The monomer 3-triethoxysilylpropyl-5,5dimethylhydantoin has been polymerized on the surfaces of sand particles to produce an adhered film that, upon chlorination with dilute sodium hypochlorite bleach, becomes biocidal. The biocidal efficacy of this coated sand has been demonstrated in a cartridge filter experiment against the bacterial pathogens Staphylococcus aureus and Escherichia coli. Complete inactivation was observed within 1 min of contact for the former bacterium and in the interval of 1-5 min for the latter. Upon a loss of biocidal activity due to the depletion of bound chlorine, the coated sand particles can be recharged by further exposure to dilute bleach. Synthetic methods and test data are presented. Potential uses of biocidal sand include disinfection and odor control in water treatment facilities and recirculating baths. (c) 2005 Wiley Periodicals, Inc.