Marc,
Typically, to the extent I know, semiconductor industries use .05um filters
to remove particulates from DIW.  As to removing the particulates from
surfaces, techniques like "agitating" the water with megasonics and/or
using SC1 chemistries are used.

If your particulates are not removed by a .2um filter, I can only think of
partilulates being smaller than .2um, a bad filter or deforming particles
of some nature (however far fetched this may be).

Goodluck.
Jaideep

At 11:46 AM 5/20/99 -0700, Marc A. Unger wrote:
>
>Hi all -
>
>I'm looking for a way to remove particulates from water.  These particulates
>are not removed by a 0.2 um filter.  We use a few liters of water per day,
>and would prefer a higher-capacity filter (i.e. change filters every month,
>as opposed to every use).  I imagine the semiconductor industry
>already has something like this.  Could someone point me at a fix?
>
>-Marc Unger
>Applied Physics
>Caltech
>[email protected]
>
>