“…The CTWs tested were a horizontal subsurface flow system equipped with coarse gravel, medium-sized gravel, and sand that functioned as adsorbent/filtration as well as Vetiveria zizanioides and Heliconia psittacorum; as well as natural adsorbents such as bentonite and zeolite with a horizontal flow system. There have been a few studies on CTW systems that use Heliconia psittacorum for removing heavy metals [1], aquaculture effluent in a number of free surface flow CTW systems [2], and municipal waste as a secondary treatment in a hybrid CTW system [3,4,5,6]. Although mostly studied in a secondary treatment for greywater and municipal wastewater, a horizontal subsurface flow constructed wetland (HFCW) system has been found to have moderate to high removal efficiency (RE) of TSS, COD, TN, TP, ammonia, and nitrate.…”