Removal of radionuclides in drinking water by membrane treatment using ultrafiltration, reverse osmosis and electrodialysis reversal M. Montaña a, * , A. Camacho a , I. Serrano a , R. Devesa b , L. Matia b , I. Vallés a a Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya, ETSEIB Diagonal 647, 08028 Barcelona, Spain b Aigües de Barcelona, AGBAR. Laboratory, General Batet, 5-7, 08028 Barcelona, Spain article info Article history: Received 31 May 2012 Received in revised form 17 December 2012 Accepted 6 January 2013 Available online 29 January 2013 Keywords: Removal radioactivity Gross alpha activity Ultrafiltration Electrodialysis reversal Reverse osmosis abstract A pilot plant had been built to test the behaviour of ultrafiltration (UF), reverse osmosis (RO), and electrodialysis reversal (EDR) in order to improve the quality of the water supplied to Barcelona met- ropolitan area from the Llobregat River. This paper presents results from two studies to reduce natural radioactivity. The results from the pilot plant with four different scenarios were used to design the full- scale treatment plant built (SJD WTP). The samples taken at different steps of the treatment were analysed to determine gross alpha, gross beta and uranium activity. The results obtained revealed a significant improvement in the radiological water quality provided by both membrane techniques (RO and EDR showed removal rates higher than 60%). However, UF did not show any significant removal capacity for gross alpha, gross beta or uranium activities. RO was better at reducing the radiological parameters studied and this treatment was selected and applied at the full scale treatment plant. The RO treatment used at the SJD WTP reduced the concentration of both gross alpha and gross beta activities and also produced water of high quality with an average removal of 95% for gross alpha activity and almost 93% for gross beta activity at the treatment plant. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Clean water, free of toxic chemicals and pathogens, is essential to human health. Common treatment methods used at waterworks are a combination of chemical oxidation, coagulation-flocculation, sand filtration and disinfection. However, in recent years, mem- brane technology has become an extraordinarily useful tool for the desalination of seawater, and this technology is also being increasingly used in the production of freshwater. Recent advances suggest that many issues involving water quality could be resolved or greatly ameliorated by using ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), electrodialysis (ED) or electrodialysis reversal (EDR) processes. UF and NF membrane filtration processes work by excluding contaminants using pore size constrains when water under pressure is forced to pass through a semi-permeable membrane with different pore sizes. Both the pore size and applied pressure must be adequate for the required purposes. The RO membrane works as a molecular filter that rejects pos- itively and negatively charged ions based on molecular weight when pressurized water is forced through the membrane. In con- trast, the driving force for separation in ED and EDR processes is an electric potential, and an applied current is used to transport ionic species across selectively permeable membranes. The principal difference between ED and EDR is that EDR includes the additional step of a change in electrode polarity every 15e20 min, thus causing a reversal in ion movement. This step minimizes scale buildup on the membranes which means that EDR can operate for longer time periods between cleanings. Van der Bruggen and Van der Casteele (2003) have reviewed the use of NF to remove cations, natural organic matter, biological contaminants, organic pollutants, nitrates and arsenic from groundwater and surface water. The UF process is also used for purification of water contaminated by toxic metal ions, radionu- clides, organic and inorganic solutes, bacteria and viruses. For example, ultrafiltration assisted by complexation has been used to reduce uranium concentration (Kryvoruchko et al., 2004). An NF pilot plant experiment was set up to determine the uranium removal efficiency and for most experiments the uranium removal was about 95% (Raff and Wilken, 1999). In another study (Favre- Réguillon et al., 2008) demonstrated that uranium rejection depended on the uranyl species. In addition, RO effectively removes many inorganic contaminants, including many toxic metals and radionuclides, such as radium and uranium (Huikuri et al., 1998). RO can remove 87e98% of radium from drinking water and similar elimination can be achieved for alpha, beta and photon emitters * Corresponding author. Contents lists available at SciVerse ScienceDirect Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad 0265-931X/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvrad.2013.01.010 Journal of Environmental Radioactivity 125 (2013) 86e92