No worries Patricia - maybe just acknowledging the forum in your project, whether you use anything from here on not, would be good.
There are a few unknowns involved as I see it:
Sample material size and therefore what filter type.
Flow rate of pump required.
Just how to oil-compensate a suitable pump.
I would be going for the largest bilge pump flow as you can afford. 2000 GPH sounds better than 500. Note the current draw though - make sure power on the ROV is up to it. Not having had anything to do with bilge pumps other than in their designed application myself,
maybe others on the forum have tried pressure-compensating them or know of ways to do it. Any ideas guys?? Something like a "shop-vac", but rated to 1000'.
Refer attached conceptual sketch of what I was describing earlier. Once again, get someone suitably qualified to do any mods to the pump, cutting holes in the drum etc if you decide to go this way.
You've probably considered some kind of miniature trawl net the ROV could drag around, or are there too many obstacles on the bottom? Would be much simpler if it worked
http://www.scotland.gov.uk/Resource/Img ... 092231.jpg
Ross