Chromium removal efficiency by Colocasia esculenta (L.) Schott in constructed wetlands for tannery post-treatment wastewater

Abstract

The purposes of this study were to determine and compare the chromium removal efficiency of two types of Colocasia esculenta (L.) Schott which was green and violet stems in constructed wetlands for tannery post-treatment wastewater at three wastewater level (0.15, 0.25 and 0.35 m), to compare chromium accumulation in between phases of system and in various parts of emergent plant, i.e lamina, petiole, corm and root. In addition, to investigate the plant growth rate of both plants in condition as mentioned. Twelve FWS constructed wetland units were built for this study. Nine of them were used for study about the chromium removal efficiency and three units for studying the plant growth rate. From the results, the average chromium removal efficiencies of green and violet C. esculenta in every wastewater level were 67.01% and 59.95%, respectively. Wastewater level had no significantly effect on all system efficiencies, resulted from plant dead during experimental run time. It perhaps resulted from phenomenon as called “salt stress effect". For chromium accumulation in wetland systems, soil bed was the most accumulation. Moreover, amount of chromium accumulated in root was more than other parts in every wastewater level units of both plants (average at 0.2533 mg/g (dry weight) for green C. esculenta and 0.2478 mg/g (dry weight) for violet C. esculenta). In conclusion, these plants were not suitable for treatment tannery wastewater because they could not tolerate in high salt conditions. However, it was found that they were able to assimilate heavy metal that was chromium at very well. So, they tended to be used for removing other toxic substances especially, heavy metals in the future study.