The term used in the water treatment sector is "inactivation". Brent N is right, the UV disrupts the ability of the virus, bacteria or protozoan to replicate by damaging the DNA, and the Steripen uses the same technology. However, it is misleading in the article to characterize the water treatment process as "chemical free". Most treatment processes use free chlorine as a pretreatment to kill virus ( chlorine is ineffective against cryptosporidium and giardia) in order to reduce the size of the UV reactors and dose needed to meet EPA treatment requirements.
I like the Steripen too. It is simple to use and so far seems effective.
