Effect of cleanup of spiked sludge on corn growth biosorption and metal leaching

Abstract

A chemical leaching process was used for the cleanup of two municipal biosolids (MOS and BES) spiked with Cd, Cu, Zn or their mixture prior to agricultural use. Non-cleaned, cleaned and washed biosolids were compared as soil amendments for corn cultivation in greenhouse. Corn growth, biosorption and metal leaching were measured. Results showed that biosolid amendments tend to produce more aerial biomass. Cleanup and washing of BES biosolid significantly increased total biomass of roots and stalks, respectively. Regarding biosorption of metals, Cd accumulated in roots (0.06–1.13 mg kg−1) and leaves (0.06–0.63 mg kg−1), but not in seeds nor in stalks. Larger amounts of Cu were detected in roots (10.7–18.2 mg kg−1), stalks (1.29–3.78 mg kg−1) and leaves (6.77–20.2 mg kg−1). However, Zn was more accumulated in roots (17.9–74.9 mg kg−1), stalks (6.15–17.1 mg kg−1) and leaves (47.9–90.1 mg kg−1). Whereas Cd and Cu decreased in the order roots > leaves > stalks, Zn decreased from leaves > roots > stalks. Cleanup and washing of MOS and BES biosolids significantly lowered biosorption of Cd (up to 84%), Cu (up to 38%), Zn (up to 63%), and other metals. Concentrations in leachate draining into outlet water varied over time, but on average were moderately low. Significant amounts of metal leached from MOS biosolid. The effects of cleanup and washing of both biosolids on biosorption and leaching depended on the initial metallic charge and the biosolid type.