Removal of Radon from Water Supplies

Abstract

Granular activated carbon (GAC) adsorption is extremely effective for the removal of radon from water supplies. A high removal efficiency is achieved through an adsorption/decay steady state that can result in near-background radon levels with currently available commercial GAC units. An adsorption/decay steady state analysis based upon secular equilibrium shows that the life of the GAC will be in terms of decades with respect to radon. A variety of GAC products were evaluated for radon removal and laboratory and field data are presented to document the steady state performance for water supplies ranging in concentration from 1,500–750,000 pCi/L. Because radon and its daughters build to steady state levels corresponding to the influent mass loading, the GAC bed becomes a source of low level gamma radiation. An empirical relationship is presented to estimate the maximum activity of the bed as a function of the influent radon concentration. This relation and other field measurements show that the low level activity of a GAC bed does not present a problem for the vast majority of high radon wells.