Due to purchase and operating economics, "wet" cooling towers are the technology of choice for commercial and industrial cooling systems as water is the best material for both transfer of heat and evaporative cooling. One drawback is that such use presents a biological control problem as warm water, with dissolved and suspended solids present, is an excellent medium for growth of microorganisms. Growth of microorganisms in cooling water is further encouraged by use of reclaimed wastewaters as makeup and increased cooling tower cycles of Cooling Towers at a Public School concentration, current trends which are being driven by fresh water shortages, increased water and sewer charges, and stricter environmental regulation. The uncontrolled growth of microorganisms in cooling water causes severe problems related to increased risk of Legionnaires disease, plugging due to physical blockage of cooling water passages, accelerated corrosion under biological masses, and reduced heat exchanger efficiency due to biofouling of surfaces.
Present Practice – Health and Safety Current cooling water biological control technology depends upon various toxic, hazardous chemicals such as chlorine, ozone, chlorine dioxide, dithiocarbamate, isothiazolin, hydantoin, and glutaraldehyde; commonly termed “biocides". While these biocides are often quite effective, their use represents substantial environmental, health, and safety concerns as there are over 300,000 cooling towers in the United States using an estimated 40 million pounds of such chemicals on an annual basis. Use of toxic biocides is basically everywhere as cooling towers are found throughout our country; in neighborhoods, towns, and cities. In addition to typical industrial installations; cooling towers are commonly found at hospitals, hotels, grocery stores, office buildings, warehouses, apartment buildings, schools, colleges, and retirement homes; basically, anywhere air conditioning or process cooling is needed.