Katadyn states that some of its water filters (such as its Gravidyn Drip Water Filter) are able to filter radioactive particles from water. I assume these water filters only remove some (the bigger) particles.

The reason I bring up the Gravidyn, is that I had heard that is what some of the relief agencies used (such as the Red Cross) during last year's nuclear disaster in Japan.

I've been poking around a little in the literature and found that there's a considerable amount of diverging/conflicting views on this.

Questions:

In regard to filtering water that is contaminated with radiation, would a water filter such as the Gravidyn be of any use? Are there any studies that quantify the amount of improvement such a filter can make?

Are there any water filters (that are being sold at this time) that are dedicated specifically to removing radiation from water -- to the end that radioactive water could be made safe enough to drink?

I'm far from an expert, but I think it is important to remember that it is not the radiation itself that contaminates the water, but physical particles and possibly gases that are radioactive that contaminate the water. Remove them, and you remove the radioactivity.

The Gravidyn is spected to remove particles greater than 0.2 (0.0002mm) microns. Thus, if the radioactive particles are greater than this size, they get trapped. If smaller, they don't. I don't know about gases, but the activated charcoal may trap some also.

So in principle, any filter will catch some particles, but the radioactivity of the particle has nothing to do with it. It is what the filter is designed to catch in terms of physical size of particles and types of gases. I assume almost any filter will help to some extent. When in doubt, use the best filter available.

The real concern to me is that if the filter is catching radioactive particles, then it will become increasingly radioactive itself, and eventually become a potential hazard itself.

I don't think actual water itself (pure H2O) is easily made radioactive--- its what is in it that is the problem.

A good question and one that may not have an exact answer.

My understanding is that radioactive fallout, such as from a nuke explosion is relatively large and most of it can be filtered out without too much trouble.

I suspect the same is true of this kind of radioactive debris.

I suspect there is some that is going to get through no matter how good your filter is. Whether that is enough to harm you in any significant way is the real question.

Even an RO won't remove radioactive dissolved gasses.

The actual solution to this problem, if it really is a problem, and not just something someone dreamed up to worry themselves about, is to check the filtered water with a portable radiation detector before drinking it.

Keep in mind there is likely to be a fair amount of radioactive particles in the air in such an area, and that is probably more of a health hazard than the radioactive particles in the water.

Radioactive particles can only be filtered based on the fact they are particles rather than that they are radioactive.

The issue then becomes one of filter effectiveness against whatever the particle size is. (I wouldn't know particle sizes for such an accident)

The concern for the filter becoming radioactive is correct though the filter could only become a hazard to handling if it were filtering particles giving off gamma. Alpha and beta radiation wouldn't escape the filter body though the filter should be disposed of as radioactive waste when done.

An alternative method to create safe water would be to distill it. All particles would be left behind in the boiler.

Just be sure the revenooers know what you're boiling :-)

In regard to distillation as an alternative to a filter, below are excepts from other discussions about whether or not distillation works. Each excerpt is from a different commenter. I have no idea as to the level of expertise of any of these commenters and please assume they're taken out of context to some extent. Grady

". . . distillation . . . will only serve to concentrate the problem within the containment or filter itself." [Grady's observation: Maybe containment would not be a bad alternative if you have enough spare filters and a dependable Geiger Counter.]

" . . . not sure that distilling the water will work either.. I have heard that the steam (that's what distilled water is) from the plant was radioactive.. meaning that the isotopes were lighter than water and distilled into the steam as well.."

" . . . filtering through earth removes essentially all of the fallout particles and more of the dissolved radioactive material than does boiling-water distillation, a generally impractical purification method that does not eliminate dangerous radioactive iodine . . ."

" . . . trying to use an improper closed distillation rig will send over not just water, but organics and dissolved gases which need other steps to get rid of. Home distillation kit wouldn't work well to get rid of I or other gas phase-elements . . . "

"One of the problems with distilling is that iodine has a low boiling point - it turns into a gas at 184 Celsius. The little home distillers use high pressure for efficiency and if they are using over ~140 psi they will be vaporizing the radioactive iodine along with the water."

"A low pressure distiller like the type used for distilling alcohol won't boil off the iodine."

distillation is ". . . far more complex than anything simple. distillation has to be designed to gas off organics and iodine separate form water. otherwise all it leans out is solid particulate/mineral . . ."

". . . you keep distilling water down and that distiller is going to get very radioactive itself. Do you want to touch and use it then? Better to go with DISPOSABLE filter setups . . . production models or home made."

"By drinking distilled water you will actually dilute and cleanse out many accumulated impurities in your body as well."

". . . distilling would be your best bet..."

REBUTTAL to the above excerpt: "The steam coming off those reactors is filled with contamination. Comprende yet? The pressure and heat energy propels the radiation. Comprende yet?"

Second REBUTTAL: " . . . You cannot distill radiation out of water. The reactors are distilling water and radiation into the air. Stop giving bad advice. Someone may use it."

"Does a water filter remove radiation from water?
Particulate contaminants, yes; depending on the micronic efficiency of the filter. Will not restore irradiated water. Need to distill the water to do that, and then you have the radiation contaminants to dispose of, deal with....".

"I'm sorry to say that distills will not remove radiation from the water itself. I have a company that sells them and would love it if they did..."

FYI - photos of stills sold commercially: http://homedistiller.org/photos-sold.htmhttp://homedistiller.org/photos-sold.htm

The steam from the reactors is NOT distilled water. It is boiling water with entrained corrosion products, corrosion control chemicals, various fission product particles and gases of all kinds (both radioactive and not).

So maybe one of the first questions is - what is your water source? Reactor plant coolant/steam? Rainwater? Sea water? What? Makes a huge difference.

Distillation will indeed concentrate the particles in the boiler. As long as you don't drink from it and don't concentrate so much radioactivity that you can't approach it, you ought to be able to drink the distillate.

Or not. This is the internet. Everyone knows an answer of some kind.


(I'm speaking as a nuclear trained submarine operator relying on some common sense physics. We were never trained to treat radioactive water to make it potable. But if I were in the situation, I'd go with distillation. )

Unimogbert - thank you for you excellent well thought out comments.

I'm looking for anything that would be better than nothing.

I think with meters someone could learn to safely handle the cleaning of a boiler and the proper storage & disposal of filters (even emulating compliance with regulatory standards).

I have two water source scenarios in-mind (at this point it is only academic):

First scenario: stationary in a small house in small town with city water --- whose source is an underground aquifer; a closed system. Potential backup sources would include ditches in or about town and roof water.

Second scenario: (to be avoided if at all possible) is having to get water from bayous, abandoned rice irrigation canals or gullies.

As to the second scenario, I've been looking around for "packaged" non-electric water distillers - hardly any out there but here is one: http://www.waterwise.com/productcart/pc/1600.asp

If it is a long term event, I think the biggest issue would be having an adequate supply of fuel so as to run the boiler for the duration.

I haven't seen anyone yet suggest the possibility of filtering the contaminated water first, for instance with Katadyn's Ceradyn (with 0.2 micron elements) and then (also) distilling it. This, of course, would only be an option at a stationary location.

Sawyer makes a .02 micron filter (Adventure Safety Products) that would get you 10x smaller with particulate size

Underground aquifer would be safest and not even need any treatment. If you've got that then there's little reason to work on this angle of prep unless you have to travel.

Other water sources, if given time for particles to settle, would likely be only lightly contaminated. Collecting water from the upper layers of the water body and letting it settle further in containers before boiling or filtering would help.

I suspect there is lots of useful advice in the old Civil Defense texts about surviving radioactive fallout from bombs. The idea there was to stay underground for 2 weeks while the radioactivity decays. I haven't read much further than that.

But it needs to be said that bomb fallout is probably a different distribution of radionuclides than that from a damaged reactor core.

Don't mean to send this thread off-topic, but since you're concerned about radioactive particles in the water, just wanted to point out that eating contaminated food is generally considered the primary route that radioactive particles get into our bodies. This was the experience after Chernobyl. Plants, or animals that eat plants, take up the radioactive isotopes and concentrate them, similar to how mercury becomes concentrated in sea animals as you go up the food chain.

If you really want to be prepared for living with something like Fukushima, then a safe stock of food is certainly a must. And if you check natural or alternative health websites, there are things you can consume that are claimed to bind up the radioactive particles, like certain kinds of edible clays, zeolite powder, certain sea products, etc.