Performance evaluation of phosphorus removal by apatite in constructed wetlands treating domestic wastewater: column and pilot experiments

In constructed wetlands (CWs) treating domestic wastewater, good treatment performance is obtained on mains parameters except phosphorus (P) which can cause eutrophication problems. In order to improve P removal from wastewater with a low specific filter surface per person equivalent (pe), different materials have been tested: man-made and natural materials, industrial by-products, and a mixture of these materials. The P removal by natural apatite has been studied by only a limited amount of work. Apatite materials appear to possess high and long-term removal capacity, thus a better knowledge is needed to determine the quality of apatite to be used and the P removal evolution with time and water quality. In this work the P removal rates were studied in two different scales (lab-experiments and pilot units) on different apatite qualities. Removal rate in the pilot units was smaller than the one found in lab-scale columns and the results suggested that a security coefficient might be applied while designing the apatite filter.