EnvironmentAsia (Jun 2014)
Improvement of Groundwater Quality Using Constructed Wetland for Agricultural Irrigation
Abstract
This research was designed to evaluate the performance of Constructed Wetlands (CW) for groundwater quality improvement. In the first phase of this study, performance of CW planted with cattails for Manganese (Mn) and Iron (Fe) reduction was evaluated at 12, 24 and 48 hours of Hydraulic Retention Time (HRT). Average efficiencies of all tested CW systems were higher than 90 and 75% for Mn and Fe concentration reduction. Subsequently, the efficiency of CW operated at 12 hours of HRT was investigated at different plant harvest intervals. In the second phase of study, Mn and Fe removal efficiencies were 75-100 and 48-99%, respectively. Both Mn and Fe removal efficiencies for the CW system were not different between 4, 6 and 8 weeks of harvest intervals. However, the efficiency obviously increased after the first plant harvest. Average Mn and Fe removal rates of the CWs operated at the tested harvest intervals were 0.068 to 0.092 and 0.383 to 0.432 g/m2/d, respectively. Fe removal rate was not significantly different under the various test conditions. However the highest Mn removal rate was obtained in CWs operated with a harvest interval of 4 weeks. Mn accumulation rates in cattail shoots and roots were 0.04-8.25 and 0.83-23.14 mg/m2/d, respectively. Fe accumulation rates in those were 0.04-164.27 and 249.62-1,701.54 mg/m2/d, respectively. Obviously, cattail underground tissues accumulated both Mn and Fe at higher concentrations than those of the above ground tissue. These results show that CW can improve the quality of groundwater before agricultural irrigation.
