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SODIS Method of Purification

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1 SODIS Method of Purification on Sun Jan 22, 2012 10:29 am

PalmettoArcher

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Green Horn
I am curious to know if SODIS water purification will work using a 1 gallon ziploc bag rather than using PET bottles that we so often hear about in videos and forum discussions. I have experimented using a 55 gallon trash bag laid out flat on a slightly sloping ground to collect rain. I fold the corners of one end to make a funnel and collect rainwater in 1 gallon ziploc bags. It is amazing how guickly you can collect water using this method. I have found that even the lightest shower will fill a 1 gallon bag in about 15 minutes. To extend the viability of this method I would like to prove out the SODIS can be performed on water collected in ziploc bags.

One could technically present the argument that rainwater does not need purification; however, if time and resources permit, I would be more at peace knowing for certain my water is microbiologically clean before I consume it? I have experimented with various forms of chemical purification (Katadyn MicroPur, Iodine, etc.), and to the best of my knowledge, none of them are suited for long-term use. I am not sure about MIOX though. I cannot yet afford to purchase and test the mil-spec rated MSR unit, but it is on my list of soon-to-try and review items. In the interim, boiling, SODIS, and solar distillation seem to be the simplest, long term solutions. Please share your impressiona and experiences. Thanks brothers.

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2 Re: SODIS Method of Purification on Sun Jan 22, 2012 1:21 pm

alw357


Green Horn
Pardon my ignorance, but what is the SODIS method of purification?

I have been using a Katadyn Hiker Pro for a while now and I like and trust it. The only downside is the bulk. My next purchase in this area will be a Steripen. From What ive seen i like them. Especially the size.

Thanks Alan.

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3 Re: SODIS Method of Purification on Sun Jan 22, 2012 3:43 pm

PalmettoArcher

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Green Horn
SODIS stands for solar water disinfection. It is simple in theoy, using the ultraviolet and infrared light from the sun to destroy virus, bacteria, and parasites. The efficacy of the process can be impeded by using materials that absorb or otherwise block the transmission of the UV light spectrum. All translucent and transparent materials possess different optical characteristics. Almost all published information about the world health organization endorsed water purification method incorporates the use of PET (Polyethylene terephthalate) bottles. This particular type of plastic demonstrates ideal optical qualities making it especially suitable for SODIS. To the best of my current knowledge, PET is not BPA free, which means I don't want to drink from it. This fact brings me full circle to my current methods of water collection and temporary storage in ziploc bags. I am hoping they possess the right optical qualities to work with the SODIS method.

By the way alw357, you will be interested to know that your SteriPen works the same way as SODIS to disinfect the water, with the primary difference being that the SteriPen delivers a narrow band of UV light that the sun would deliver in several hours of exposure -- speeding up the process of making safe, potable drinking water.

I like the concept of the SteriPen and would love to have one someday. Keep us informed of your experiences with it.

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4 Re: SODIS Method of Purification on Sun Jan 22, 2012 6:54 pm

RangerXanatos

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Green Horn
Although I have heard of it in use,I wouldn't trust the sun as the only sort of UV disinfection. Say it rains and collects in a natural depression in a rock that is in full view of the sun. In theory, the sun should have destroyed any bacteria/viruses in that puddle of water, but I bet a streak plate would still grow something out of it. Besides, I've seen ponds in full sunlight that has nasty stuff growing in them.

Places that use UV light for sterilization such as biological hoods in labs and water treatment plants use a high output lights of UV that will create thymine-dimers in DNA, effectively killing the organism. But if that organism is covered by something, such as a type of sludge or clay, and the UV doesn't reach the organism then that organism is still liable to live and spread.

As a last resort, I would use the SODIS method only when the water is clear without any suspended or settled material.

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5 Re: SODIS Method of Purification on Wed Feb 08, 2012 1:01 am

MtnManJoe

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Tender Foot
It "should" work Great - not much depth of water allowing the UV-A to 'do it's thing' (Unless there is some UV-A Blocking in the plastic that the ZipLoc baggies are made of)
I am sure that that has been addressed somewhere in the literature.

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6 Re: SODIS Method of Purification on Wed Feb 08, 2012 9:38 am

untamed_wolf

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Green Horn
To my understanding, the SODIS method is used in situations where cheap, reliable and renewable long term water purification is necessary (ie. self reliance situations).

As long as there was sufficient exposure to UV light (time and intensity), it should do enough damage to microbes to make it safe.

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