Heavy metal removal from sewage sludge by plants

In this study, the phytoextraction of heavy metals from sewage sludge by native plants and the effects of sulfur, agricultural gypsum and EDTA chemicals to this process have been determined. Conyza canadensis, Conium maculatum (Poison hemlock), Datura stramonium, Brassica juncea (India mustard), Pelargonium hortorum (Geranium) ve Brassica oleraceae var. oleraceae (Black cabbage) were growing on sewage sludge for the removal of Pb, Zn, Cu, Cr, Ni and Cd. Among the plants tested, the concentration of Cu, Cr and Pb in Brassica juncea was significantly higher than the others such as Cu: 109.92 mg kg-1 root-48.82 mg kg-1 shoot, Cr: 169.58 mg kg-1 root-64.69 mg kg-1 shoot and Pb: 42.27 mg kg-1 root-81.5 mg kg-1 shoots. While the maximum root Zn concentration was obtained at Brassica juncea (680.99 mg kg-1), highest shoot level was determined at Datura stramonium (259.45 mg kg-1). Conyza canadensis was the most conspicuous plant at the Cd removal, such as 2.81 mg kg-1 and 3.61 mg kg-1 Cd obtained at root and shoot. The highest Ni concentrations were obtained at Datura stramonium, concentrations in order of 57.29 mg kg-1 and 18.42 mg kg-1 for root and shoot. Whilst Brassica juncea, Datura stramonium ve Conyza canadensis were obtained as the most evident plants at heavy metal removal, Conium maculatum, Brassica oleraceae var. oleraceae and Pelargonium hortorum were not appear to accumulate tested metals. Except Cd, EDTA was the most effective amendment at the phytoextraction process for all metals. Also the most pronounced effect was obtained at sulfur for Cd removal. Tested plants were removed heavy metals from sewage sludge by 65% and the residual of 35% was not removed by plants for the lower bioavailability. For all the plants, maximum biological accumulation factors (>1) were observed for Cu, Cd and Pb whereas factors were obtained lower for Zn, Ni and Cr (<1). Translocation factors were determined >1 only for Cd and Pb metals.