We have utilized RO ...

We have utilized RO membranes for extraction of reuse quality water from effluents in a number of cases. The extracted water in some cases was to be used for fermentation purpose. The production chemists were skeptic about suitability of such recovered water for fermentation, fearing contamination. In view of their reluctance, we carried out special microbiological analysis of the same. We found that immediately after emergence of permeate (i.e. recovered reuse quality water) from Membranes, it was completely sterile. Secondly the same permeate, was kept for few hours & for a day. The microbiological contamination was absent for few hours. The contamination arose only after storage of the extracted water (i.e. permeate) for a day or so, for obvious reasons. This experiment was carried out at number of different sites & at different effluents. The results were same. The permeate was completely sterile immediately after emergence from membranes. Of course the sampling in such experiments must be done into sterile containers & fully observing the guidelines for such sampling.

In general, as regards membranes, the microbiological contamination gets cut off by using Ultrafiltration, Nanofiltration & Reverse Osmosis. However microfiltration membranes do not cut off the microbiological contamination. 

Hope this is useful for your purpose. The proof of the pudding is in eating. So we carried out actual experiments to verify the desired.