Effects of sewage sludge from wastewater treatment plants on heavy metals movement in soils, and contamination of groundwater

Heavy metals movement and accumulation in soils under the application of sewage sludge and effluent from wastewater treatment plants is a major environmental concern because transport of heavy metals through the soils may eventually lead to the groundwater contamination and accumulation in soils and crops. A silt loam soils below sludge and effluent disposal at Tehran wastewater treatment plant were studied. The vertical and horizontal distribution of sludge-borne Cd, Cr, Zn, Pb, Fe, Cu and Ni was studied in and around a four plots 2 by 6 m. Measured loadings of heavy metals to the plots from the sludge application were Fe, 284.75, Pb, 90.28, Zn, 109.5, Ni, 60.28,Cu, 27.76 Cr, 28.58 and Cd, 4.5 mg/kg. Two hundred and forty soil samples were taken from areas within the plots and up to 100 cm depth on each side of the plots. Leachate water from the plots which contaminates groundwater was collected and the concentrations of heavy metals were measured. The determined concentration of sludge-borne in leachate Cr, Ni, Zn, Fe, Pb, Cu and Cd respectively, were: 0.803, 0.785, 0.532, 0.439, 0.110, 0.180 and 0.019 mg/l. The results of this study can be used for the management of effluent and sewage application in agricultural lands and crop production. Also, the groundwater quality can be monitored and improved.

Keywords:

Contamination , Heavy Metals , Groundwater , Sewage Sludge , Wastewater