Horizontal Subsurface Constructed Wetland for Removal of Heavy Metals from Leachate Using Phragmites Australis (A Case of Addis Ababa Solid Waste Open Dump)
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Date
2013-04
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Addis Ababa University
Abstract
Heavy metals were present at relatively high concentrations in the landfill leachate. The disposal
of heavy metals into the environment is of great concern due to their serious effects on food
chain and furthermore on animal and human health. Constructed wetlands have played a
significant role in treatment of domestic, agricultural and industrial wastewater containing
heavy metals effectively. This study focused on the efficiency of horizontal subsurface
constructed wetland with Phragmites australis in the removal of heavy metals in landfill
leachate. Where, it also determines the amount of heavy metals uptake by Phragmites australis
and the amount of heavy metals retained in the soil media. In this work a laboratory-scale study
was conducted on HSSF constructed wetland systems which comprises one planted and one
control system. The systems operated identically at a flow rate of 22L /d and HRT 4 days for
about 28 days treatment period. The result shows the heavy metals composition of the leachate of
“reppi” open dump was significant in both season with more slightly higher in wet season. The
experimental study shows higher removal of heavy metals by the planted compared to unplanted
system. A removal efficiency of 99.33% Fe, 93.67% Mn, 89.24% Pb, 96.14% Cu and 98.33% Zn
were achieved in the planted system at the 28th day. While removal efficiency of 98.43% Fe,
91.66% Mn, 85.01% Pb, 90.70% Cu and 85.19% Zn were observed in the control system at the
28th day of the treatment period. The plants uptake of Pb and Cu were also analyzed. The results
show that uptake on roots for both heavy metals were high comparing the uptake on leaves and
stems. The ability of soil to accumulate Pb and Cu was analyzed. Soil samples were taken from
the inlet, middle and outlet of control and planted system. The result shows that accumulation of
Pb was highest on inlet part of both systems while accumulation of Cu was highest on the outlet
part of both systems. This study concludes that HSSF constructed wetland with Phragmite
australis plant and red ash gravel can remove heavy metals from leachate.
Keywords: Landfill leachate, Constructed wetland, heavy metals removal, Plant uptake, Soil
media
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Keywords
Landfill Leachate, Constructed Wetland, Heavy Metals Removal, Plant Uptake, Soil Media