Clorine Water Treatmentgreenspun.com : LUSENET : TimeBomb 2000 (Y2000) : One Thread
Someone (I think Why2K) asked about clorine or pool chemicals to treat water. From way back in the Bear archives we dug this out. As usuall, the Bear cannot vouce for the accuracy of authenticity of the following information. We're consumers of this info just like you. We are NOT experts in this field. Anyway:
Chlorine: Chlorine is familiar to most Americans as it is used to treat virtually all municipal water systems in the United States. For a long time chlorine, in the form of Halazone tablets, was used to purify small batches of water for campers and military troops. Later questions emerged about the effectiveness of Halazone, and in 1989, Abbot labs pulled it off the market. If Halazone Tablets are encountered outside the US, the nominal shelf like is 6 months, and the dosage is 2 tabs per liter. Until recently, there was no chlorine product designed for wilderness/survival use available in the US.
Chlorine has a number of problem when used for field treatment of water. When chlorine reacts with organic material, it attaches itself to nitrogen containing compounds (ammonium ions and amino acids), leaving less free chlorine to continue disinfection. Carcinogenic trihalomethanes are also produced, though this is only a problem with long term exposure. Trihalomethanes can also be filtered out with a charcoal filter, though it is more efficient to use the same filter to remove organics before the water is chlorinated. Unless free chlorine is measured, disinfection can not be guaranteed with moderate doses of chlorine. One solution is superchlorination, the addition of far more chlorine than is needed. This must again be filtered through activated charcoal to remove the large amounts of chlorine, or hydrogen peroxide can be added to drive the chlorine off. Either way there is no residual chlorine left to prevent recontamination. This isn't a problem if the water is to be used at once.
Chlorine is sensitive to both the pH and temperature of the treated water, Temperature slows the reaction for any chemical treatment, but chlorine treatment is particularly susceptible to variations in the pH as at lower pHs, hypochlorous acid is formed, while at higher pHs, it will tend to dissociate into hydrogen and chlorite ions, which are less effective as a disinfectant. As a result, chlorine effectiveness drops off when the pH is greater than 8
Chlorine, like iodine, will not kill Cryptosporidia.
Methods of chlorine treatment: Bleach: Ordinary household bleach (such as Clorox) in the US contains 5.25% sodium hypochlorite (NaOCL) and can be used to purify water if it contains no other active ingredients, scents, or colorings. Bleach is far from an ideal source due to its bulkiness (only 5% active ingredient), and the instability over time of the chlorine content in bleach. Chlorine loss is farther increased by agitation or exposure to air. One source claims chlorine loss from a 5% solution at 10% over 6 months if stored at 70 deg. F. Nevertheless, this may be the only chemical means available to purify water, and it is far better than nothing. Normal dosage is 8 drops (.4 ml) per gallon. Allow the treated water to sit for 30 min., and if there isn't a slight chlorine smell, retreat. Note: USP standard medicine droppers are designed to dispense .045-.055 ml per drop. Use of other solvents or some chemicals can change this. The dropper can be calibrated against a graduated cylinder for greater accuracy.
Some small treatment plants in Africa produce their own sodium hypochlorite on site from the electrolysis of brine. Power demands range from 1.7 to 4 kWh per lb. of NaOCL. 2 to 3.5 lbs. of salt are needed for each pound of NaOCL. These units are fairly simple and are made in both the US and the UK. Another system, designed for China, where the suitable raw materials were mined or manufactured locally, used a reaction between salt, manganese dioxide, and sulfuric acid to produce chlorine gas. The gas was then allowed to react with slaked lime to produce a bleaching powder that could then be used to treat water. A heat source is required to speed the reaction up.
AquaCure: Designed for the South African military, these tablets contain chlorine and alum. The alum causes the suspended solids to flocculate and the chlorine adds 8 PPM chlorine. This is a great way to treat turbid water, though it will leave a lot of chlorine in clear water (The one tablet/L could be halved for clear water.)
The US distributor for Aqua Cure is: Safesport Manufacturing Box 11811 Denver, CO 80211 1 800 433 6506
Bleaching Powder (Chlorinated Lime) can also be purchased and used as a purification means if nothing else is available. Bleaching powder is 33-37% chlorine when produced, but losses its chlorine rapidly, particularly when exposed to air, light or moisture.
Calcium Hypochlorite: Also known as High Test Hypochlorite. Supplied in crystal form, it is nearly 70 % available chlorine. One product, the Sanitizer (formally the Sierra Water Purifier) uses these crystals to super chlorinate the water to insure pathogens were killed off, then hydrogen peroxide is added to drive off the residual chlorine. This is the most effective method of field chlorine treatment. The US military and most aid agencies also use HTH to treat their water, though a test kit, rather than superchlorination, is used to insure enough chlorine is added. This is preferable for large scale systems as the residual chlorine will prevent recontamination
Usually bulk water treatment plants first dilute to HTH to make a 1% working solution at the rate of 14g HTH per liter of water. While testing to determine exact chlorine needs are preferable, the solution can be used at the dose rate of 8 drops/gallon, or for larger quantities, 1 part of 1% solution to 10,000 parts clear water. Either of these doses will result in 1 PPM chlorine and may need to be increased if the water wasn't already filtered by other means.
When test kits are available, the WHO standard is a residual chlorine level of 0.2 to 0.5 mg/l after a 30 min. contact time. The may require as much as 5 mg/l of chlorine to be added to the raw water. --- That all for now
-- Greybear, pass the Pepto, please
- Got Filters?
-- Greybear (firstname.lastname@example.org), February 19, 1999
"The US military and most aid agencies also use HTH to treat their water, though a test kit, rather than superchlorination, is used to insure enough chlorine is added. This is preferable for large scale systems as the residual chlorine will prevent recontamination "
This means that if you're forced to draw water from National Guard or FEMA tanks and trucks that you'll have a strong taste of chlorine. Remember that taste well from as far back as Korea. Ugh..... Prefer my own water, thank you. My well draws deep, cold and sweet. Yep, time to get a filter.
-- De (email@example.com), February 19, 1999.
Thanks for posting such excellent information, Greybear! 'Twas indeed I who had questioned it. I'd been told years ago that drinking straight, unfiltered heavily-chlorinated pool water for any length of time was a big no-no, and could lead to renal failure. Will have to see if I can procure a few of those test kits.
-- Why2K? (firstname.lastname@example.org), February 19, 1999.
Good information on water.
The solar water puddle.
A little OT for this thread, but I'm posting it for the Newbies.
Bunch of stuff about "Things Solar", like ovens, food drying, etc.
-- sweetolebob (email@example.com), February 21, 1999.