Effect of intermittent pressure-assisted forward osmosis (I-PAFO) on organic fouling

- Intermittent relaxation in PAFO is helpful for preventing severe membrane fouling.
- I-PAFO shows higher water productivity and lower fouling tendency than PAFO.
- I-PAFO reduces membrane area and operating energy required compared to PAFO.
- I-PAFO has the possibility to be employed in FO-RO hybrid processes in an I-PAFO-RO configuration.

This study investigated the feasibility of intermittent pressure-assisted forward osmosis (I-PAFO) operation for organic fouling mitigation, using sodium alginate as the model foulant. FO and PAFO were also operated to compare system performances in terms of water flux behavior, flux recovery by physical cleaning, fouling propensity, energy consumption, and membrane area required. Results showed that I-PAFO obtained higher water flux and flux recovery by physical cleaning than PAFO because of its lower fouling tendency. I-PAFO was able to reduce not only the accumulated foulant mass on the membrane surface, but also fouling layer compaction through the intermittent pressurization. Furthermore, it displayed benefits in terms of reducing membrane area required and operating energy compared to PAFO, due to its higher water productivity and sustainability. Therefore, I-PAFO can be a plausible option for saving membrane costs and operating energy when FO operations are concerned particularly in accordance with hybridization with RO (i.e. I-PAFO-RO hybrid process).