The proliferation of microorganisms — bacteria, fungi and algae — presents a significant challenge in the maintenance and operation of process cooling water systems. Excessive accumulation of biofilm — and the activity of the microorganisms within — can lead to fouling, formation of mineral scales, amplification of pathogens (e.g., Legionella spp.) and microbiologically induced corrosion (MIC). If biofilm is not well controlled, the result can be loss of heat transfer, reduction in energy efficiency, downtime for cleaning, illness or death, corrosion-related failure and costly equipment repair or replacement. To minimize or prevent these issues, it is important to have a robust cooling water treatment program with a strong emphasis on biofilm control. A number of effective strategies exist for cooling water biofilm control. This article will primarily discuss the application of chlorine.
Oxidizing microbicides such as chlorine, bromine and chlorine dioxide make up the fundamental backbone of cooling water biofilm-control programs. This has always been the case, but more recent concerns for the control of pathogens, especially those causing Legionnaires’ disease, have placed increased emphasis on their use. The oxidizing microbicides are important in the control of biofilm and biofilm-related problems: Oxidizing microbicides not only kill microorganisms but also help to destroy the extracellular biofilm components. This is especially important in reducing the risk for Legionnaires’ disease.