Desalination 199 (2006) 390–392 Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. Role of physico-chemical and hydrodynamic aspects in cleaning of spiral PES ultrafiltration membranes of dairy industry Murielle Rabiller-Baudry*, David Delaunay, Lydie Paugam, Lilian Bégoin, Bernard Chaufer Chimie et Ingénierie des Procédés, UMR 6226 CNRS “Sciences Chimiques de Rennes” Université Rennes 1– ENSCR, 263 avenue du général Leclerc, Campus Beaulieu Batiment 10 A, CS 74205, 35042 Rennes cedex, France email: murielle.rabiller-baudry@univ-rennes1.fr Received 17 October 2005; accepted 1 March 2006 1. Introduction Ultrafiltration (UF) of skimmed milk is widely used in order to control the protein content before the cheese making process. At industrial scale, UF is generally performed with spiral wound membranes of low cut-off (typically 5–10 kg mol –1 ) made of polyether- sulfone (PES). After water rinsing, an irre- versible fouling remained. Consequently, chemical cleaning is needed in order to restore the flux. At industrial scale, the step of cleaning (and further disinfection) is daily performed via cleaning in place (CIP) sta- tions, running in empirical and non-optimised conditions and, finally, the recovered flux is lower than that of the virgin membrane. As a consequence, a progressive decrease of flux during UF of dairy fluids is observed over fol- lowing months of production. The general cleaning scheme was performed at 50°C in two steps: first an alkaline solution at pH = 11.5 known to be efficient toward organic matter and then a cleaning with an acid solu- tion at pH = 1.6 to remove mineral matter. As the main target of cleaning is protein, the gen- eral scheme of cleaning/disinfection can be reduced to a single alkaline step limiting thus water consumption for rinsing and produced volume of effluents. The flux is not always reliable as it can be modified independently of the cleaning efficiency by adsorption of com- ponents (surfactants, nitrates) of the cleaning solution. In this context, the aim of this study is first to propose physico-chemical parame- ters to have an access to the effective cleaning efficiency, to identify parameters governing the cleaning and propose a guide to formulate an adapted and optimised alkaline cleaning solution. Two physico-chemical criteria were proposed: the first is based on the quantifica- tion of irreversible fouling, by FTIR-ATR, directly on the membrane and the second on interfacial energy of detergents. The cleaning *Corresponding author. doi:10.1016/j.desal.2006.03.210 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V.