Reverse Electrodialysis (RED) is one of the most promising technologies to convert salinity gradient chemical energy into electricity. RED units are traditionally operated with natural streams as river water and seawater thereby limiting the spread of the technology in sites far from coastal areas. Aim of the present work is that of exploring and expanding feed possibilities for RED systems by employing waste streams. Thus, an experimental study was performed by testing, for the first time, a Reverse Electrodialysis (RED) unit fed with a high salinity wastewater originated in a fish canning factory, and a low salinity wastewater from a sewage treatment plant. Uninterrupted, long duration experiments were carried out to evaluate time-evolution of the key electrical parameters. Power output was monitored over time along with pumping losses and electrical resistance. The effect of chemical backwashing was analysed in order to assess process maintenance. Results showed that fouling issues have a crucial impact on process performance and should be properly addressed before operating RED units fed by waste streams.