CT Basement Systems Radon Blog by Matthew A. Bednarz V.P.

URANIUM IN WELL WATER

Posted by Matthew Bednarz on Fri, Oct, 06, 2017 @ 13:10 PM

uranium in well water

Uranium in well water has received much attention recently as a result of the State of CT recommending all private water well owners to test their water for uranium and arsenic http://1.usa.gov/WBDYmi (in addition to the common general water quality parameters).  Uranium (U) is naturally occurring in the earth's crust, and can dissolve into water if that water source is exposed to uranium bearing rock strata.  There is a significantly greater probability of elevated uranium in well water rather than in surface water supplies.

uranium concentrations[1]

High levels of uranium in well water may increase the risk of cancer and kidney damage.  The EPA has established 30 ppb as a maximum contaminant level (MCL) with a maximum contaminant level goal (MCLG) of zero.  The MCL was established on the basis of the heavy metal toxicity of uranium - not radioactivity.  It is this toxicity that is the primary health concern - not radioactivity when assessing health concerns over the ingestion of uranium in well water.  Uranium decreases the kidneys' ability to remove impurities from blood.  This condition is reversible if uranium consumption is eliminated.  However; it is the concern over radioactivity that must be contemplated when implementing a removal strategy. 

uranium

 Treatment systems that absorb or collect uranium with no backwash or regenerating capability will eventually reach a saturation point for radioactivity requiring special permitting for disposal of spent filter media.  Therefore, the most prudent approach for Point of Entry (POE) uranium in water removal is anion exchange.

While appearing quite similar to a water softener, (the outward appearance of both systems are identical) the anion resin functions differently from negatively charged cation (softening) resin.  Rather than removing positively charged ions out of the water, as is the case with water softener (cation) resin, anion resins have a positive charge and remove negatively charged ions (such as uranium and arsenic).  When an anion system regenerates, it uses the chloride portion of sodium chloride rather than the sodium portion that the cation resin does. 

The State of CT views anion exchange systems as a viable treatment option provided these systems discharge any water from the regeneration process into a dedicated sub surface drainage system (drywell).  Anion exchange is the most viable cost effective, whole house treatment solution for uranium in well water removal.

sub surface drainage 2017.jpg

A combination unit (referred to as a "mixed bed" softener) can also be installed if there is both hardness & uranium present in the same water supply.  This is an especially useful tool when floor space is at a premium.  The cation & anion resins are simply mixed within the same vessel.  This is a practical approach when applied to water with hardness levels up to 7 gpg.  

water softener cut away view resized 600

Reverse osmosis (RO) is the preferred point of use (POU) treatment to remove uranium in well water.  RO is a process where water is squeezed under pressure, through a semi - permeable membrane, filtering out the majority of dissolved solids, leaving just water that is free of dissolved solids for consumption. 

point of use reverse osmosis

The disadvantages to this option are; limited / slow production capacities, and the issue of having to draw water from a specific tap to get water that is treated...all other points of use in the home are not treated.  While installing separate POU RO systems can be a solution...it isn't practicle...and is oftentimes not feasible to accomplish.

Whole house reverse osmosis (point of entry POE) is an alternative to anion exchange and POU RO, but it can be cost prohibitive for many homeowners from both an install and maintenance perspective.  In order to have enough available water for demand, a large storage reservoir with repressurization is required.  Whole house reverse osmosis systems also "waste" large volumes of water to drain while processing treated water.

 

whole house reverse osmosis

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Topics: uranium in well water, water softener, reverse osmosis, mixed bed water softener, anion exchange