Impact of pulsating flows on particle deposition in forward osmosis with spacers

Fouling continues to be a limiting factor in membrane processes. Pulsating feed flows have the potential to decrease fouling while maintaining a constant pressure drop over the module. This study quantifies the impact of pulsating flows on particle deposition in a forward osmosis system with spacers at a mean crossflow velocity of 14 cm s(-1) and permeate water flux of 18 L m(-2) h(-1). Carboxylate modified polystyrene beads were tracked by fluorescence microscopy in situ and real-time during the first 4 h of deposition with feed flow pulsations up to a frequency of 10 Hz, while experiments were conducted with a constant crossflow velocity as a reference. Imaging at 30 s intervals revealed deposition rates of up to 2.6 times higher at steady state, as compared to flow pulsations of 10 Hz. Consequentially, average deposition was reduced by a factor of 3.5 from steady state (109 +/- 67 beads mm(-2)) to pulsating feed flow (31 +/- 17 beads mm(-2)) after 4 h of deposition. The results of this research provide new fundamental insights related to the constraints and advantages of using pulsating flows for fouling mitigation in forward osmosis systems.

Automated summary

The study found that compared to pulsating flows, the deposition rate of particles can be up to 2.6 times higher in a steady state. As a result, the average deposition decreased by a factor of 3.5 from steady state (109 +/- 67 beads mm(-2)) to pulsating feed flow (31 +/- 17 beads mm(-2)) after 4 hours of deposition. These results provide new fundamental insights into the constraints and advantages of using pulsating flows for fouling mitigation in forward osmosis systems.