Ok so I just completed Dawnguard on the vampires side and I noticed that I cannot dump the 3 elder scrolls because they're quest items. It's really annoying because the scrolls are filling 60 pounds of inventory space and Urug gro-shub doesn't buy them anymore. Does someone know how to get rid of them?

There's an orc inside the library of The College in Winterhold that buys Elder Scrolls I believe, try him. He bought the Elder Scroll I got from the main questline.

Once either the Vampire or Dawnguard quest lines are finished, you can sell the Blood and Sun Elder Scrolls to the Moth Priest for a pretty chunk of change.

You get to keep the Dragon scroll for your MQ obligations.

I know you can get rid of two of them while talking to the moth priest. Did you beat the main quest? Also... If this doesn't work you could just make armor out of it... =p

Ah ok thanks, I'll be going to the moth priest then.

Quest items do not effect your weight despite the items listing a weight.

If you buy back the scroll from Urug gro-shub can you sell it back when you finish the Dawnguard DLC QL?

you can sell all 3 scrolls to the moth priest for 6000, unless you havent done the MQ yet then you need the dragon scroll