Tap Water Nitrate Removal Systems

I saw a link to this page in one of todays advert popups and it interested me (made a change from mail order brides, and anyway, my last one escaped).
Its a resin based water treatment system to reduce Nitrates in domestic water supplies. The design is like a water softener in that it has resin chamber and a salt regeneration cycle.
http://www.eastmidlandswater.com/Details.asp?ProductID=2146

I cant imagine this being an exchange process, so I was wondering if anybody knew the principle? Is it a reactor or directly capturing the Nitrate?
I have seen fluid bed filters with polymer pellets for Nitrate/Phosphate reduction before, but I thought the media they use was consumed by the process, so maybe its the same but with a much larger tank that needs to be refilled periodically, but then why the salt regen cycle and would a polymer system be acceptable in a potable water system?
Anyhoo it made me wonder if the resin could be used in filters and the regeneration carried out manually like a bag of Purigen.