Soil-Plant Phytoremediation System

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Ecowaste Industries Limited

The Ecowaste Landfill located in Richmond, British Columbia accepts non-putrescible waste, primarily from construction and demolition activities.  Production of landfill leachate is an ongoing environmental challenge at the landfill.  Leachate is formed when water moves into and through the buried waste taking up organic and inorganic constituents.  The resulting liquid contains elevated levels of contaminants such as ammonia nitrogen and suspended solids, and must be treated before discharge.  At Ecowaste, a series of berms and engineered piping system direct the leachate to a collection pond for treatment.

Ecowaste retained SYLVIS to develop and implement cost-effective management of landfill leachate in conjunction with landfill closure operations.  A land treatment option consisting of fabricated soil planted with either hybrid poplars, coppicing willows or forage grasses was identified as a suitable option to remove contaminants and reduce the overall leachate volume.  SYLVIS provided turn-key consulting and contractor operations including design, management, soil fabrication, plantation establishment, silviculture management and performance monitoring.  Soil was fabricated using a specific ratio of biosolids, wood shavings and dredged sand in order to provide the “ecosystem infrastructure” for the establishment of vegetation and promotion of leachate treatment.  The soil-plant system was established on the closed portions of the landfill which allows greater control over the system design, characteristics and abilities, while also conserving valuable real estate space.  Vegetation was selected for plants with high nutrient and water demand.  Additional consideration was given to the ability to harvest the vegetation.  Harvesting of the trees and grasses effectively exports the captured leachate nutrients from the landfill site and provides a source of value added products which can be used for power generation or composting.

The combination of fabricated soil and vegetation provides an effective avenue for leachate treatment, capable of year-round nutrient reduction through uptake and biotransformation processes within the soil.  The soil-plant system has exceeded expectation in terms of performance, with the ability to successfully treat seasonally fluctuating volumes of leachate produced at the Ecowaste Landfill.