The efficacy of Vetiveria zizanioides in horizontal subsurface flow constructed wetland for treating textile wastewater

Abstract

Textile wastewater discharged into rivers often triggers a decrease in water quality and causes harm to its aquatic ecosystem. Textile wastewater, which may contain nutrients, organic compounds, and heavy metals, can be managed using a constructed wetland system. Vetiver grass is known for its ability in treating polluted waters, though the information related to its potential in controlling textile wastewater pollution in riparian areas is still limited. This study aimed to determine the efficacy of a pilot scale constructed wetland system using vetiver grass (Vetiveria zizanioides) for the removal of several pollutants in a riparian area polluted by textile wastewater. The wastewater flowed horizontally through the sub-surface layer of the system with a hydraulic retention time of two days. The wastewater was diluted to 20%. Three systems were made by varying the porous size of planting media using coarse gravel, fine gravel, and sand. The systems were then run for three months. Of the three constructed wetland systems, the highest removal efficiency (RE) was achieved for the NH4+ parameter with an average removal efficiency higher than 60%. The highest nutrient RE was achieved by the system with sand in the growing media, with NH4+ RE of more than 80%. RE values were fluctuating until the end of the experiment, which might occur because the system was not yet stable. It may take longer operation time to get a better system performance in removing the pollutants contained in the textile industry waste.