Reversible fouling by particulate matter from natural seawater reduces RED performance while limiting biofouling

Reverse Electrodialysis (RED) has shown to be a promising technology for electricity production but membrane fouling can influence the energy yield, thus, it is crucial to gain knowledge on the impact and prevention of fouling. We used a sequence of pre-treatments (dual-media filter, microfilter and activated carbon filter) to fractionate foulants in seawater based on size and investigated its effect on RED. Fouling reversibility was studied by applying a cleaning procedure with reversal and increased flow and air sparging at the end of the experiment. After 63 days of operation, when using only the dual-media filter as pre-treatment, the pressure drop increased by 520 mbar in the seawater compartments without affecting the electrochemical measurements. The application of the cleaning procedure allowed to recover 90 % of the pumping power losses. A membrane autopsy showed the development of a biofilm layer on the membrane of the stacks receiving the most treated water while it was not detected when only the dual-media filter was used, which showed that the presence of particulate matter could help limit biofouling development. Together with the performance recovery, we concluded that the application of the dual media filtration system is a suitable and cost effective pre-treatment for RED.