Solubilization of heavy metals from a river sediment by an olive oil mill effluent at different pH values

Abstract

The effect of solutions of wastewater from olive mill, called 'alpechin', on the solubilization of Ni, Cd, Zn, Cu, Mn, Pb and Fe present in a sediment from Agrio river (Seville, Spain) at pH 3, 4 and 5 is studied. Metal solubilized by alpechin solutions is compared with data from different fractions of metal speciation of the sediment. The data shows that the dominant effect is pH for all metals with the exception of Fe and Mn. Within a given pH, it is shown that the presence of alpechin solutions causes mobilisation of most metals studied at pH 5 except Cd and Zn and this effect is progressively less marked as pH decreases, so that at pH 4 mobilisation is detected for Ni, Cu, Mn and Pb, and at pH 3 only is noticeable for Ni and Mn. The joint effect of pH and of the presence of alpechin is the release of amounts of metals which are comparable to those metal fractions attributed to exchangeable and bound to carbonates.