Evaluation of coagulation (FeCl3) and anion exchange (MIEX) for stabilized landfill leachate treatment and high-pressure membrane pretreatment

Abstract

Laboratory-scale experiments were conducted to assess the effectiveness of coagulation (ferric chloride – FeCl3) and magnetic ion exchange (MIEX) as a pretreatment option for treating stabilized landfill leachate using reverse osmosis (RO) and nanofiltration (NF) membranes. Leachate from three different landfills was collected and characterized as stabilized leachate with a ratio of biochemical oxygen demand to chemical oxygen demand in the range of 0.02–0.11. Batch jar-tests were conducted to determine the effectiveness of FeCl3 and MIEX. A maximum reduction of 71% and 34% dissolved organic carbon (DOC) and 94% and 48% UV-254 absorbing organic matter (OM) was observed using FeCl3 and MIEX, respectively. Effective doses of FeCl3 (22mmolL−1) and MIEX (5mLL−1) were selected for leachate pretreatment before membrane operation. Batch RO and NF membrane experiments were conducted with raw and pretreated leachates to study the change in permeate flux for each type of membrane and leachate. Even though the pretreated leachate contained over 45% less UV-254 absorbing OM than raw leachate, leachate pretreatment did not increase the permeate flux as compared to raw leachate during RO and NF membrane treatment. The potential cause of the decrease in permeate flux in pretreated leachate as compared to raw leachate was hypothesized as the change in characteristics of pretreated leachate and membrane surfaces caused by the continuous increase in pH of pretreated leachate.