In the beverage industry, numerous alkaline solutions are generated in cleaning processes. The treatment of these alkaline cleaning solutions with the objective of recovery or improvement of their quality can be conducted using pressure-driven membrane processes. This paper focuses on the behaviour of additive components, used for the alkaline cleaning of returnable bottles, during filtration with pH-stable ultrafiltration (UF) and nanofiltration (NF) membranes. A flux decline, which was more pronounced initially, was observed for the UF membranes with a cut-off of 1 and 50 kDa. This can be attributed to concentration polarisation at the membrane surface and the adsorption of cleaning additive components, especially of a non-ionic surfactant. The most stable membrane permeability during filtration was achieved by a 0.2 kDa NF membrane. The UF membrane with a cut-off of 50 kDa showed the lowest rejection for the different cleaning additives (5-20%), whereas the NF membrane with a cut-off of 0.2 kDa showed the highest rejection (about 90%) for all cleaning additives. (C) 2002 Elsevier Science B.V. All rights reserved.