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Typical biocides are reactive and toxic, exposing workers to a variety of hazards caused by the nature of these chemicals.
Because of purchase and operating economics, "wet" cooling towers are the technology of choice for commercial and industrial cooling systems. Water is the best material for both transfer of heat and evaporative cooling, but one drawback is that such use presents a biological control problem. 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 concentration, current trends that are being driven by freshwater shortages, increased water and sewer charges, and stricter environmental restrictions. 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
Current technology for biological control of cooling water depends upon various toxic, hazardous chemicals, such as chlorine, ozone, chlorine dioxide, dithiocarbamate, isothiazolin, hydantoin, and glutaraldehyde, that are commonly termed "biocides." While these biocides are often quite effective for biological control, their use represents a substantial health and safety concern. There are more than 300,000 cooling towers in the United States using an estimated 40 million pounds of such chemicals on an annual basis.
This toxic, hazardous chemical use is basically everywhere. 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, and retirement homes-basically, anywhere air conditioning or process cooling is needed. Smaller users represent a special worker safety concern because cooling water treatment, and application of biocides, is often the responsibility of generally untrained workers. Replacement of hazardous biocides by a non-hazardous technology will provide a substantial improvement in health and safety.
During biocide application, workers can be exposed to a variety of hazards caused by the reactive and toxic nature of these hazardous chemicals. Oxidizing biocides, commonly used as a gas such as...