How it works: An ultraviolet light irradiates organisms in about 90 seconds. Usually all it requires is the press of a button.
Pros: The fastest solution available, and it doesn’t add chemicals to your drink.
Cons: Battery dependent, more fragile than other options, and it only cleans the water that the UV light can reach. A UV light for camping can treat about a liter at a time. And it won’t work in murky water.