Simulating phosphorus removal from a vertical-flow constructed wetland grown with C. alternifolius species

Vertical flow constructed wetland (VFCW) is a promising technique for removal of excess nutrients and certain pollutants from wastewaters. The aim of this study was to develop a STELLA (structural thinking, experiential learning laboratory with animation) model for estimating phosphorus (P) removal in an artificial VFCW (i.e., a substrate column with six zones) grown with umbrella papyrus (Cyperus alternifolius) species under a wetting-to-drying cycle. Simulations showed that rate of soluble P (SP) leaching was highest at the top zone (i.e., Zone 1) and decreased gradually with increasing zone number due to the adsorption, clogging, and plant uptake when the SP flowed through the zones. Our simulations further revealed that the best time for an optimal removal of SP from the wastewater was within the first week because the adsorption capacity of the substrate in the VFCW was highest at this time period. In general, the cumulative amounts of total P (TP) were in the following order: adsorption (53.3%) > leaching (13.5%) > uptake (0.49%). Adsorption of P was a major mechanism for P removal from the VFCW system. This study suggested that the STELLA model developed is a useful tool for estimating P removal from wastewater in VFCWs.