Abstract:
Many of the natural systems have been polluted by direct discharge of waste water to the water bodies that causes environmental and health hazards. The surface water resource mainly the tank water gets polluted due to waste water discharge to the tanks without proper treatment in Vavuniya district which consists of many tanks polluted due to the direct discharge of storm and runoff water. Natural wetland system is believed to be a most preferable secondary treatment system to treat the waste water before discharge into the water bodies. The natural grasses and sedge species are the basis of phytoremediation technique to remove the pollutants. Objective of this study was to assess the pollution reduction ability of these grass spp. The waste water was collected in between the grid and oxidation pond in Vavuniya tank in two weeks interval and passed it through the constructed wetland system with three different spp. of grasses such as Eleucine indica (Goose grass), Dactyloctenium aegyptium (Crowfoot grass) and a sedge namely Cyperus iria (umbrella sedge) and the control without any grass were operated continuously by inlet valve from tank filled with waste water. The physicochemical
parameters such as pH, Dissolved Oxygen (DO), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), and Total Solids (TS), concentration of phosphate and nitrate of water were measured for the inlet wastewater and the outlet water after passing through the wetland system in two weeks interval. Results of the physicochemical parameters showed that the grass spp. and the sedge reduces the pH, COD, BOD, TS and the concentrations of phosphate and nitrate and increases the DO significantly.
Further the results also revealed that among the three species tested, the sedge Cyperus iria is more effective in reducing the pollution level of waste water.
