Reduction of energy consumption and auxiliary use are main objectives in industry as environmental legislation and international treaties become stricter. To improve energy-consuming evaporation and drying steps, a pre-treatment step using nanofiltration (NF) can be considered. Energy and auxiliary use can be reduced in this way. Despite the advantages of NF, its application in chemical and food industry is still very limited. Major reasons for this are the non-aqueous environment of the process and the lack of knowledge on long-term stability and performance of polymeric NF-membranes in these media. The research will focus on determination of long-term stability and performance of polymeric membranes. To establish these parameters a generally applicable membrane characterization method will be developed, which is independent of the solvent applied. Additionally, swell-sorption measurements at various pressures will be made. Membrane characteristics, swell-sorption results, stress-strain models and mass transfer models will be used to establish the factors that determine long-term stability and performance of commercially available NF-membranes. This information will give insights and guidelines for the development of robust NF-membranes and membrane processes in chemical and food industry. This offers the possibility of reducing energy and auxiliary consumption.