Fouling fractionation in reverse electrodialysis with natural feed waters demonstrates dual media rapid filtration as an effective pre-treatment for fresh water

Reverse electrodialysis (RED) is a process to harvest renewable energy from the salinity gradient obtained by the controlled mixing of river and seawater. When using natural waters, (bio)fouling is an inevitable process which has a negative impact on the obtained power density. Specific characteristics of RED do not allow the direct transfer of knowledge from previous fouling studies in other membranes process. More insight on how fouling is impacting RED is needed to design effective pre-treatment solutions. In this study, fresh water was fractionated based on particle size for 54 days, revealing the impact that specific foulants have on the RED process. A combination of turbidity and particle size measurements coupled with stack performance throughout the experiment showed that particles with an average diameter of 10 mu m are responsible for a reduction in obtained stack power density of around 25%. Visualization of extracellular microbial polymers by confocal laser scanning microscopy confirmed that the role of biofouling only was of lesser concern compared to the impact of these suspended particles. According to these results, the removal of suspended particles >10 mu m using a dual media filter has shown to be a simple and effective pre-treatment for fresh water in RED applications.