Pretty sure they have specific collection bins. Many keep them as a memento of the experience though.
Coldplay had similar wristbands when I saw them in Wembley last year and a big thing about their tour was sustainability. They definitely had collection bins for them at the exits, but I kept mine to satisfy my geeky curiosity.
Turns out it’s the same company that makes the wristbands for the Coldplay shows, so chances are it’s the exact same here