The biocidal efficacy of halogenated hydantoins against
laboratory-prepared biofilms was compared to the free halogen donors NaOCl and NaOBr. Higher biocide concentrations were required to control a filamentous biofilm than to control free floating planktonic bacteria. Control of a biocide-resistant S. natans biofilm was best obtained with a repeated slug+3 hour continuous treatment procedure or with conventional continuous biocide treatment. A bromine,
methylethylhydantoin-containing oxidizing biocide (BrMEH) was found to be more efficecious than either free chlorine or free bromine in controlling filamentous biofilms. Previous studies indicating the inabilily of free chlorine to penetrate biofilms were supported as the combination of free and combined halogen was demonstrated to be more effective than
free chlorine or bromine alone against attached bacteria.
Keywords: halohydantoins, halogens, control, biofilms, planktonic microorganisms, filamentous bacteria, Sphaerotilus natans, heat tranafer resistance, dissolved oxygen