Peroxide is wonderful. There are just so many things it can be used for. One use that comes to mind is that is sanitizes produce. When I fix a salad, I put everything in a large bowl, fill with water, add about a cap full of peroxide, try to keep everything submerged and let it all soak for about 20 minutes. Now, the salad has been disinfected.
Doing the same soak will bring wilted lettuce back to it's original crisp state. If your lettuce is still good but no longer crisp, give it a peroxide soak and see if you can rejuvenate your greens.