Residual Wastewater Treatment by an Aquatic Plant System in Tropical Area: Assessment of Arundo Donax and Pennisetum Purpureum Schumach

This study examines the potential of two local reed species (Arundo donax and Pennisetum purpureum Schumach) from Uíge province, Angola, to purify wastewater from the Kimpa Vita University Campus, under a vertical flow regime, and in a tropical climate. The assessment performance of these macrophytes is based on an experimental system with three plastic basins, with a capacity of 84 L each, containing a 0.25 m-thick layer of gravel and topped with a layer of sand of 0.1 m. The first basin is planted with Arundo donax, the second with Pennisetum p. Schumach, and the last is without vegetation cover. The obtained results show that the effluent treated by the planted filters has a better mineralization, with a satisfactory Chemical Demand for Oxygen (COD), unlike the unplanted filter. Indeed, the action of the roots and rhizomes allows a significant elimination of nutrients, although the average abatement in Biochemical Demand for Oxygen for five days (BOD5 ) of the whole system is low. In addition, the microbiological elimination of faecal coliforms is good on average and the effluents purified by these filters are clear and odorless. The planted filter of Arundo donax allows better elimination of Escherichia coli (E. coli) and enterococci compared to that of Pennisetum p. Schumach.