Diagnosis of small capacity reverse osmosis unit for desalinated tap water

AbstractTunisian norms for drinking water tolerates a maximum TDS of 1.5 g/L and the domestic water presents usually salinity greater than 500 mg/L. In the last years, several small capacity reverse osmosis desalination prototypes have been marketed. The RO unit used in this research produces 10–15 L/h of treated water with a recovery rate between 25 and 40% and salt rejection in the order of 90%. The salinity of the tested domestic water is between 0.4 and 1.4 g/L. Water pretreatment is composed of three filtration operations (cartridge filter, granulate active carbon filter, and 5 μm cartridge filter). Pretreated water is pumped through RO membrane with a maximum pressure of 6 bars. At the 4th year, the RO unit’s performance was substantially decreased. The recovery rate and salt rejection fall down about 50 and 100%, respectively, and the pressure drop increases from 1 to 2.1 bars. An autopsy of the used RO membrane was done by different analysis techniques such as SEM/EDX, AFM, XRD, and FTIR spectrosc...