Nutrient removal in hybrid constructed wetlands: spatial-seasonal variation and the effect of vegetation

Abstract

Abstract Constructed wetlands (CWs) are an aesthetic and sustainable form to treat wastewater, however, their performance can be increased by improving a number of factors. The pilot-scale hybrid constructed wetland (CW) system was the combination of constructed floating treatment wetlands (CFWs) and horizontal subsurface flow constructed wetlands (HSFCWs); operated for a year and covered all seasons. The research was conducted to investigate the performance of the CW system regarding water depth, spatial, and seasonal removal of pollutants. Nine economical plants species were selected and divided into four groups to grow in CW-I to CW-IV, respectively. Removal increased along the bed and most of the total phosphorus (TP) removal occurred in the second bed, whereas total nitrogen (TN) and ammonium (NH4) removal were associated with the plant root system and biomass. Optimum removal of nutrients with respect to water depth was at 35 cm. TN and NH4 removal patterns were similar in different CWs. TN and NH4 removal were higher during summer compared to winter; only CW-IV showed the opposite trend.