Mutrees - Membrane Distillation

Membrane distillation

Membrane distillation, also called pervaporation, is a method for the separation of mixtures of liquids by partial vaporization through a non-porous or porous membrane. The name of this membrane-based process is derived from the two basic steps of the process, firstly the permeation through the membrane by the permeate, then its evaporation into the vapor phase. This process is used by a number of industries for several different processes, including purification and analysis, due to its simplicity and in-line nature.

Membrane distillation (MD) is a thermally driven process, in which only vapor molecules are transported through porous hydrophobic membranes. The liquid feed to be treated by MD must be in direct contact with one side of the membrane and does not penetrate inside the dry pores of the membranes. The hydrophobic nature of the membrane prevents liquid solutions from entering its pores due to the surface tension forces. As a result, liquid/vapor interfaces are formed at the entrances of the membrane pores.

TNO has developed a membrane distillation method, called Memstill®. This technique uses waste heat for the MD driving force, due to transmembrane vapor pressure difference.


Sea water desalination

Seawater is becoming an increasingly important source for our water production. More than 97% of the world’s water is seawater. In densely populated areas in particular, demand for healthy drinking water is growing steadily. Together with several industrial partners TNO has developed Memstill®, a technology that takes salty seawater and makes it clean and drinkable.

Memstill is a distillation method that makes use of membranes. Concentrated seawater (brine) forms a residue and the clean drinking water is evaporated by the membrane and captured. Industrial residual heat (< 90°C) is used, a source that is available in abundance all over the western world. In other areas solar heat can be employed. In both cases the technology produces negligible greenhouse gas.

Process water cleaning

Finally, Memstill® also offers industry an attractive proposition. Industrial water can be made even purer than drinking water, and very pure process water with conductivity of less than 1µS/cm makes for many applications in industry as pure water.


Mutrees has contact with suppliers of Membrane distillation technologies for both (sea) water desalination as well as process water cleaning, and can consult in the application of these technologies.

© 2010 D.F.Mulder