Abstract
A bromo, nitropropanediol/isothiazolone blend (BNPD/ISO) was evaluated in an industrial cooling system to assess its performance and potential as an alternative to the oxidizing biocide program (gaseous chlorine) currently in use. Finding effective alternatives to gaseous chlorine is important because of safety and handling issues. Furthermore, chlorine has the associated problems of increasing cooling water corrosion rates, degradation of wood cooling structures, impaired efficacy at high pH, and sensitivity to organics and reducing agents in the water. The goals of this study were two-fold: First, to determine whether BNPD/ISO could be used as a chlorine alternative in an industrial system with equal or better performance at economically viable use levels; Second, to develop rapid, effective monitoring for nonoxidizing biocides in this system that would maximize useful application information without consuming large quantities of time and effort. The BNPD/ISO blend controlled the planktonic and sessile microbes in the cooling system. The solution to monitoring nonoxidizing biocides was determined to be ATP technology. ATP monitoring methodology was compared to standard microbiological field monitoring methods. ATP monitoring provided real-time data and was found to be an excellent monitor of nonoxidizing biocide efficacy. ATP methodology performed equally well in the presence of chlorine. Results of the effects of biocide on microbes were obtained within one hour after feeding the biocide. The total time needed to process the samples and obtain results was less than ten minutes. Field application data and results are discussed.
