Phytoremediation as a Prospective Method for Rehabilitation of Areas Contaminated by Long-Term Sewage Sludge Storage: The Greek Experience

Abstract

In this work the suitability of several plant species for phytoremediation under natural and artificially installed conditions was studied. Brassica napus, Medicago sativa, Zea mays, Triticum aestivum, and Hordeum vulgare were grown in pots with sewage sludge from Sindos Main WWTP in Thessaloniki and from Sindos Industrial WWTP in Thessaloniki, Greece.

The first series of experiments included comparing measurements of various parameters for the above mentioned plants and the sludge to those for control samples (the same plants growing in compost). It was shown that shoot growth was less reduced in T. aestivum and H. vulgare than in the other plant species studied. B. napus had lower germination tax, followed by M. sativa with the lowest germination tax. Generally B. napus, giving less biomass production than Z. mays and T. aestivum, is characterised by a higher ability to accumulate heavy metals like Cd, Cu, Ni, Pb, Zn, Cr, As and Hg.

The second series of experiments included comparing measurements of various parameters of B. napus grown in sludge and treated each 7 days with metal solutions of Ni, Zn and Pb containing 10^-2mg/l, 10^-4mg/l, 10^-6mg/l of each metal, to those for control plants treated with double distilled water. Results showed that shoot growth of B. napus were increased at treatments with lower concentrations of metals (10^-6 mg/l) and control (treatment with d-distilled water). At the same time uptake of metal ions was increased with the concentration of the solution, i.e. at higher concentrations (10^-2 mg/l). It is truly for Pb and Zn, transfer coefficient TC of which (indicates a plant’s potential to concentrate a metal) was quite high 15 % and 7 % correspondingly. It was noticed that B. napus has high ability to accumulate Cr, from the other hand it did not accumulate Ni (at present case).