Using constructed wetlands for the treatment of woodwaste leachate

Rainfall percolating through wood chip piles, hog fuel, and log storage areas will leach naturally occurring chemicals from the wood. This leachate is often characterised by high carbon content, strong color, and high concentrations of tannins and lignins, resin acids and phenolics. This produces a leachate very toxic to aquatic life, and has serious implications from an environmental discharge viewpoint. It can lead to regulatory problems for facilities operators. A wetland-based biological treatment process is being developed as a practical treatment alternative. Its objectives are to develop a low-cost, passive treatment process that is capable of reducing the leachate's toxicity. Laboratory bench-scale experiments have achieved a greater than 50-fold reduction In toxicity and the process appears to be very amenable to field-scale application. A pilot-scale testing facility, consisting of six experimental wetland cells, was constructed outside of Vancouver, British Columbia, Canada. Successful trials will produce a treatment system that requires minimal operational attention, infrastructure, chemical addition, or materials and byproducts handling. Possible applications include treating stormwater runoff from staging areas and log yards, collection and treatment of leachate from chip and hog fuel piles, and detoxification of non-point source contamination from parking lots and other wood processing work areas.