Removal of phosphorus via water weed cutting of emergent vegetation in constructed wetlands for wastewater treatment

Abstract

The amount of phosphorus, which could be removed from wastewater via harvesting is given by phosphorus standing stocks and the harvesting schedule. Available data from 28 constructed wetlands around the world indicate standing stock in the range of 0.4 to 10.5 g P m-2, 0.6 - 9.8 g P m-2 and 0.2 to 6.5 g P m-2 for Phalaris arundinacea, Phragmites australis and Typha spp., i.e. the most commonly used plants in constructed wetlands. The inflow loading values vary widely among systems; for the systems designed for the secondary treatment of sewage inflow P loadings usually range between 100 and 200 g P m-2 yr-1 but values up to 800 g P m-2 yr-1 have been reported. These figures clearly indicate that the amount of P removed via harvesting is usually low. However, for tertiary treatment systems with inflow < 20 g P m-2 yr-1 this removal route could be significant.