You can get a lot of filtration capacity by using a 0.45 micron depth filter to catch the major junk, with a 0.45 micron absolute filter (of smaller size) downstream of the depth filter to catch the little bit of tiny stuff that makes it through the depth filter. Depth filters take a lot longer to load up and are usually rated for 95-99% efficiency, whereas absolute filters can give you 99.9+% filtration efficient but load up quickly if you put the dirty wine directly to them. The more loaded a filter element gets, the greater the chance for 'punch through' (where high velocity flow in a small area can occur due to the high pressure drop across the major portion of the filter element).
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In all cases, you want to make sure the filter element does not have gaps around the edges-ends. Those gaps will allow stuff to get around the filter element. Many people use a permanently sealed cartridge absolute filter to minimize filter 'seating' problems. If I'm not using a permanently sealed 0.45 um absolute filter unit, I like to use the spear-point single open-ended with double o-ring filter types. There are less expensive double open-ended filter elements that use flat washers to seal both ends, but they don't seal as well. They USUALLY seal, but not always.
Commercial wineries typically use a diatomaceous earth pad filter system for rough filtering, and a 0.45 micron absolute filter just ahead of the bottling line to catch the odd fragments of yeast and ml bacteria.
Gene
