AFM has been proved to be a rapid method of assessing membrane-solute interactions (fouling) of membranes under process conditions. The interactions of developmental membranes (SPEEWPSU and PSU) with different solutes have been directly measured and linked to process performance. Correlation of the performance of two commercial PC1 membranes (ES404 and EM006) with AFM measurements has been carried out for two types of separation of industrial importance: ultrafiltration in the pulp and paper industry and protein concentration/ fractionation. Al34 expertise has been further exploited in a study of the efficiency of membrane cleaning after a process of whey concentration.