Willow Woodlot Leachate Treatment

Client: 
Ecowaste Industries Limited

In partnership with the Ecowaste Landfill, SYLVIS developed an innovative soil-plant treatment system for the leachate produced at the landfill.  Landfill leachate is formed when rain water flows through a landfill and takes up organic and inorganic constituents from the landfill contents, producing a liquid that contains elevated levels of pollutants such as ammonia nitrogen and suspended solids.  An underground piping system collects the leachate, bringing it to a collection pond for treatment.

The Ecowaste soil-plant land treatment system consists of fabricated topsoil placed on four closed landfill cells and planted with coppice willows, hybrid poplars, or forage grasses.  Leachate is delivered to the soil-plant system through an irrigation system.  The vegetation takes up nutrients and water from the leachate and the fabricated soil provides additional removal of nutrients, suspended solids, and trace elements.  The primary goal of the Ecowaste soil-plant leachate treatment program is to maximize the treatment and use of the leachate, resulting in improved leachate quality and reduced discharge to surface waters. 

As a fast-growing tree species capable of rapid nutrient and water uptake, coppicing willows are a vital component of the landfill leachate treatment system.  Hybrid willows are planted in high density plantations and are harvested every three to five years.  The plantations may last up to 30 years resulting in nine to ten harvests from a single planting.  SYLVIS researched the ideal soil formulation and selected the variety of coppicing willows with the highest performance potential for the site conditions.  SYLVIS carried out the plantation establishment including soil fabrication, soil placement, and planting of the willows, and continues to manage the irrigation, maintenance and harvest of the willow biomass in coordination with the entire leachate treatment system at the Ecowaste Landfill.

The willow woodlot provides effective leachate treatment and secondary benefits such as improved aesthetics of the landfill and production of valuable biomass.  Since the start of its operation, the willow woodlot has consistently reduced the levels of contaminants in the leachate to meet the discharge parameters outlined in the Ecowaste Landfill operational certificate.  The harvested biomass from the willow woodlot has been successfully used by the Ecowaste Landfill at their composting facility.