Metal retention from landfill leachate by glacial clays: laboratory experiments

This paper is part of the special publication No.157, Chemical containment of waste in the geosphere (eds:R.Metcalfe and C.A. Rochelle). Two sets of laboratory experiments were carried out to investigate the role of clay liners on the retention of metals present in landfill leachate. In the first experiment leachate was passed through clay filled columns and comparisons made of the metal content in treatment columns (leachate) with that in the control columns (de-ionized water). The metals Na, K, Mg, Ca, Al and Fe show elevated concentrations when compared with the control columns. In addition, a black sludge was observed on the upper surface of the treatment columns. On analysis this sludge was found to be Fe-rich when compared with the surrounding leachate/clay matrix. In the second experiment a simple tank system was used to investigate sludge formation at the leachate:clay liner interface. The observed sludge was found to have elevated metal concentrations, with a corresponding decrease in metal levels in leachate samples, compared with analysis before the experiment. From these observations it was concluded that the sludge may be acting as a sink for key metal contaminants from leachate.