ABSTRACT
Effective microbial control in cooling systems is necessary to ensure system cleanliness and avoid fouling that degrades cooling system performance, promotes corrosion and favors growth of pathogens. However, controlling organisms optimally involves an understanding of the identity of the population of microbes in a system due to the varying susceptibilities of organisms to biocides. This is a challenging task with standard culturing techniques which only allow for a small fraction of the total population to be cultured and identified. In this study, 16s rDNA was employed to maximize the population identification of 40 different independent cooling tower samples. Many of the samples included pair planktonic and sessile samples from the same location. The analysis yielded over 282,000 sequences which corresponded to over 1,700 different taxa, demonstrating extensive diversity not only from remote locations but also within locations of close proximity. This shows that a wide variety of biocides are needed to address microbial populations.
INTRODUCTION
Background on WCT Microbial Issues Cooling processes use water as a heat sink, flowing over and through pipes and surfaces with many areas exposed to ambient conditions and environmental nutrients, not to mention nutrients stemming from industrial processes themselves. This creates an environment where microorganisms thrive and will take advantage of systems that are not maintained with proper chemical treatments.1 Microbiological activity causes a number of issues with some particular problem areas in a cooling tower, including fouling, corrosion, and through the spread of aerosolized pathogens. One of the major issues caused by organism accumulation is a reduction of heat exchanger efficiency due to the insulating characteristics of biofilm growth which also can restrict water flow or lead to full plugging of these tubes.1 Microbial influenced corrosion and pitting are more likely to occur in tubes and pipes containing biofilm due to the creation of chemical gradients and anaerobic conditions.2 Algal mats can form on open deck systems restricting water flow and in water lines creating clogs. Tower fill encompasses a lot of surface area, is open to ambient air and with drift water contacting contaminated surfaces, creates potential health concerns. Organisms will also contribute to biodeterioration of wooden components in a cooling tower. There are also potentially pathogenic organisms, which if captured in tower drift, may become aerosolized.
