The law that applies in your case is not EU law. Delta flying from Atlanta would be covered by US law so no, you have no comeback on the airline for this. You'll just have to live with the pittance.
It was a similar story in LAX, Delta were minimally helpful - even rebooking was a chore - and certainly no-body was supplying the queue with water (given the paucity of facilities in LAX Terminal 2 departures - no shops, vending machines or even water fountains -this was a real issue)