A method for removing or preventing a microbial growth, biofilm, biomass and/or mineral deposit on a hard surface inside an SO2 scrubber is disclosed. In particular, biocide compositions may be dosed in pulse or continuously for the reduction and prevention of biofilms on the hard surfaces inside an SO2 scrubber. A biocide composition disclosed here uses one or more non-oxidizing biocides, especially a mixture of one or more quaternary ammonium compounds and one or more other biocides.
