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GAC - for Radon In Water Removal

By
Services for Real Estate Pros with CT Basement Systems Radon Inc.

Radon in Water

Granular Activated Carbon (GAC) & Aeration are the two most common mitigation strategies employed for radon in water removal.  While aeration is considered the best available technology (BAT) for waterborne radon mitigation; when applied judiciously, GAC is a viable treatment option. 

There are many different base materials from which activated carbon is made. The two most common are bituminous coal & coconut shells.  Granular carbon is activated by being "baked" at extremely high temperatures in an oxygen free environment.  The activation process creates an abundance of micropores which gives GAC it's enormous adsorptive capabilities.  Of the two types, coconut shell GAC has a greater amount of micropores.  In fact, one teaspoon of coconut shell carbon has the equivalent surface area of a football field.  At CT Basement, we use coconut shell GAC.  

GAC with pre & post clear big blue filters        GAC with neutralizer & softener

When selecting GAC for a radon in water problem, consideration should be given to several parameters.  Influent radon concentration, flow rate, proposed location of system, & size of home / potential useage demands, can all impact a GAC system's effectiveness...& ultimately, the welfare of the home's occupants.  Because radon collects on the GAC bed & doesn't go away until the bed is replaced, there are two important factors to keep in mind;

  #1) Service; a GAC system should be serviced at regular prescribed intervals to prevent the carbon bed from reaching "low level" radioactive waste status.  A system that is ignored & ultimately left in service for years on end, will very likely reach this level, regardless of influent radon concentration.  Furthermore, because GAC has the ability to remove a wide spectrum of contaminants, the carbon should be replaced regularly for hygienic reasons.  

 #2)Location; as radon is adsorbed on the GAC, it decays into decay products.  As these decay products disintigrate further, they begin to generate gamma ray emmissions.  Gammas have high penetrating power, therefore, sheet rock or basic masonry walls do not offer adequate shielding from exposure. A GAC system should not be located in the immediate vicinity of frequently occupied areas.  As an example; in a bedroom closet where the bed is positioned against the wall of the closet...this is not good!

The State of Ct recommends the use of aeration systems for radon in water concentrations exceeding 10,000pCi/l.  This is sound advice considering the aforementioned concerns.  Beware the contractor who recklessly proposes GAC for any given radon problem & doesn't take into consideration the impact of all associated factors.  Water treatment systems incorporating GAC as a part of a conditioning process should also be closely scrutinized.  Many of these systems have been in place for years without any thought given to radon & the potential impact it can have on the occupants. 

 

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