Use of Vetevera Grass (Chrysopogon zizanioides) in a Constructed Wetland to Remove Heavy Metals from Kege Wet Coffee Processing Plant, Dale Woreda, Sidama Regional State, Ethiopia

Abstract

Conventional methods for removing heavy metals from contaminated water are prohibitively expensive and, more significantly, ineffective, especially when the concentration of heavy metals is low. This paper evaluated the use of vetevera grass in a constructed wetland to remove Ca, Cd, Co, Cu, Cr, Fe, K, Mn, Na, Pb, and Zn metals from Kege Wet Coffee Processing Plant, Dale Woreda, Sidama Regional State, Ethiopia using a two vertical flows constructed wetland of 132 square meters in size with Eleven meters in length and 12 meters wide. The 11m * 3m * 1m open space between two constructed wetlands is developed. The second wetland was built, and it serves the same purpose as the previous one but discharges water into the river. The construction of the wetland is performed by digging 20 cm wide, and 30 cm apart furrows. vetiveria grasses was planted at 20 cm intervals. Heavy metals (Ca, Cd, Co, Cu, Cr, Fe, K, Mn, Na, Pb, and Zn) were measured from soil and plant samples from the inlet to the outlet sampling sites using standard procedures from two compartments (soil, and macrophytes) of constructed wetland. Findings indicated that Ca (460.0 ppm) had the highest mean concentration of heavy metals, whereas Ni (0.50 ppm) had the lowest in the soil sample. Metal absorption by vetiver grass is the highest concentration found in plant tissues grown in the following order k > Ca > Na > Mn > Fe > Zn > Cu >Ni >Cr in shoots. The order of the heavy metal contents in the roots of vetiver grass was k > Ca > Na > Mn > Fe > Zn > Cu >Ni >Cr. The plant was found to be effective at transferring Mn and Ni from the roots to the shoots based on translocation and bioconcentration, whereas it served as a potential phytostabilizer for Ca, Cu, Cr, Fe, K, Na, and Zn since the TF values are lower than 1, which show that vetiver grass prefers to accumulate heavy metals in the roots rather than the shoot and so supports its potential for phytostabilization. From the present study, it was evident that vetiver grass is an ideal candidate for wastewater treatment using constructed wetland technology.