This is my first post on BPL (on two threads)! I read the BPL store info on Aquamira drops, and also many other posts, as well as received a favorable recommendation from a store. However, I was taken aback by the fact that the product specifically does not make claims for efficacy and by the fact that REI does not carry it. So I have tried to do some independent investigation.
The following page is from the CDC (Center for Disease Control) and deals with the efficacy of various water purification methods. It is worth reading. http://www.cdc.gov/healthywater/drinking/travel/backcountry_water_treatment.html. It states that chlorine dioxide is very effective against bacteria, viruses and Giardia, but only somewhat effective against Cryptosporidium.
However this page does not provide any data to say how long a treatment by chlorine dioxide should take place. Relevant information can be found on the following EPA page: http://www.epa.gov//safewater/mdbp/pdf/alter/chapt_4.pdf
There are charts on that pdf that show the results for various pathogens at various concentration of chlorine dioxide at various temperatures and for various times. "CT" seems to mean concentration multiplied by time. To interpret the results from Aquamira, we need to know the concentration of chlorine dioxide. The 30 milliliter bottle of part A has a 2% chlorine dioxide composition, so that is about 0.6 ml. My research suggests that this solution may weigh just slightly more than water, so each bottle contains.6 gram or 600 milligrams of chlorine dioxide. The bottle is said to hold enough for treatment of (up to) 120 liters. However, I counted the drops in my Part A bottle: 690; that would only be enough for just under 100 liters if the recommended dose of 7 drops is used. Each dose calculates at 6 milligrams per liter (quart). So looking at the tables on the EPA page, it appears that the efficacy of chlorine doxide, even with very cold water, is excellent for everything except Cryptosporidium, where full effectiveness may require a several hour wait for cold water.
But if you look at the info on Katadyn chloride dioxide tablets at REI, it works relatively rapidly (15 or 30 minutes) for everything except cryptosporidium, which requires a 4 hour treatment for clear water. The packaging information states that it produces a solution of chloride dioxide of 4 ppm (parts per million), which would be approximately 4 milligrams per liter. Aquamira tablets have the same specification, i.e. 4 ppm chlorine dioxide and a 4 hour wait. Given that the liquid drops may be 50% stronger and that they can probably become active in water faster than can a solid tablet, the drops are likely to work faster. On the other hand, if cryptosporidium is a worry and the water is cold, a wait of 3 to 4 hours may be required. Since the Aquamira drop directions call for only a 15 or 30 minute wait period, this may be why they make no water treatment claims and have no EPA certification for water treatment.