Proc. Int. Conf. PERMEA 2003, Tatranské Matliare, Slovakia, Sept. 7-11, 2003 Removal of trace mono-valent inorganic pollutants using the Ion Exchange Membrane Bioreactor concept Svetlozar Velizarov , Cristina Matos, Ana Sequeira, Maria Reis, João Crespo CQFB / REQUIMTE, Department of Chemistry, FCT, Universidade Nova de Lisboa, P-2829-516 Caparica, Portugal; Phone/fax: +351 21 294 8385, E-mail: velizarov@dq.fct.unl.pt Keywords: ion exchange membranes, membrane bioreactor, drinking water, water treatment, perchlorate, nitrate Abstract The ion exchange membrane bioreactor (IEBM) concept is based on the use of a non-porous mono- ion permselective membrane, which acts as a barrier between the water stream, containing one or more target mono-valent inorganic pollutants, and a biological compartment, containing a microbial culture able to degrade (transform) these pollutants to harmless products. In this work, the possibility of removing polluting ions in trace levels is addressed for conceptually different situations: 1 - simultaneous removal of perchlorate and nitrate from low salinity drinking water streams, if ClO 4 - is present as a trace counter-ion (in the ppb concentration range) with respect to NO 3 - ; 2 - nitrate removal from high-salinity multi-ionic water used in sea aquariums. The results obtained showed that ClO 4 - and NO 3 - ions may be efficiently transported and reduced to harmless Cl - and N 2 providing that the IEMB operating conditions are properly selected. Furthermore, the simultaneous removal of perchlorate was possible even if the concentration of nitrate in the water stream is about three orders of magnitude higher than that of perchlorate, thus considerably extending the possible applications of the IEMB concept for the treatment of water streams containing undesired trace charge compounds. Introduction Perchlorate in drinking water supplies represents a serious concern and its possible removal has been the subject of considerable recent research efforts. Perchlorate can interfere with the production of human thyroid hormones [Christen, 2000] and, therefore, a provisional action level of 18 µg/L for perchlorate in drinking water has been already established by some agencies in USA [Susarla et al, 1999]. The primary sources of perchlorate contamination are industrial operations and military units using ClO 4 - as an oxidising agent in the form of ammonium, sodium, and potassium salts. Perchlorate has been identified also in fertilisers [Susarla et al., 1999]. Perchlorate is exceedingly 1