Willow vegetation filters for wastewater treatment and soil remediation combined with biomass production

Abstract

Vegetation filters of fast-growing trees such as willows and poplars are becoming important as an alternative to conventional treatment of wastewater and landfill leachate. Short-rotation willow coppice is a non-edible crop and has many of the requirements for a suitable vegetation filter. The filtering capacity (e.g., of nitrogen) is very high, and the crop promotes denitrification in the root zone. It has a highly selective uptake of heavy metals, especially cadmium, which enables remediation of contaminated soils. In addition, willows have a high evapotranspiration rate facilitating high loads, e.g., of polluted landfill leachate. Because of the pathogens present in municipal wastewater and sludge, special attention must be paid to storage and distribution of wastewater. In many cases vegetation filters are more cost-effective than conventional treatment methods and also facilitate recycling of valuable resources in society. Key words: bioenergy, economics, heavy metals, landfill leachates, municipal wastewater, pathogens, Salix spp., sewage sludge, wood ash