The membrane separation phenomenon is based on the presence of semi permeable membranes. The principle is easy: the layer acts as a very specific filter that will let water flow through, while it holds suspended solids and other substances.
Related Journals of Membrane Filtration:
Journal of Membrane Science & Technology, Filtration & Separation, Journal of Membrane Sciernce-Elsevier, IWA Water Wiki, Membrane Filtration-SS&WM, Membrane Water Treatment, Journal of Water treatment and Desalination.