Silver as a water purification tablet?

torryquine

I recenty bought some water purification tablets for which the active ingredient is silver. I've never heared of this - always used iodine and will be taking this anyway, but it does leave a taste and is toxic. Would the silver ones be adequate for use with tap water, even in areas like northern Assam? We're obviously concious of not adding to the piles of discarded plastic bottles.

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wonderwomanusa

If silver would kill giardia or amoebas, we'd have been swallowing sixpences (or dimes) for many years. You might check for info on the CDC or WHO websites, but I would add a bottle of iodine from Boots to my bag ... and some flavored fizzy Vitamin C tablets.

vistet

I´ve heard claims of this effect - Teva claims a silver ion treatment prevents bacteria buildup, there have been a posting here about the supposedly miraculous qualities of sterling silver water flasks - but never seen any documentation.

Re iodine use , a quote from A Himalayan Medical Primer by Peter Hackett, MD :
"death = contact time x concentration of agent

Since "death" is a constant, doubling the contact time will allow half the amount of disinfecting agent to be used. For example , if sixteen drops of iodine solution are needed to disinfect a quart of water in thirty minutes, eight drops will disinfect in one hour, and only four drops are needed to disinfect the water in two hours
--

Note : if the water is cold (below 60 F ) or cloudy, double the dose or the contact time. If both cold and cloudy , double both the dose and the contact time. "

I´ve used the above model, at times combining this with a simple coffee filter first. All chemical methods will be more effective with prefiltering since the active substance can combine with with solid particles in the water.Silt in mountain streams can also be the cause of non-bacterial enteritis, which is a good reason to let the water settle before drinking.

Vitamin C is is nice to flavor the water (my favourite source is lime , when available) and should be added after desinfection is completed.

Nick-H

I was told many years ago by a metallurgist that silver is a natural antimicrobial.

Colloidal Silver was a commonly used antibiotic before the current generation eg penicillin etc was discovered.

It is now banned in USA due to the side effects of long-term use. It is deposited in the skin (which turns blue-grey) and in the eyes (which causes blindness).

It is available in UK shops such as Holland and Barrett.

As a water purifier I don't know, perhaps the concentrations are too low to cause ill effects, but I would be very wary of long-term use.

Google will reveal more!

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torryquine

[quote=wonderwomanusa]If silver would kill giardia or amoebas, we'd have been swallowing sixpences (or dimes) for many years.

Yup, that's my feeling too. I got Giardia in Nepal and don't want to repeat the rather protracted experience. I think the tablets we found in Boots are intended more for the "Spanish Tummy" varieties of waterborne parasites

It does seem to be a case of choosing one poison over another doesn't it? But I'll settle for the Iodine, it's handy as a disinfectant too.

Thanks for the advice all, I'd forgotten about the vitamin C tabs, good tip.

Cheers TQ

goangoangone

Boots sell a purifier containing silver



Micropur http://www.boots.com/shop/product_de...2&slmRefer=000

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Nick-H

Oh! I didn't realise that Micropur was silver-based

torryquine

Thanks, yes those are the ones. I hadn't noticed the bit about filtering and boiling in addition. Funny, but I thought that by doing that you didn't need additional purifiers. Is this naive of me?

Overall, I think I'll stick to Iodine when needed, but really, is filtering and boiling not enough?

goangoangone

I think if you've got the facility to boil then maybe you don't need the tabs.

vistet

This would be , literally, overkill. Boiling , when you have the time and fuel, takes care of everything.

There is a very good guide to water treatment here .

torryquine

Thank you all. That's a good site Vistet and confirms what I thought I knew...

Makes me wonder what use the Micropur really are though!

Cheers
TQ

mira4bai4

On the subject of boiling, there are a couple of variations here as altitude makes boiling occur at lower temperatures and it is the temp and the length of boiling time that ultimately kills the bugs etc. From my understanding it depended on the bugs in the water and their resistance to boiling temperatures, some bugs are happy to be boiled alive. It was recommended to me to double boil if boiling was the only option, boil, cool and boil again.

Why not carry a small portable 0.04 micron filter which allows water to be taken from streams or taps and filtered fit for drinking.

Baldy

other way round ... higher altitude means lower air pressure therefore higher boiling point (Boyle's law)

trvl_in

Well. I loathe the idea of taking iodine, but, seeing how well my hand washing and being careful system worked last time (didn't work), I am ready to be converted for my upcoming next go round.

Based on your advice cited above, it would seem that largish containers would be handy -- do 8 or 12 or 25 litres or whatever, using minimal iodine, and, given enough time, get all the health benefits with far less iodine. Good news indeed. Very good news.

I wonder -- what are the primary symptoms of an adverse reaction to iodine?

Nick-H

Baldy, I think you are wrong on this: Don't people say that you can't get a decent cup of tea up a mountain because the boiling water isn't hot enough?

Ahh... another thought. I know you are worng because of pressure cookers! The idea of a pressure cooker is that the boiling water/steam is at a higher temperature because of the higher pressure.

Boyles/charles' law is the only thing I remember from school physics! it refers to gases and says that p*v/t is always constant. It gives us the understanding of how a fridge works, but not of how water boils ....Duuuuh: I think (Phew! that was hard work )

Mira4bai4: With food cooling and reheating encourages bug growth; is it really a good idea to this with water?