Objective of this study was to conduct a baseline study of osmotic membrane bioreactor (OMBR) -
optimization of operating conditions in forward osmosis (FO). Experiments were conducted with an FO pilot system. Tap
water was used as the feed and NaCl and MgSO4 solutions were used as draw solution. Effects of various operating
conditions on flux have been investigated. In addition, pure water permeability of the FO membrane was tested. It was
observed that the plant operation could be stablized within 1 h. When the membrane selective layer faced to the feed, a
flux of 6.3 lm-2h-1 (LMH) was achieved at 24 atm osmotic pressure and 25 °C and effects of feed velocity and air velocity
on flux were not siganificant under the testing conditions due to low external concentration polarization (ECP). However,
when the selective layer faced to the draw solution, the flux was enhanced by 64% due to much reduced internal
concentration polarization (ICP), the flux sharply increased with an increase in velocity of the draw solution in the laminar
flow pattern range due to a countable effect of dilutive external concentration polarization (DECP) and leveled off after
the flow pattern became turbulent. NaCl performed much higher efficiency than MgSO4 as an osmotic agent due to a
greater solute diffusion coefficient of NaCl.
Effect of Internal and External Concentration Polarizations on the Performance of Forward Osmosis Process
