Publications (3)1.12 Total impact
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Article: The innovative osmotic membrane bioreactor (OMBR) for reuse of wastewater.
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ABSTRACT: An innovative osmotic membrane bioreactor (OMBR) is currently under development for the reclamation of wastewater, which combines activated sludge treatment and forward osmosis (FO) membrane separation with a RO post-treatment. The research focus is FO membrane fouling and performance using different activated sludge investigated both at laboratory scale (membrane area of 112cm2) and at on-site bench scale (flat sheet membrane area of 0.1 m2). FO performance on laboratory-scale (i) increased with temperature due to a decrease in viscosity and (ii) was independent of the type of activated sludge. Draw solution leakage increased with temperature and varied for different activated sludge. FO performance on bench-scale (i) increased with osmotic driving force, (ii) depended on the membrane orientation due to internal concentration polarization and (iii) was invariant to feed flow decrease and air injection at the feed and draw side. Draw solution leakage could not be evaluated on bench-scale due to experimental limitation. Membrane fouling was not found on laboratory scale and bench-scale, however, partially reversible fouling was found on laboratory scale for FO membranes facing the draw solution. Economic assessment indicated a minimum flux of 15L.m-2 h-1 at 0.5M NaCl for OMBR-RO to be cost effective, depending on the FO membrane price.Water Science & Technology 01/2011; 63(8):1557-65. · 1.12 Impact Factor -
Article: Membrane fouling and process performance of forward osmosis membranes on activated sludge
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ABSTRACT: An innovative osmotic membrane bioreactor (OMBR) is currently under development, based on forward osmosis (FO) driven by an osmotic pressure difference. For the OMBR to be both technically and economically viable, the performance of the FO membranes has to be sufficiently high, while membrane fouling and draw solution leakage has to be low. The effect of temperature, membrane type, membrane orientation, type and concentration of draw solution was investigated to optimize FO membrane performance using deionised water. Membrane fouling and draw solution leakage was investigated in this work by laboratory scale FO experiments using an activated sludge solution from a membrane bioreactor (MBR).The best FO performance with an activated sludge solution was found with a FO-type membrane (J = 6.2 l/m2 h at 20 ± 2 °C with 0.5 M NaCl corresponding to π = 24 bar). Draw solutions from salts consisting of monovalent ions (NaCl and NaNO3) performed better than salts consisting of bivalent ions (MgSO4 and ZnSO4), while the flux of the FO membrane were non-linearly related to the concentration of the draw solution. Internal concentration polarization did hamper the FO performance as a result of the thickness and structure of the porous substructure of the investigated membranes.Both reversible and irreversible membrane fouling were not found during the FO experiments using activated sludge solutions. Furthermore no substantial draw solution leakage was found for the FO membranes at various draw solution concentrations for different draw solutions.Journal of Membrane Science. -
Article: Optimization of operating conditions in forward osmosis for osmotic membrane bioreactor
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ABSTRACT: 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 MgSO 4 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 -2 h -1 (LMH) was achieved at 24 atm osmotic pressure and 25 ºC 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 MgSO 4 as an osmotic agent due to a greater solute diffusion coefficient of NaCl.
