New lives for old reverse osmosis (RO) membranes Original Research Article

The overall objective of the present work was to estimate by membrane autopsy the level of performances degradation of old reverse osmosis (RO) membranes/modules in order to envisage their reuse. A mechanistic approach using the Spiegler–Kedem–Katchalsky model helps us to observe that the old RO membrane acquired a convective mass transfer. We defined a novel Peclet number (denoted Pe′) usable to distinguish between diffusional and convective mass transfer. We observed that for the old membrane Pe′ numbers are always higher than 1. Furthermore, SEM/AFM and EDX experiments show crystals and bacteria particles as fouling agents, roughness increase for the old membrane (from 73 to 220 nm) due to foulants deposition. EDX experiments demonstrated that FexOy crystals are dominant. SP measurements help us to observe a displacement of the isoelectric point (IEP) for the virgin membrane from 2.7 ± 0.3 to 4.6 ± 0.3 in comparison to the old one showing chemical modifications of the inner active layer suspected due to biofouling residuals. In the last part and for the first time, module materials reuse occurred in the place of their incineration as geotextile in proper home garden.