Wood Leachate Remains an Issue of the Forest Industry
Wood in outdoor applications is usually pressure treated with preservatives. Since the 1970s, the majority of the woods used in outdoor residential settings have been treated with chromate copper arsenate (CCA). The most common formulation of CCA (type C) contains 47.5% as CrO3, 18.5% as CuO, and 34% as As2O5. Metal uptake rate can vary with species, density, and growth stages of aquatic plants. The heavy metals in wood leachate can be adsorbed to sediment, packing materials, and biofilms through precipitation, complexation, and ion exchange. Design considerations need to be explored for removal of both organic contaminants and heavy metals from wood leachate in constructed wetland.