Leachate treatment by ceramic ultrafiltration membranes: fouling mechanisms identification

The treatment of leachate is a complex process that involves the use of various treatment methods in order to achieve acceptable quality levels. The objective of this study is to investigate the impact of transmembrane pressure (TMP) at a constant flow velocity (V = 2m/s) on the treatment of leachate from the controlled landfill of Oum Azza, Rabat, Morocco, as well as on the fouling mechanism of three ultrafiltration (UF) ceramic membranes (UF20, UF50, and UF100) with varying porosities of 20, 50, and 100 nm. The experiments were conducted using a semi-industrial pilot plant provided by the French Company TIA (Techniques Industrielles Appliquees), which was equipped with a ceramic membrane. Two mathematical models, the Hermia model and the Bolton model, were used to identify the fouling mechanisms of the tested membranes. The Hermia model provides four equations that describe the four fouling modes, namely cake formation, intermediate blockage, pore constriction, and complete blockage. Furthermore, the Bolton model combines these fouling mechanisms to determine whether fouling is caused by adsorption, occlusion, or compression of the filter layer. The results indicate that the permeate and rejection of pollution indicators (chemical oxygen demand, 5-day biochemical oxygen demand, and total suspended solids) for the three tested membranes are affected by the TMP. The UF20 membrane showed the best rejection rates, followed by UF50 and finally UF100. For permeate flow, UF100 > UF50 > UF20. According to the Hermia model, the fouling of all three membranes was superficial, with the main fouling mechanisms being cake formation or intermediate blockage. Application of the Bolton model equations revealed that fouling of the UF20 and UF50 membranes was described by the combined equation of cake formation and complete blockage. For the UF100 membrane, fouling was described by the combined equation of cake formation and intermediate blockage.