The effect of Phragmites australis on removal of copper, lead, zinc and cadmium in constructed wetland

This study investigated the effect of Phragmites australis in constructed wetlands for removing copper, lead, zinc and cadmium and different concentrations of COD. In order to study various parameters such as pH, initial concentrations of COD (120, 500 and 1000 mg / l) and initial concentrations of copper, lead, zinc and cadmium (2, 10 and 30 mg / l). PVC pipes with an inner diameter of 16 cm and a height of 70 cm were made as columns to simulate the performance of constructed wetlands. For evaluating these parameters, Effluent wastewater samples were calculated according to the hydraulic retention time (3 days) from the outlet of the column. The results showed that the biomass of the roots of wetland plants had a positive effect on the removal efficiency. In addition, the results of pH evaluation showed that the amount of pH was decreased with increasing of zinc, cadmium, copper and lead′s concentrations. Moreover, according to the results, the maximum COD removal efficiency (17.25%) was occurred in 500 mg/l. The results of pollutant removal efficiency showed that with increasing the concentration of pollutants from 2 mg/l to 10 mg/l, the removal efficiency was increased, then with increase of initial concentrations of heavy metals to 30 mg/l it was decreased. The highest removal efficiencies of copper, lead, zinc and cadmium ions in 90 minutes were 63.84%, 60.77%, 59.14% and 57.71%, respectively. According to the results, the presence of Phragmites australis and use of constructed wetland systems with sandy bed showed a positive effect on the removal efficiency of copper, lead, zinc and cadmium, but was not effective on COD removal efficiency.