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Phytocap Technology Installation to Reduce Leachate Generation

Pacific Environment undertook a feasibility study for a Council to find an alternative capping system to reduce leachate generation. This project included a review of the leachate, groundwater and surface water processes for the Killaloe landfill.

Large amounts of rainfall prove difficult

Killaloe landfill is located in Tropical North Queensland and experiences a high amount of rainfall, with a mean annual rainfall of approximately 2 m a year. Leachate is primarily generated by rainfall falling on the site and infiltrating though the current cap to the waste cells below. The conceptual groundwater model indicates that regional groundwater is not contributing to leachate generation at the site, meaning rainfall is the primary method for leachate generation. The water balance is the term used to describe the balance of inputs (rainfall) into the system versus the outputs (evaporation and evapotranspiration). Currently it is difficult to maintain low water levels in the landfill and the bundled irrigation areas, particularly in times of very wet weather.

phytocap technology installation benefits

Our Phytocap Technology Provides Leading Solution

For this feasibility study, a composite phytocap was considered to be a suitable option to reduce the leachate generation. This alternative landfill cap would reduce rainfall infiltration, by redirecting clean runoff from the site, as well as induce evapotranspiration from water stored in the phytocap soil. In this case due to the high rainfall at the site, it was proposed to place the composite phytocap soil on top of a low permeability clay cover. This would limit any excess leakage through the phytocap.

A drip irrigation system, using leachate, applied to the phytocap and Vetiver planting areas on the side slopes would be effective in reducing leachate volumes by evapotranspiration, which has a greater loss rate than that of pan evaporation only at these latitudes. As a result, the evaporation ponds could be slowly decommissioned as the phytocap and Vetiver system would begin to take the bulk of the leachate volume for removal.