An evaluation of reactive filter media for treating landfill leachate

A laboratory bench-scale column study was conducted to evaluate permeable reactive filter materials as a new method for removal of heavy metals and inorganic nitrogen from landfill leachate. Mixtures of sand and peat, blast-furnace slag (BFS) and peat, and Polonite® and peat were tested by loading columns with leachate collected from a pond at Tvetaverket Landfill, Sweden. Sand, peat and Polonite® represent natural materials. BFS is a by-product from steel-works. The metal treatment efficiencies of the media were assessed and Polonite® was found to perform best, where Mn, Fe, Zn and Cu concentrations were removed by 99%, 93%, 86% and 67%, respectively. This material was also able to reduce inorganic N by 18%. The BFS showed good removal efficiency for Cu (66%), Zn (62%), Ni (19%) and Mo (16%). The sand-peat mixture did not demonstrate a promising removal capacity for any of the elements studied with the exception of Cu (25%). The removal of different elements was suggested to be a combination of several factors, i.e. precipitation, ion exchange and adsorption. Prior to full-scale application of reactive filters at a landfill site, matrix selection, filter design and operational procedures must be developed.