Soil-Plant Phytoremediation System
The Ecowaste Landfill, located in Richmond, British Columbia, accepts waste primarily from construction and demolition activities. Production of landfill leachate is an ongoing environmental challenge at the landfill. Leachate is formed when water percolates through the buried waste, taking up organic and inorganic constituents. The resulting liquid contains elevated levels of ammonia nitrogen and suspended solids that must be reduced to environmentally conducive levels before discharging to off-site surface waters. At Ecowaste, a series of berms and an underground piping system direct the raw 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 areas of hybrid poplars, coppicing willows, and forage grasses was established, managed, and continually optimized by SYLVIS over a span of 15 years. 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 adequate nutrients and soil tilth for the establishment of vegetation and promotion of leachate treatment. The soil-plant phytoremediation system was established on four closed cells of the landfill, conserving valuable space for landfill operations and allowing beneficial end-use of the leachate to be utilized on site. Plant species implemented within the soil-plant phytoremediation system were chosen for their high nutrient demand, water demand, and harvestability. The soil-plant phytoremediation system utilized forage grasses for leachate treatment on all treatment lots, due to the ease of biomass removal via haying events and the added benefit of repurposing hay bales for on-site erosion control. Harvesting the grasses effectively exported the captured leachate nutrients from the lot and provided a value-added product.
The combination of fabricated soil and vegetation provided an effective avenue for leachate treatment, capable of year-round nutrient reduction through uptake and biotransformation processes within the soil. The soil-plant phytoremediation system exceeded expectation in terms of performance, with the ability to successfully treat seasonally fluctuating volumes of leachate produced at the Ecowaste Landfill.