You can find a nice review of pros and cons of Membrane Distillation here:

http://jnasci.org/wp-content/uploads/2013/12/1072-1075.pdf

It is a promising water desalination process

Dear colleague,

I will publish as soon as possible a paper related to this subject. There are many variables which involved in this process "distillation". I believe also that the manufacturer of the membrane cannot give a datailed answer to this question.

Kind regards!

Dear Khaled, maybe this helps:

https://www.ises.org/fileadmin/user_upload/Webinar_presentations/Joachim_Webinar_ISES_20150128.pdf

https://www.hindawi.com/journals/isrn/2011/523124/

best regards

Johannes

Dear Khaled:

In my opinion, MD has so many parameters and less mathematical constraints. So, it is not a matter of thickness. Before any experimental or theoretical research, what to definitely know is how much (waste) heat is steadily available with reasonable price. 

As you know, if you decrease membrane thickness, you should also decrease thermal conductivity of the membrane. This is because thinner membrane transfer heat energy more than thicker membrane. So, you have less heat energy left for evaporation. 

Albert

Thanks my dear colleagues for your interesting comments.

In my opinion, it is a matter of collaboration between a research efforts and membrane manufacturers. They should come up with a special membrane that is more suitable for distillation. however, the thickness optimisation means less mass transfer resistance and higher thermal energy-efficient. However using low cost energy like waste heat can be significant solution at this stage.