Removal of inorganic charged micropollutants from drinking water supplies by hybrid ion exchange membrane processes

This study first illustrates the IEMB potential for the simultaneous removal of nitrate, perchlorate and bromate from drinking water. The removal of each of these pollutants to concentrations below the recommended levels for drinking water was successfully achieved. The initial development of the IEMB concept for the case of ionic mercury removal is then presented and discussed. For this purpose, appropriate cation exchange membranes were selected, and a suitable mixed microbial culture, capable of converting ionic mercury into elemental mercury, was obtained.

The results obtained show that the IEMB process allows for a simultaneous removal of different anionic pollutants (perchlorate, bromate and nitrate) present in water. Under the experimental conditions of this study (polluted water with 100 ppb of perchlorate and 60 ppm of nitrate) it was possible to produce 3.1 L/m2 h of drinking water with removal efficiencies of − − 96.5% for ClO4 and 99.6% for NO3 , without secondary contamination of the treated water by microbial cells and residual organic compounds. It is confirmed that the water treatment rate in the IEMB process does not depend on the pollutant biodegradation rate, but rather on the transport rate of the target pollutant through the membrane. Several cation exchange membranes (e.g. models from Fumatech and Selemion) proved to be good candidates for their implementation in the integrated IEMB process. An enriched microbial culture inoculated from sediment at the Tagus estuary showed promise in its ability to reduce ionic mercury to elemental mercury. Work is currently being performed on the evaluation of the potential of different carbon sources and on the kinetics of ionic mercury bioreduction before its integration according to the IEMB concept.