Hawaii water catchment; efficacy of carbon filtration for radionuclides?
Perhaps this has been discussed before; please accept my apology
in advance if this subject has already been covered.
Preface: I live in Hawaii, we "catch" our water from the roof of our home.
50,000 people in Hawaii receive their domestic water from rain.
Due to the extended crisis at Fukushima NPP, I am concerned about our water quality with regards to nuclear fallout/rainout. Using a Geiger-counter with a pancake-style probe and graphing software, I was able to measure a 50% increase in combined alpha/beta/gamma emissions from our carbon water filter element, as compared against baseline reading taken before the accident. The filter was replaced immediately after the Japan tsunami, and was in service for 30 days before replacement and subsequent radiologic survey.
I would like clarification on what my filter options are to reduce radioactive contaminates from our domestic rainwater catchment supply.
Specifically, would activated carbon provide an effective method for meaningful reduction for dissolved radioactive contamination in drinking water? Obviously, our carbon filter is capturing some of the contamination, but at what percentage I can only guess...? I would prefer to avoid solutions that require reverse-osmosis, as these are expensive to operate and waste a considerable sum of water as discharged to waste. I am considering additional filtration stages utilizing some formation of cation-exchange-resins.
hamlet_jones ~at~ yahoo ~dot~ com
active carbon and water purification
Hi Hamlet,
The efficiency of removal of radionuclides from rain water with active carbon depends on many things: the grain and pore size of the carbon grains, the pH of the water and of course the specific radionuclide. It is not to be expected, that carbon as such will be very efficient for Cs isotopes in solution, my guess is 10 - 30%. A carbon cartridge however also acts as a particle filter. Mosses, lichens and certain leaves do have some tendency to accumulate Cs. If those materials are present on roofs and come from the roof with the rain water, they will be filtered by the carbon cartridge. The same is true for radioactive inorganic particles of greater size (let us say 100 micrometer). As such, a cartridge helps. If radionuclides are present bound to organic materials in the rain water (either leached from the roof or not), there is also an improved probability that a carbon filter will adsorb them. Such element-ligand compounds are likely to precipitate on the high specific area that is so characteristic for active carbon. This could be the case for Co-60, Zn-65, Fe-55 etc. The problem is, that especially the radionuclides causing the biggest problem at this moment, Cs-134 and Cs-137 are not likely to be bound to organic ligands.
The purification efficiency of carbon can be improved by adding artificial ligands to the water, usually dithio carbamate type of compounds. I would strongly suggest to stay away from those compounds, as they are toxic for humans.
I do not think that ion exchangers will work. They usually are effcient at much lower pH values than the natural pH of rain water (5 or 6 in Hawaii?). It means you will have to add acid. I don't think that would be a good idea.
If you are convinced, that radionuclides occur in solution in your rain water, you might consider the use of chelating materials, such as Chelex-100. This material works at natural pH values of rain, has sufficient capacity and is basically a natural plastic. It will not trap Cs-137 or Sr-90, but Co-60, U-235/238, Pu-239, Zn-65 and basically all cations of oxidation state greater than +2 will be removed from water. I would strongly suggest not to use the filtered water for intake, but bathing, showering, dish washing etc. could in my view be done save. You should realize that you end up with a sort of demineralized water; this has disadvantages.
I do hope it helps you a liitle. If you need more info, please sent an Email.
Kind greetings,
Joost
Try multi pure ro 750
I feel bad for people That caught rainwater Drank it bathed in it cooked with it when it contained all these isotopes from Japan.how much of Hawaii population catches water? did u take any rain samples in march April or did the EPA in Hawaii take precipitation samples to sound the all clear no danger ?I personally rely on river water and experienced black sooty substance in toilet bowl for three months never before have I had this happen.any how I am in a similar spot as those who collected tainted rain.I upgraded my carbon block to include a reverse osmosis filter this system can be zero waste/ no water down drain just buy the recommended pump ect.there's lots of info on this forum about filtering of radiation just use the search .
http://www.multipureco.com/mpro.htm