23-18: Overstabilization of Stabilized Bromine: Should this be a Significant Concern

The buildup of stabilizer in a cooling tower over time and the possibility of diminished biocidal efficacy is a concern, especially in cooling towers with high cycles of concentration.  There is certainly some precedent for this concern as chlorine in swimming pools can be overstabilized by cyanuric acid.  It has been speculated that having a certain level of stabilizer in a cooling tower would indicate the biocide is overstabilized.  However, the authors are unaware of any studies examining overstabilization in any detail.  In this paper, efficacy studies were done as a function of sulfamate levels to determine the effect on both planktonic organisms and biofilms.  Lastly, samples were taken from cooling towers treated with stabilized bromine so the measured sulfamate levels could be compared to the biocidal performance. In all of these cases, high levels of sulfamate (>100 ppm) did not significantly hinder the biocidal performance.  In the biofilm studies, sulfamate levels greater than 150 ppm were required to observe a degradation in biocide performance.