In an earlier post on Nuclear Radiation in Japan, I wondered whether we know how to treat Radioactive water.
I have found some information.
Certain rock types naturally contain radioactive elements referred to as NORM (Naturally Occurring Radioactive Materials). When a source of drinking water comes in contact with NORM-bearing rocks, radionuclides may accumulate in the water to levels of concern. The predominant radionuclides found in water include:
- radium (and its decay products)
- thorium (and its decay products)
- uranium (and its decay products)
As water is treated to remove impurities, radionuclides may collect and eventually build up in filters, tanks, and pipes at treatment plants. The small amounts of NORM present in the source water may concentrate in sediment or sludges. Because the NORM is concentrated due to human activity, it is classified as TENORM (Technologically Enhanced Radioactive Material). Most of this waste is disposed in landfills and lagoons, or is applied to agricultural fields.
Most drinking water treatment sludges are thought to contain radium (Ra-226) levels comparable to typical concentrations in soils. However, some water supply systems, primarily those relying on groundwater sources, may generate sludge with much higher Ra-226 levels. Furthermore, some water treatment systems are more effective than others in removing naturally-occurring radionuclides from the water.
The table below lists the current radionuclide standards for drinking water.
http://www.epa.gov/rpdweb00/tenorm/drinking-water.html
a) Radioactive contamination of drinking water in Japan at this point in time can come about in only two ways:
1) The source is actual surface water like lakes or rivers, possibly filtrated through river banks and thus came into contact with e.g. radioactive rain and/or dust. The Netherlands rely almost totally on water drawn from the Rhine and fed into the drinking water supply after conditioning.
2) The water may have been contaminated after production (e.g. in open cisterns/basins), which in effect is similar to bullet a1).
In all other cases it springs from groundwater (wells) and has often been concealed for years before being extracted again. As limnologists would say “groundwater” has an elephant’s memory, i.e. if you drop a can of used oil in a forest it may take ten years until you become aware of oil traces in your drinking water. This means that on one hand ground water wells should as a rule not yet show contamination from rain fall so shortly after a nuclear accident and on the other hand that when it appears further “down the road” all short-lived contamination should have decayed. This is by no means meant to downplay the issue.
So far I would have thought it unlikely to already find radioactive contamination in water that does not come from surface water or bank filtrate. If it should be true it would be alarming.
Now though, let’s assume it were true as authorities would rather hush up things than exaggerate them, thus let’s take some degree of water contamination for granted.
b) How can you reprocess radioactively contaminated (drinking) water so that it is (relatively) safe to use?
1) It is in the form of radioactive hydrogen (called tritium, three times as heavy as normal hydrogen and emitting very weak beta rays, i.e. electrons, which, however, can damage yourgenome and cause cancer etc. when swallowed). When tritium has been released to the environment it will be incorporated in “heavy” water molecules. However, these are chemically indistinct from normal water, hence you cannot chemically separate radioactive water from normal water. You will have to live with tritium in your water and air (vapour) until it has decayed. With a half-life of approx. 12 years it will be down to one thousandth in about 120 years … All you can do (in theory) is move to another location where the tritium from “your” power plant has not yet reached (eventually the tritium will be evenly dispersed world-wide by wind and wave, however, then also the dosage of radiation will diminish reciprocally with its dilution). Or you “import” clean water (and add a pressurised air cylinder from a clean pristine source for good measure).
And don’t forget: once you’ve moved to another place there might be yet another malfunctioning nuclear power station around the corner – from the frypan into the fire … Help close down all nuclear power stations and so-called reprocessing plants!
2) The water could contain gases, esp. radioactive noble gases (like neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn)) Rather unlikely but for the sake of completeness we will mention them here. These can be driven out from the water by heating it to boiling temperature as hot liquids dissolve less gases than cold ones (with solid solubles, e.g. salts, it is vice versa with the rare exception of kitchen salt –sodium chloride- which hardly changes in solubility from almost zero to 100 degrees centigrade).
3) The main contaminants by far should be soluble solids, e.g. metal salts of e.g. radioactive caesium, rubidium etc. These can not be filtered e.g. by charcoal or any ceramic or paper filter with whatever fine pore structure since they are dissolved! You can only either try to demineralise that water (e.g. by reverse osmosis) or purify it by distillation thus leaving the radioactive solids behind (the condensed water in the lids of your pots consists of such distilled water droplets). A third potential method would be chemical precipitation. However, in order to know which chemical to use to precipitate the contaminant(s) with, you’d first have to analyse the water components. And in all probability the traces would be too small for normal analysis and if the salt etc. was determined then you might find there is noprecipitant to go with it or it may have adverse side effects, e.g. be poisonous. So de-mineralisation or distillation it is.
While activated charcoal does by virtue of adsorption delay the passage even of solved saltsall these filtration methods are only really designed for capturing suspended matter. But what has been bank filtrated or springs from ground water wells is not a suspension, or at least no water utility would dare inject murky water into its system!!!
See the German version here, if you are more comfortable with German:
http://www.dasgelbeforum.de.org/forum_entry.php?id=209608
Can you still use contaminated water for the following purposes (keep in mind, it is always a matter of how contaminated it all is!):
> – cleaning a garden path for example,
Yes, but may I suggest: only if the path would be less contaminated than before. But before you breathe contaminated dust from a contaminated path by all means use contaminated water to keep it in place! This is what is already done at Fukushima – they spray water not only for cooling purposes but also to keep the contaminated dust or radioactice debris wet and in place!
> – personal hygiene,
Rather not! You would also absorb some contaminants through your skin, however small. However, if you need to decontaminate yourself from a greater dose than what is in your water, do wash it all down and reduce your exposure! Again – “contaminated” water may be heavily or only negligibly contaminated – use your best judgment! We are talking dangerously contaminated here! The situation in your region may not yet be so dire – so please compare to normal radiation levels from the past – traces of radioactivity may not always be dangerous, but are likely to rise with ongoing leaks and further rainfall adding to ground water supplies from contaminated sources above ground:
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