This is a follow up to my earlier posting about various water purification methods in the field. Please note that everyone has their own particular field water purification needs and one-size does not fit all.
In my case, I occasionally travel through urban and semi-rural areas in East and Southeast Asia, and not always the most developed areas. I stay at hotels and hostels and there is usually running water although it may be suspect. I eat at street-side restaurants that may not be that hygienic. The food is usually ok because it's been cooked but the water/lukewarm tea that gets served is suspect.
So my water needs are to to easily purify tap and street bought water (clean but maybe virus or parasite laden). As noted in my previous post, the obvious and best solution for this is UV-C water purification. Iodine / chlorinated tablets leave a bad taste and take too long and water filters are a pain to use.
Last year, I bought the UV Aquastar from Meridian Designs which is a UV-C lamp built into a nalgene water bottle cap. I took this on my Silk Road trip in China and it worked perfectly for the first 3 weeks. I could easily purify bottle and tap water by pouring it into the Nalgene bottle provided and sterilizing it in under a minute. I also loved how the bottle had a built-in white LED which turned it into a fantastic lantern. This saved my butt on several occasions.
The cons were that the cap contains the UV-C lamp assembly and it is hard to set down when you're taking a drink from the bottle. You pretty much have to carry it in your hand or you'll potentially reinfect the water when you screw it back on. Also, you could not easily purify small amounts of water -- for example when you're given a glass of water at a street restaurant.
NOTE: Photo courtesy of UV Aquastar.
The AquaStar unfortunately seems a bit fragile. In the third week of six weeks in western China, it broke when water entered the main electronics chamber through the lamp seal. The bottle isn't designed to handle pressure changes well and I think water ingressed into the elecronics when we crossed a mountain pass and the internal air pressure of the bottle was higher than the ambient air pressure, forcing the water into the electronics compartment through the lamp seal. To their credit, the manufacturer Meridian Designs immediately fixed it for free on my return to the United States. A couple of months later, the AquaStar broke again when the lamp cracked. And to their credit, Meridian Designs again fixed it for free. Kudos to their customer service department!
One other much more minor problem of the AquaStar was that it used CR123A lithium batteries. One set of two cells should last you about 60 liters or 16 gallons of weater. I think it's fine for hiking when you're only in the field for a few days, but it was a bit inconvenient in my six weeks in western China when I started to run out of CR123A batteries as my flashlights were also consuming then. It's possible to find CR123A batteries in the field, but they're much more expensive than if you can mail order them beforehand.
Would I recommend the UV AquaStar? Definitely for hikers and campers in the United States. It's what I carry when I go on short day hikes in Connecticut. It's just a bit bigger than a regular Nalgene and can be an emergency source of water -- or just a nice way to grab a drink from a beautiful mountain stream.
It's also great if you stay in one place for a longer period of time since you can use it for purifying tap water -- and in large quantities. You might want to get the AC adapter that AquaStar sells if you're going to do this.
The only thing I don't recommend the AquaStar for is for high-altitude over-road or airplane journeys. The cap design makes it hard to drink water out of the bottle if you're bouncing around in a cabin. Also, in my experience the lamp/electronic design does not handle air pressure changes well so you have to transport the bottle empty if you're gaining altitude, which defeats the purpose of having the lamp built into the bottle.
Steripen: This year, I bought the UV Steripen. It operates on the same UV-C principle as the Aquastar but is a different design. It uses four AA batteries and is designed to purify water that's already in its own vessel -- such as a glass, a bottle, or so forth. It's a bit bulky but I think it may be more useful in urban environments in not-yet-fully-developed nations. I'll give a field report in a couple of months when I've had more experience with it.
Commercially-available low pressure mercury-vapor lamps emit about 86% of their light at 254 nanometers (nm) ... UV light at these germicidal wavelengths causes adjacent thymine molecules on DNA to dimerize, if enough of these defects accumulate on a microorganism's DNA its replication is inhibited, thereby rendering it harmless (even though the organism may not be killed outright). Since microorganisms can be shielded from ultraviolet light in small cracks and other shaded areas, however, these lamps are used only as a supplement to other sterilization techniques.
UV radiation can be an effective viricide and bactericide. Disinfection using UV radiation was more commonly used in wastewater treatment applications but is finding increased usage in drinking water treatment.
Reviews of AquaStar and Steripen