable disposal. If a cover is used to prevent evaporation instead, the same pond structure functions as a storage space for water that is reusable for the next round of fracking or pumping.
Increasing Efficiency in Mining Ponds
Mining evaporation ponds tend to benefit from high rates of evaporation since they’re used for both harvesting and processing wastewater. Yet it’s not always obvious how to encourage faster evaporation rates when designing a pond since most regulations are focused on preventing leaks and releases. Building an efficient evaporation pond also requires the consideration of maintenance as the structure ages. These tips will help to speed evaporation rates and reduce maintenance for the pond.
- Locate the pond in the warmest possible area, whether that means selecting a specific region or just finding the hottest spot on a large property.
- Increase exposure to direct sunlight whenever possible.
- Stick with the shallowest measurements possible for the pond’s projected volume to increase surface area since water only evaporates where it meets the air.
- Install sprayer and fan systems to break up the surface of the water, which is proven to raise evaporation rates anywhere from 1% to 30%.
- Control the amount of rainwater that enters the pond with proper placement and grading.
- Choose high quality reinforced liners over clay materials to reduce maintenance costs and improve radiation effects from the sun.
