Leachate treatment by floating plants in constructed wetland

Abstract

Leachate generation was one of the major concerns of a landfill. Leachate contained high levels of organic and inorganic matters. As the landfill leachate was highly contaminated, leachate could not be discharged directly into the surface water bodies. Therefore, leachate treatment was essential before it was discharged into receiving water. Constructed wetland emerged as one of the potential treatment alternative that employed floating plants to remove pollutants form leachate. In this research, a constructed wetland was developed by using Eichhornia crassipes to treat landfill leachate. Different leachate concentration (100%, 50%, 25%) was studied in the constructed wetland to compare the treatment efficiency in terms of pollutants removal in leachate and the heavy metal uptake by Eicchornia crassipes. The treated leachate was analyzed for nutrient and heavy metal removal. The growth of Eichhornia crassipes was observed and the plants were digested at the end of experiment to study the heavy metal uptake by plant. The results showed that the wetland with 100% leachate concentration was the most efficient in removing BOD (74.04%) and Fe (100%) while wetland of 50% leachate concentration was the most efficient in removing NO3 --N (64.51%) and Mn (53.13%) compared to 25% wetland. The higher the concentration of leachate, the more the plants wilt and this resulted in less accumulation of heavy metal in plants. Eichhornia crassipes had a higher capacity to accumulate Fe and Mn in the roots than in the leaves. At the end of experiments, the pH of the leachate decreased in all wetland regardless of the leachate concentration. pH decrease was due to heavy metal uptake by plants and nitrification process by microorganisms. As a conclusion, this study showed that wetland was efficient in removing BOD and NO3 --N in high leachate concentration. The wetland also posed a great role in removing Fe and Mn through plant uptake.