Processes comparison for nickel and chrome removal from urban landfill leachate

This study aims to examine the feasibility of chemical, physical and biological processes on municipal landfills leachates, to mainly evaluate Nickel (Ni) and Chrome (Cr) removal. Flocculation/coagulation methods were investigated on laboratory scale, by dosing ferric chloride (FeCl3) and aluminium polychloride to three leachates, at a natural pH of 8. The oxidation treatment with sodium permanganate (NaMnO4), applied on the leachate with higher metals content, defined an increment of Ni (from 9 to 50%) and Cr (from 31 to 80%) removals, compared with the previous chemical treatments. Further, the metals biosorption capacity on the biomass flocs was investigated in a pilot scale membrane bioreactor, previously tested on laboratory scale. The different percentages of added leachate showed efficiencies up to 93% for Cr and 58% for Ni, defining the different removal roles of the adsorption and of the membrane layer effect.