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Two-phase system to enhance UF
News and Views peroxide followed b y nitric acid gave a negative flux recovery, which could be explained by a ligand exchange model. It was s h o w n overall that the performance of the digester was greatly improved with m e m b r a n e pretreatment, particularly in the case of naked barley b a s e d stillage.
Further Informatlon from: Chung-Hak Lee, Department of Chem/cal Technology, College of Engineering, Seoul National University, Seoul 151-742, South Korea. Vl
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particular, the influence of m e m b r a n e orientation was investigated. On the addition of air to the liquid stream, permeate flux was observed to increase by u p to 60% for dextran, 113% for dyed dextran and 91% for BSA. The rejection ratios were also improved with an increase of between 5 a n d 10%. It was found that, for the experimental range explored here, the greater e n h a n c e m e n t s occurred at higher feed concentration. Vertically m o u n t e d m e m b r a n e s showed a 10--20% higher permeate flux w h e n compared with horizontally installed m e m b r a n e s u n d e r the same two-phase operation. It was suggested that this was due to a combination of the b o u n d a r y layer disruption a n d increased crossflow velocities at the m e m b r a n e surface.
Further Informatlon from: Z.F. Cul, Department of Chemical Engineering, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JL, UK. m
N e w RO e l e m e n t s for h o t w a t e r sanitizing rccitcuhUion l~ap
~PURP
Schematic dWLgram of laboratory-scale apparatus for testing ceramic membranes for the pretreatment of alcohol distillery wastes.
Desalination Systems, Inc h a s Just released its D u r a t h e r m TM,spiral w o u n d m e m b r a n e elements for high temperature reverse osmosis applications. Previously, RO was limited b e c a u s e spirals could not withstand process temperatures above 50°C. Further, elements could not be sanitized without the use of chemicals, says the company. D u r a t h e r m provides reliable performance at c o n t i n u o u s operating t e m p e r a t u r e s to 70°C a n d at intermittent, low p r e s s u r e hot water sanitizing cycles to 90°C. As a result, RO s y s t e m s can now be used effectively in higher temperature process streams a n d in the ultrapure water a n d food processing industries.
Two-phase system to e n h a n c e UF In a recent issue of the Journal of Membrane Science, (90, pp 183-189, 1994), a m e t h o d for reducing concentration polarization a n d m e m b r a n e fouling by injecting air into the feed stream in crossflow ultraflltration is proposed. A two-phase flow across the m e m b r a n e surface is created, a n d addition of air to the liquid stream increases both the turbulence at the surface of the m e m b r a n e a n d the superficial crossflow velocity within the system, s u p p r e s s i n g b o u n d a r y layer formation, thereby e n h a n c i n g the filtration process. In these experiments a range of different test solutions (dextran, dyed dextran a n d bovine s e r u m albumin) u n d e r different flow a n d pressure conditions were ~ e d u s i n g a tubular membrane. In
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Splral-wound membrane element from Desalination Systems.
M e m b r a n e Technology No. 48
Further Informatlon from: Chung-Hak Lee, Department of Chem/cal Technology, College of Engineering, Seoul National University, Seoul 151-742, South Korea. Vl
-@
particular, the influence of m e m b r a n e orientation was investigated. On the addition of air to the liquid stream, permeate flux was observed to increase by u p to 60% for dextran, 113% for dyed dextran and 91% for BSA. The rejection ratios were also improved with an increase of between 5 a n d 10%. It was found that, for the experimental range explored here, the greater e n h a n c e m e n t s occurred at higher feed concentration. Vertically m o u n t e d m e m b r a n e s showed a 10--20% higher permeate flux w h e n compared with horizontally installed m e m b r a n e s u n d e r the same two-phase operation. It was suggested that this was due to a combination of the b o u n d a r y layer disruption a n d increased crossflow velocities at the m e m b r a n e surface.
Further Informatlon from: Z.F. Cul, Department of Chemical Engineering, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JL, UK. m
N e w RO e l e m e n t s for h o t w a t e r sanitizing rccitcuhUion l~ap
~PURP
Schematic dWLgram of laboratory-scale apparatus for testing ceramic membranes for the pretreatment of alcohol distillery wastes.
Desalination Systems, Inc h a s Just released its D u r a t h e r m TM,spiral w o u n d m e m b r a n e elements for high temperature reverse osmosis applications. Previously, RO was limited b e c a u s e spirals could not withstand process temperatures above 50°C. Further, elements could not be sanitized without the use of chemicals, says the company. D u r a t h e r m provides reliable performance at c o n t i n u o u s operating t e m p e r a t u r e s to 70°C a n d at intermittent, low p r e s s u r e hot water sanitizing cycles to 90°C. As a result, RO s y s t e m s can now be used effectively in higher temperature process streams a n d in the ultrapure water a n d food processing industries.
Two-phase system to e n h a n c e UF In a recent issue of the Journal of Membrane Science, (90, pp 183-189, 1994), a m e t h o d for reducing concentration polarization a n d m e m b r a n e fouling by injecting air into the feed stream in crossflow ultraflltration is proposed. A two-phase flow across the m e m b r a n e surface is created, a n d addition of air to the liquid stream increases both the turbulence at the surface of the m e m b r a n e a n d the superficial crossflow velocity within the system, s u p p r e s s i n g b o u n d a r y layer formation, thereby e n h a n c i n g the filtration process. In these experiments a range of different test solutions (dextran, dyed dextran a n d bovine s e r u m albumin) u n d e r different flow a n d pressure conditions were ~ e d u s i n g a tubular membrane. In
6
Splral-wound membrane element from Desalination Systems.
M e m b r a n e Technology No. 48