Effect of landfill leachate ageing on ultrafiltration performance and membrane fouling behaviour

In this study, the effect of ageing on the performance and fouling mechanisms in the ultrafiltration of landfill leachates using titania-zirconia (ZrO2-TiO2) tubular membrane was thoroughly studied. Results revealed that the maturation of the leachate has a positive effect on its ultrafiltration, with a twofold higher final permeability compared with the young one. This is the result of the higher organic load, particularly that corresponding to proteins and carbohydrates, of the young leachate. Resistance-in-series analysis demonstrated that the loss of permeability was mainly due to reversible fouling, caused by cake filtration. Either irrecoverable or irreversible fouling were scarce and not conditioned by the stage of maturation of the leachate. Chemical oxygen demand (COD) rejection for the mature leachate varied with volume concentration ratio (VCR) following an approximately sigmoidal shape, from an initial value of 18.5% to a final one of 49.6%, with the faster increase at VCR ranging from 1.2 to 1.7, due to the permeation of fatty acids by the ultrafiltration (UF) membrane. On the other hand, COD rejection remained approximately constant at 48% during the ultrafiltration of the young leachate, which can be attributed to the presence of higher molecular weight compounds in its composition.