Wastewater treatment in constructed wetlands (CWs) offers a sustainable, eco-friendly and economical technology than others conventional wastewater treatment system [1]. They provide physical, chemical and biological processes of removal of pollutants (Adeniran et al.). It includes processes of sedimentation, hydrolysis, adsorption, microbial degradation and direct uptake by plants. Horizontal subsurface flow CWs (HSSFCWs) are increasingly popular, in particular due to their reduced surface requirements. They are also revealed to provide different redox conditions in which pollutants get into contact with a network of aerobic, anoxic and anaerobic zones during their passage through the HSSFCWs [1]. Furthermore, they are reported to offer a high purification efficiency of organic matter including numerous pesticides [2-4]. However, studies are limited in assessing the feasibility of using HSSFCWs for removal of most of the priority pollutants given by the European Water Framework Directive at field conditions.