Reducing fouling and boundary-layer by application of helical flow in ultrafiltration module employed for radioactive wastes processing Gra _ zyna Zakrzewska-Trznadel a *, Marian Harasimowicz a , Agnieszka Mi  skiewicz a , Agnieszka Jaworska a , Ewa Dluska b , Stanislaw Wro nski b a Department of Nuclear Methods in Process Engineering, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland Tel. +4922 5041214; Fax +48228111532; email: gzakrzew@ichtj.waw.pl b Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, 00-645 Warsaw, Poland Received 31 July 2007; revised 12 October 2007; accepted 19 October 2007 Abstract Application of helical Couette  Taylor flow (CTF) for reduction of membrane fouling in the process of radioactive wastes treatment was considered. The experiments were carried out with model solutions of cobalt ions (Co 2+ ). Ultrafiltration process combined with complexation with polyacrylic acid or adsorption on activated carbon seeds was applied. The influence of hydrodynamic conditions in the module on the permeate flux and separation efficiency was tested. It was noticed that the helical flow influenced filtration efficiency: with increase of rotation frequency of the inner cylinder in the module, up to 3-fold enhancement of permeate flux was observed. The estimated thickness of residual polymer layer developed on the membrane surface depended on rotation frequency, too. Slight increase of retention factors was observed when dynamic conditions were applied. Keywords: Ultrafiltration ; Complexation; Radioactive wastes; Fouling; Helical flow 1. Introduction Pressure-driven membrane filtration is an important process for separation of colloids and particulate matter from liquid suspensions in many fields of engineering and applied science. There are many examples of application of pressure-driven membrane techniques in nuclear technology. Such methods like reverse osmosis, Presented at the Third Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Siofok, Hungary, 2–6 September 2007. *Corresponding author. Desalination 240 (2009) 108  116 0011-9164/09/$– See front matter # 2009 Elsevier B.V. All rights reserved. doi: 10.1016/j.desal.0000.00.000