Unrevealing biofouling in a solar-powered membrane distillation process operated with intermittent mode

Fouling in membrane distillation processes has been investigated primarily in terms of inorganic scaling under continuous operating conditions. This study investigated biofouling in a solar-powered membrane distillation (SPMD) process operated in intermittent mode to simulate the sustainable operation of an MD system coupled with renewable energy. The intermittent SPMD process was evaluated at feed temperatures of 25 and 55 °C using two membrane types, polytetrafluoroethylene (PTFE)/polypropylene (PP) bi-composite and modified photothermal membranes; and with and without simulated solar irradiation. The SPMD system was operated at an optimal flow rate of 250 mL/min and solar irradiation intensity of 1 sun (1 kW/m²). More severe biofouling was observed at 55 °C than at 25 °C. Solar irradiation did not significantly affect biofouling on the MD membranes. The photothermal membrane remained unfouled under the biofouling conditions tested. Both bacterial and eukaryotic community structures varied with operational temperature and membrane type but were less affected by solar irradiation under the tested conditions. Several bacterial taxa associated with biofouling were identified under each operating condition, with halotolerant bacteria with biofilm-forming potential becoming predominant on the membrane surfaces. In addition, several uncultured eukaryotic clones originating from marine environments were found as core members of the eukaryotic communities associated with biofouling.