Treatment of Brackish Water by Three Macrophytes in Constructed Wetlands

Series of investigations was conducted to evaluate the feasibility of using constructed wetland to remove pollutants from saline wastewater. Three emergent plants; Pistia stratiotes, Typha orientalis and Eichhornia crassipes were planted in an experimental plot and fed with saline water diluted with distilled water to simulate a brackish water concentration of 8.7 µS/cm. A pilot-scale free water surface-flow constructed wetland was set up to demonstrate the performance of sand- based constructed wetland, and removal efficiency for the selected emergent plants in treating brackish water, from diluted saline water. Treatment performances of planted units were found to be 54.5– 66% for electrical conductivity, 72.4–89.4% for Chloride, 33.3–75% for Total Hardness and 66.2–95.4% for Coliform counts. The most satisfactory plant with salt removal efficiency was Pistia stratiotes though the plant growth was limited by salt concentrations. The wetland plants were non-resistant to brackish water under the tested conditions during the 20-day retention period, with notable percentage increase in concentrations of some parameters. Salt enriched wastewater inhibited nutrients flourishing, thus reduced treatment performance. Final effluent was non-potable for human consumption, suitable for irrigation and livestock watering. Treatment system was economical and environmentally friendly, free from offensive odour and insect invasion.