I've got the same stuff in my pool. I added some DE to the filter. I didn't do it exactly right, but now that I've done the DE I don't seem to have as much sediment in the bottom of the pool. Here's the link to the thread where I was asking about what I did wrong when I added the DE.
http://www.poolforum.com/pf2/showthread.php?t=5376

It kind of explains the reason for the sediment. I think the sediment may be to fine and the sand filter won't catch it. That's my guess and that's why I added the DE.