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Drinking water information and resources, contaminants, health effects, treatment methods

 Methods Of Emergency Water Treatment & Disinfection

 

Question from a visitor

What would you suggest for emergency preparedness?  Let's say if a person is mobile. What type of water purifier would you recommend?  What do you know about this MIOX® Purifier Pen http://www.miox.com/miox-solutions/MSR-MIOX-Purifier-Pen.aspx -
Thanks!

(1/1/14 update - MIOX is no longer manufacturing the pens - The product has been replaced by http://www.h2gopurifier.com//)
 


Answer:

It is an interesting gadget that basically produces chlorine bleach and other oxidants to disinfect the water. I was unable to locate any rigorous independent tests of the device, so I do not know how consistent the chlorine production is, but it seems to have good reviews. The results, I suspect, would be similar dropping in a chlorine tablet or adding iodine. Except for killing viruses this device would also, I believe, produce about the same results as a 0.2 micron ceramic water filter. Regardless, this is ONLY a disinfectant method which kills living organisms. It will not reduce the level of chemical contaminants, and actually adds chlorine, so its effectiveness in an emergency would depend on the contaminants in the water you were trying to treat.
http://www.h2gopurifier.com/

In answer to your question "What would I suggest for emergency preparedness", the answer depends on several factors: 
What type of emergencies are you preparing for; how mobile would you plan to be (do you mean backpacking on foot, or traveling by horse or car)
Would you plan to be constantly on the move or set up "camp" and stay in one location for a while
What would be the maximum acceptable weight of a treatment device?

The answer is also complicated by the fact that it would be virtually impossible to know what contaminants might be in a potential emergency water supply. Many harmful contaminants are not detectable by our senses at harmful levels. Another consideration is that some harmful contaminants (bacteria, viruses, cysts, etc.) can produce serious health effects in hours or days, while other harmful contaminants in typical concentrations (the disinfection byproducts for example) do not usually manifest harmful effects for decades, if at all. Other contaminants, lead, arsenic, etc. pose serious health hazards, but the concentration in most drinking water is relatively low, so the harmful effects build up relatively slowly over days, weeks, or years, and you might not even know your health is being compromised.

The most effective drinking water treatment methods, distillation and reverse osmosis (RO) followed by activated carbon filtration, are not optimal for emergency water treatment because they rely on energy sources for proper functioning which might not be available during an emergency, electricity for distillation, and a pressurized water source for reverse osmosis. Also, RO is not recommended for treating biologically contaminated water because imperfections in the membrane could allow pathogens into the "filtered" water stream.

Water treatment, particularly in an emergency, is nearly always a tradeoff - balancing potential contaminants in the water with the most effective treatment method available in a given circumstance.


It is important to realize the difference between drinking water disinfection and other  purification methods.
Disinfection is the removal or deactivation of biological organisms only.  Other contaminants that might be in the water may or might not be reduced.
Other purification methods may or may not disinfect water to some extent, but other contaminants are reduced depending on the treatment method.
Emergency treatment options:
Disinfection
Boiling, of course, will kill biological contaminants (viruses, bacteria, cysts), if a source of heat is available, but most other chemical contaminants (except volatile chemicals) are left in the water and may be concentrated.  According to the EPA - Below 1 mile boil vigorously for 1 minute, and at altitudes above one mile, boil for three minutes.
0.2 micron ceramic filter - if the filter media is intact, this will significantly reduce bacteria, cysts, and asbestos fibers but not viruses - as with boiling, most other dissolved chemical contaminants are left in the water.
Ultra filtration - special membrane filtration system with pores much smaller than ceramic filters but larger than reverse osmosis membranes. The high water pressure of RO is not required. If the membranes are intact, all biological contaminants as well as nearly all particulates (like asbestos) are significantly reduced. Like a ceramic filter, dissolved chemicals are not reduced. 
Addition of chlorine (tablets, halazone, liquid bleach, MSR Miox, etc.) or iodine - provides effective disinfection at the recommended doses, but does not reduce other contaminants and adds chlorine or iodine.  According to the EPA - to use household bleach, find the percentage of available chlorine on the label and use the information in the following tabulation as a guide.

Available Chlorine Drops per Quart of Clear Water

1%

10

4-6%

2

7-10%

1

(If strength is unknown, add ten drops per quart of water. Double amount of chlorine for cloudy or colored water or water that is extremely cold.).  The treated water should be mixed thoroughly and allowed to stand, preferably covered, for 30 minutes. The water should have a slight chlorine odor; if not, repeat the dosage and allow the water to stand for an additional 15 minutes.  This EPA site has instructions for other disinfection methods. 
Solar disinfection could be a last-ditch method of acquiring biologically safe water http://www.sodis.ch/index_EN
Filtration -- Advantages, water can be hand-pumped or siphoned through filters in the absence of electricity. 
Sediment filters are only effective for reducing the large particulates and clearing the water in preparation for other treatment methods.
Granular activated carbon (GAC) filtration (pitcher filters and many inexpensive cartridge filters) can be used to reduce some organic chemical contaminants from water.   Large pore size prevents effective use to remove biological contaminants (viruses, bacteria, and cysts). Can be used as a moderately effective second step to reduce chlorine or iodine from disinfection treatment.
Solid block activated carbon (SBAC) filtration (if the cartridge is not defective) can be used to reduce biological contaminants (cysts and many bacteria), depending on pore size - 0.5 micron or smaller is most effective.  SBAC filters will not reliably reduce viruses. Many organic compounds effectively reduced along with some inorganic compounds (lead, mercury, arsenic, asbestos) depending on pore size and manufacturer. Can be used as a very effective second step to reduce chlorine or iodine from disinfection treatment.

Effective carbon filtration systems tend to be relatively bulky (more so than the ceramic filters, for example) because enough activated carbon must be present to effectively reduce contaminants.

I have a high-quality under-counter SBAC filtration system in my home, and my emergency plan is to have tubing and a hand pump available so I can remove the filter from the cold water line, hook it up to the pump (siphoning would also work), and move water through it as needed. If I suspect biological contamination I could add the recommended dose of bleach, let it set, and pump it through the filter - removing the chlorine. This strategy would significantly reduce most contaminants except some heavy metals. The disadvantage is that the filter is relatively heavy and would not be an optimal solution for backpacking.

I hope this helps and best wishes.

Randy

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