Modeling Heavy Metals (Cr, Ni, Pb) Transport In Soil Under Sewage Sludge Application

The purpose of this study is to assess the possible contamination of the groundwater by heavy metals derived from sewage sludge through a plot study. For this purpose, two experimental plots, each size 2 by 10 m at Wastewater Treatment Plant-Shoush was prepared. A pvc drainage pipe was installed in one meter depth of each plot to collect the leached water. The first plot was irrigated with pipe water as control plot. The second one with sewage sludge from Shoush wastewater treatment Plant where is located in the south of Tehran. Soil samples were taken from the topsoil to 100 cm depth, each sample for every 10 cm depth from each plot. Cr, Ni and Pb concentration was measured as a function of depth after 150 days. Hydrus-1D was calibrated for heavy metals transport in the site. Modeling and experimental results were nearly the same. Simulation results for plot 2 indicated small risk of groundwater contamination. However high concentration of heavy metals near the soil surface raises a concern about leaching as macro pore and preferential flow. Simulation results for plot 2 indicates that in Hydrus -1D adsorption parameters were estimated in order to allow a deeper transport of heavy metals which had actually occurred duo to macro pore flow.