The biocidal efficacy of oxidizing (halohydantoin) and non-oxidizing (isothiazolones) biocide combinations against filamentous biofilms was compared to the efficacy of these biocidea alone under well defined Iaboratory conditions. Synergistic efficacy of halohydantoins and isothiazolones was indicated. The halohydantoin/ isothiazolones combination programs provided optimized cost performance with respect to biofilm control. The simultaneous addition of oxidizing and non-oxidizing biocides is the preferable mode of biocide treatment.
Both the research and industrial communities recognize the impact of biofilms in various aquatic industrial applications 13 Discussions on the strategies of biofilm control in various applications are Ieading towards the conclusion that complete kill of biofilm is nota realistic target. In practice, regrowth of biofilm calls that survive biocidal treatment may be slow but inevitable 4. Most of the current biocides were developed for planktonic microorganism control in the pre-biofilm time. Due to the fact that the search for new antimicrobial agents is becoming increasingly difficult, and requirements for bocide registrations are tightening, there is an industry trend to find ways of enhancing existing biocides. In practical terms, it means improving efficacy of established antimicrobial substances through optimization of their chemistry and, most of all, by creating new combinations. For years it has been known that many combinations of disinfectants work synergistically. Numerous combinations of active substances are well known, especially in a tent literature. Several examples of synergistic!6combinations of bocides are demonstrated in technical literature However, there is almost no quantitative data on the activity of combinations of biocides on biofilms. Most often, synergistic activities are demonstrated on planktonic microorganisms 7with conclusions transferred to biofilm a
Halohydantoins (oxidizing biocide) and isothiazolones (non-oxidizing biocide) are frequently used in cooling water applications. Both are used in different applications and their efficacy has been demonstrated many times in the laboratory and in the field 8-10,Combinations of these antimicrobial agents with many other biocides have been patented, There are several references on the synergy of isothiazolones with halogens ?2 However, these do not contain research data on synergistic effects of halohydantoins and isothiazolones on biofilms.
Previously published research demonstrated the efficacy of these biocides, when used separately, against biofilm a containing filamentous microorganisms in well defined laboratory conditions 13?4.As a natural continuation of this research, this paper presents a performance evaluation of halohydantoin / isothiazolones combination programs against microbial biofilms.
