Leachate. What is it?
Solid waste that cannot be recycled or reused is often sent to an approved landfill site. Landfill sites are large pits into which the waste is deposited and then covered with soil. When rain falls on the landfill area, water can seep through the buried waste and pick up contaminates. This is referred to as leachate. Depending on the type of waste in the landfill, leachate may contain high concentrations of contaminants and can range in colour from clear to dark brown.
Why does it matter?
Leachate may flow towards surface water, such as lakes and rivers, or it may flow into groundwater several metres below the land’s surface. If the leachate contains contaminates, it can pollute the surface or groundwater over a large area. Groundwater pollution can be very serious, especially if the groundwater is used as a fresh-water supply for households.
How is it controlled?Leachate impacts are minimized in several ways:
- Limiting the disposal of hazardous materials in the landfill site;
- Collecting and monitoring the leachate and treating it, if necessary, before discharging it;
- Installing liners or clay-like materials on the bottom of the landfill to prevent seepage of the leachate to the groundwater; and;
- Using a cover material, such as clay, with vegetation to minimize water penetration into the site.
The Thunder Bay mill has a closed landfill site that has a state of the art groundwater collection system. All groundwater passing through the old landfill site is collected and pumped to a sewage treatment plant.