I’ve used 0.2um filters for removing powdery mildew spores from BHO. Done in ethanol prior to winterizing.
You could taste the difference
Went through a lot of these before figuring out where I could buy the membranes
http://www.eandkscientific.com/500ml-Corning-Vacuum-Filter-Systems.html
I could usually get several litres (multiple runs) through one filter, but would eventually crack the bottle as filtering slowed. The neat part was that the bottles would crack, and leak air in, but not liquid out.