Those prep pads sometimes contain a very mild detergent. Those which do will slightly foam or leave a white soapy look as they're used to prep. I have not been able to determine with any consistency which brands do or don't. Perhaps there are some surgeons or surgery tech. out there who can name a particular brand. HOWEVER: There are so many products actually intended for the purpose, and safe water is such an important part of the survival picture, why use a technique which is unproven. I wouldn't want to drink it. I do like the idea of multi-purpose items, but who needs diarrhea in a survival situation.<br>Read one of the wilderness medicine books in the ETS links for a pretty balanced picture of water purification approaches. I really want a "for sure" and not a "perhaps", myself.<br><br>