Desalination 212 (2007) 1–14 *Corresponding author. Fouling in a high pressure, high recovery rotating reverse osmosis system Cynthia L. Pederson, Richard M. Lueptow* Department of Mechanical Engineering, Northwestern University, 2145 N. Sheridan Rd., Evanston, IL 60208, USA Tel. +1 (847) 491-4265; Fax +1 (847) 491-3915; email: r-lueptow@northwestern.edu Abstract Concentration polarization and membrane fouling have limited the efficiency of reverse osmosis. Rotating filtration may minimize the effects of concentration polarization and membrane fouling by increasing the shear at the membrane surface. A second-generation high-pressure rotating reverse osmosis device was designed to perform long-term tests of the purification of a complex wastewater ersatz based on what is expected to be produced on a long-term space mission. A significant amount of fouling occurred after three days of operation during the tests. The fouling potential was used to characterize this fouling and was incorporated into a theoretical model of rotating reverse osmosis. The effect of cleaning cycles and a biocide on the reduction of flux due to fouling was investigated. Cleaning cycles every 48 h significantly improved the flux of the device. The addition of a biocide reduced the fouling including the sharp decrease in flux at day three, which can therefore be attributed to biofouling of the membrane surface. Keywords: Rotating filtration; Reverse osmosis; Biofouling; Fouling potential; Wastewater reclamation 1. Introduction A rotating reverse osmosis system consists of an inner porous cylinder supporting a reverse os- mosis membrane that rotates within an outer sta- tionary cylindrical shell. Initial tests of rotating reverse osmosis (RRO) have indicated that the approach may reduce concentration polarization, increase recovery, and minimize scaling for re- verse osmosis (RO) [1–3]. Previous investigations of rotating microfil- tration (using a microporous membrane rather than an RO membrane) suggested that the high shear at the membrane surface due to rotation reduces the fouling of the filtration media [4,5]. This is most likely due to the increased shear at the mem- brane surface due to Taylor–Couette flow. As the membrane rotates, instabilities known as Taylor 0011-9164/07/$– See front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.desal.2006.10.001 Received 22 December 2005; accepted 19 October 2006