Phitoremediation of Kipevu waste water using vetiver grass (Chrysopogon zizanioides)

Abstract

Treatment of wastewater worldwide has mainly been done using physical, chemical and biological wastewater treatment systems such as activated sludge and biological nutrient removal technologies (Bedewi, 2010). Mombasa City produces large amounts of effluent water that is collected and primarily treated and discharged to the Indian Ocean. Too many pollutants in water bodies pose threat to the aquatic species. The main aim of the study is to come up with an economically and environmentally friendly technology that will enhance the treatment of Kipevu waste water treatment plant. Field experiments were conducted in plastic containers of five litres which were set-up simultaneously with planted vetiver hydroponically and with no vetiver as a control, which was replicated thrice in four containers. Wastewater was characterized for physicochemical parameters before and after treatment with vetiver grass. The parameters studied were; effects of vetiver on reduction of pollutants with time, effect of biomass (number of Vetiver plants) on treatment efficiency. Wastewater had high levels of Chemical Oxygen Demand (1440mg/L), Biological Oxygen Demand (75 mg/L) nitrates (775 mg/L), phosphates (25mg/L) and IDS (1 432mg/L) were beyond the Maximum contaminable levels. There was a drastic increase in the pollutants uptake with time. The levels of nitrates, phosphates, chemical oxygen demand, biological oxygen demand and total dissolved oxygen reduced by 89.76%, 85.6%, 84.51%, 69.33% and 16.76% respectively in 28 days. In 28 days, chemical oxygen demand reduced by 91.08%, 92.17 % and 94.92% while nitrates decreased by 85.59%, 87.5% and 92.35% % for 4 plants, 8 plants and 12 plants per 5 litres of wastewater respectively. The potential of vetiver grass after four weeks hydroponic treatment was found to be efficient in the reduction of pH, nitrates, phosphates, total nitrogen, total phosphorous, total dissolved solids, chemical oxygen demand and biological oxygen demand.