Bruce -
YUP, same exact depth-filter media used by the electric power
industry, only nowadays they dont much use the presses for high KV
oils and instead use 'cartridges' 12" or 16" diameter with the same
depth filter material made up in 'cells' (looks like dinner plates
face to face) with upwards of 12 or 20 sq. ft. of surface area per
cartridge. Only problem is such specialized filters are not made in
small nor convenient sizes that could be used on small boats.... a
"cartridge housing" in ss would be in the neighborhood of $8k and a
'press' would be $25-30K (yikes) and thats for a 'small' set. When
such specialized filters are used on transformer, etc. oil, a single
pass through will get the water down to 40 part per million ... in a
single pass. The 'good' electric utilities still use tons of
these. ......... small world. What utility?

For small boats, noone makes better delivery line filters than Racor
Div of Parker-Hannefin - fixed resinated cellulose media; for recirc./
polishing the standard industrial PP 2.5"Ø anisotropic pore depth
filters are probably the best value you can find. As with most
maturing industries, there's a lot of crap and 'snake-oil' starting to
show up on the tech marketplace. :-)