Performances of a Yard-Scale Surface Flow Wetland Vegetated with Echinochloa Crus-Pavonis in the Removal of Nutrients and Faecal Bacteria from Domestic Wastewater

Abstract

Several macrophytes are being tested in experimental wetlands systems in Cameroon, for the treatment of domestic wastewater. The aim of the present research was to assess the performances of a yard scale surface flow wetland vegetated with Echinochloa crus-pavonis, in the removal of nutrients and faecal bacteria from primarily treated effluent. A wetland vegetated with the macrophyte and a non-vegetated wetland (control) were continuously fed with primarily treated domestic wastewater at organic loading rates varying from 20.74 to 27.15 g BOD/m²/day in dry season and the rainy season for two consecutive years. Physicochemical and microbiological characteristics of water were monitored at the entries and exits of the wetlands alongside the growth attributes of the young plants during each season. Plant densities in the bed increased with time during each season of the experiment, and not significantly lowered during the following season after harvest. Percentage removal ranges of 89-95 % and 75-93 % were observed for faecal bacteria during the dry and the rainy seasons respectively in the vegetated beds, as compared to ranges of 25-71 % and 24-73 % recorded in the control bed. The same trend was observed for nitrates and orthophosphates with removal rates of up to 62 % and 82 % respectively as compared to 40 % and 47 % recorded in the control. The vegetated bed was significantly more efficient than the control in the reduction of several parameters, but this varied with seasons.