Phosphorus removal in constructed wetlands: Can suitable alternative media be identified?”, Wetland systems, Number 2

Removal of phosphorous in subsurface and vertical flow constructed wetlands is limited by the capacity of the media to adsorb, bind or precipitate the incoming P. Several groups have carried out research on the selection of media in order to enhance the P removal capacity and therefore the life span of constructed wetland systems. The most promising results come from media rich in calcium or iron, and the suggested approaches include either the construction of the whole wetland bed with an artificial medium, or the establishment of an external P binding filter. Our studies have been focused on the evaluation of calcium rich materials that are potentially useful as P binding media. The tested materials included several types and products of calcite as well as natural sands and different types of seashells. The physical properties of the materials (texture, hydraulic conductivity, etc.) as well as their chemical characteristics have been analysed. Subsequently we have in the laboratory performed extractions, with the materials in P-spiked water (distilled and tap) at different P concentrations in order to determine P-binding equilibrium isotherms. From the most promising materials column experiments were set up simulating the conditions in subsurface flow wetlands with saturated flow. The column experiments consisted o