Horizontal Subsurface Constructed Wetland For Removal Of Heavy Metals From Leachate Using Phragmites Australis (a Case Of Addis Ababa Solid Waste Open Dump)

Heavy metals were present at relatively high concentrations in the landfill leachate. The disposalrnof heavy metals into the environment is of great concern due to their serious effects on foodrnchain and furthermore on animal and human health. Constructed wetlands have played arnsignificant role in treatment of domestic, agricultural and industrial wastewater containingrnheavy metals effectively. This study focused on the efficiency of horizontal subsurfacernconstructed wetland with Phragmites australis in the removal of heavy metals in landfillrnleachate. Where, it also determines the amount of heavy metals uptake by Phragmites australisrnand the amount of heavy metals retained in the soil media. In this work a laboratory-scale studyrnwas conducted on HSSF constructed wetland systems which comprises one planted and onerncontrol system. The systems operated identically at a flow rate of 22L /d and HRT 4 days forrnabout 28 days treatment period. The result shows the heavy metals composition of the leachate ofrn“reppi” open dump was significant in both season with more slightly higher in wet season. Thernexperimental study shows higher removal of heavy metals by the planted compared to unplantedrnsystem. A removal efficiency of 99.33% Fe, 93.67% Mn, 89.24% Pb, 96.14% Cu and 98.33% Znrnwere achieved in the planted system at the 28th day. While removal efficiency of 98.43% Fe,rn91.66% Mn, 85.01% Pb, 90.70% Cu and 85.19% Zn were observed in the control system at thern28th day of the treatment period. The plants uptake of Pb and Cu were also analyzed. The resultsrnshow that uptake on roots for both heavy metals were high comparing the uptake on leaves andrnstems. The ability of soil to accumulate Pb and Cu was analyzed. Soil samples were taken fromrnthe inlet, middle and outlet of control and planted system. The result shows that accumulation ofrnPb was highest on inlet part of both systems while accumulation of Cu was highest on the outletrnpart of both systems. This study concludes that HSSF constructed wetland with Phragmiternaustralis plant and red ash gravel can remove heavy metals from leachate.rnKeywords: Landfill leachate, Constructed wetland, heavy metals removal, Plant uptake, Soilrnmedia

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