It won't help you much on the trail, but Chlorine bleach is still an effective water treatment method and should be available most everywhere. It would be a good idea to know how much bleach to add to water to purify it before you go. 12% industrial strength bleach has about 1 Lb of free Chlorine per gallon, 6% household bleach about 1/2 Lb of free chlorine per gallon. To know how much is needed, you need to know the Chlorine demand of the water to be treated. There are rules of thumb for almost everything, but I'm not current on this. It shouldn't be too hard to google this and come up with some reasonable treatment rate. One gallon of 6% bleach will generate a 1 PPM in 500,000 Lb of water or about 60,000 gallons. To get 1 PPM in one gallon would require about 1/16 of one Milliliter of 6% bleach. Normal Chlorine demand should be 5 - 6 PPM, so around 3/8 mL. At 20 drops per mL, around 7 - 8 Drops of 6% bleach per quart of untreated water. Normal minimum contact time is 20 minutes. A 1 Part per million concentration of Chlorine bleach has a bleachy odor. This is something that you can try at home to get some idea of what it is like in the field. If your water has had 20 - 30 minutes of contact time and it still smells bleachy, it's probably safe to drink. Excess bleach isn't good for you, but in the PPM range, it's less harmful than pathogenic bacteria. In small private water supplies, we have looked for a Free Chlorine residual of no less than 0.2 mg/L in the finished water product. This level would be well below the taste and odor thresholds for normal human beings. The military has probably developed guidelines for treating questionable water. They can't afford to have a bunch of troops out of action because of bad water. Most of the Chlorine Dioxide treatments require 4 hours of contact. This is primarily because the Chlorine Dioxide has to be generated before it can kill the pathogens. Bleach may not be as effective as Chlorine Dioxide, but it's active the moment that you mix it with the water to be treated. In a 1 to 10% solution, it's an effective surface disinfectant that can be used to avoid cross contamination. The 1 to 10% solutions are the actual dilution of household bleach, not the concentration of Sodium Hypochlorite in water. The washrags that your server wiped your restaurant table down with probably were a 1% bleach solution. Bleach is an effective disinfectant and is commonly available, a fact that should not be overlooked.

https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water

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