Abstract
Chloromethyl-methylisothiazolone (CMIT/MIT) biocide is widely used for microbial control in a variety of industrial water treatment applications. It has been shown to be effective versus various types of bacteria, algae and fungi. Sulfate reducing bacteria (SRB) are of considerable interest for industrial water treatment due to their impact on biofouling and microbially influenced corrosion. This paper will provide results of planktonic and biofilm efficacy studies with CMIT/MIT biocide versus various strains of Desulfovibrio. Results showed that low levels of isothiazolone biocide (1-6 ppm active) provided control of SRB in liquid lab media and on surfaces in recirculating biofilm systems. Isothiazolone biocide is as highly effective versus SRB as it is against other slime forming bacteria, such as Pseudomonas species, as long as the biocide is stable in the system and sulfide levels are low. In sour systems (high sulfide), the biocide is degraded and its antimicrobial efficacy is reduced. The main pathway of degradation of CMIT/MIT by sulfide is presented. The importance of system cleanliness (biofilm accumulation) on biocide efficacy is discussed.
