Hybrid processes for treatment of landfill leachate: Coagulation/UF/NF-RO and adsorption/UF/NF-RO

• Hybrid processes for treatment of stabilized landfill leachate is proposed.
• Coagulation/ultrafiltration and adsorption/ultrafiltration were pretreatment steps.
• Nanofiltration and reverse osmosis processes were used as final steps.
• RO/NF fouling was reversible therefore pretreatment was satisfactory.

Landfill leachate production and management are now recognized as one of the greatest problems associated with environmentally operation of sanitary landfills. In this study, laboratory-scale experiments were implemented to assess the effectiveness of coagulation/ultrafiltration (UF) and adsorption/UF as a pretreatment option for treating stabilized landfill leachate using nanofiltration (NF) and reverse osmosis (RO). Significant number of parameters was systematically monitored: chemical oxygen demand (COD), ammonium, turbidity, pH, total organic, inorganic carbon, total organic carbon (TOC), conductivity and concentrations of anions and metals. Coagulation showed better reduction of COD (65%), TOC (86%), and turbidity (87%) than adsorption (32%, −132%, 7%, respectively). Ultrafiltration was better after adsorption since reduction of COD and TOC was higher confirming that larger molecules were removed with coagulation and smaller with adsorption. Reduction of ammonium was relatively weak, for all pretreatment steps, in amount around 15%. XLE and NF90 membranes showed better performances than NF270 membrane due to tighter structure. Removal of COD and TOC was higher than 80% while for NF270 was 37% and 73%, respectively. Initial flux of RO/NF membranes declined between 45% and 72%. However, washing returned flux to almost initial flux showing that fouling wasn’t irreversible.