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Reverse osmosis


Key words dewatering, juice concentration, wine concentration, concentration, desalination, aroma rejection, flavour rejection, metal ions rejection, colourants rejection, hyperfiltration, reverse osmosis, cut-off, dealcoholization, purification, waste water treatment, membrane
Latest version 2011/01/10
Completed by Wageningen UR - FBR

How does it work?

Primary objective Separation
Working principle Reverse osmosis designates a membrane separation process, driven by a pressure gradient, in which the membrane separates the solvent (e.g. water, alcohol) from other components (e.g. aromas, metal ions, colours) of a solution. The selectivity of the membrane defines the separation process and depends mostly on membrane material. Commonly pore sizes are 1-10 Å (0.0001 - 0.001µm). pressures needed are 1380 – 6890 kPa (200 – 1000 psi, 15 – 70 bar). Permeate fluxes, which can be reached vary between 3 – 30 l/m2 h.
Additional effects Positive: Removal of microorganisms to a large extent

Negative: Also selective for undesired components

Important process parameters pressure, membrane type and material, surface properties of the membrane, surface area of the membrane, temperature, cross flow velocity
Important product parameters viscosity, particle concentration, diffusivity, density

What can it be used for?

Products Liquids, beverages, clarified juices
Operations Desalination, dealcoholisation, dewatering, concentration, purification
Solutions for short comings - Fouling of the membrane surface

- High water and cleaning detergents consumption during cleaning procedure - Wet storage of the membrane necessary - Pretreatment necessary (Clarification by NF/MF) - High concentrations are difficult to obtain due to the high osmotic pressures (one stage RO: 20 – 35◦Brix, two stage RO up to 40-50◦Brix)

What can it NOT be used for?

Products Solids, gas, high viscous liquids, non-clarified liquids
Operations Reverse osmosis is used for dewatering, but not for clarification (nanofiltration or microfiltration) Reverse osmosis can be used for pasteurization, but not for sterilization (NF or MF)
Other limitations Permeate fluxes are relatively low (3-30 l/m2 h)
Risks or hazards Careful cleaning is necessary, since reverse osmosis membranes need to be stored under wet conditions, which support the growth of microorganisms.


Maturity Lab-scale, pilot-scale and industrial scale possible
Modularity /Implementation Reverse osmosis can be inserted in an existing production line
Consumer aspects Not available
Legal aspects Not available
Environmental aspects Reverse osmosis energy consumption is low when compared with evaporation.

Further Information

Institutes University Twente - Membrane Technology Group, Johannes Keppler Universität Linz - Institut für Verfahrenstechnik
Companies Applied Membranes INC., MMS membrane Systems
References 1. Girard, B. and Fukumoto, L.R.; Membrane Processing of Fruit and Beverages: A review, Critical Reviews in Food Science and Nutrition, Volume 40, Issue 2, p. 91-157, 2000.

2. Baker, R. W.; Membrane Technology and Applications, 2nd edition, ISBN 0-470-85445-6, 2004.

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Created by Hamoen on 17 January 2012, at 12:23