Recirculating water transfer thermal energy from the building or industrial process to the atmosphere. Atmosphere air blown through the cooling tower carries away the heat. Environmental problems arise when water escapes from the system in the form of droplets. Such water droplets carry with them various chemicals that are used in the system. Some of these chemicals are environmentally harmful.
Hexavalent chromium is the one that is of the most concern and warrants immediate attention.
The trouble is, hexavalent chromium is a suspected carcinogen, and is highly toxic. This prohibition is expect to reduce the risk of cancer cases due to cooling tower emissions to virtually zero. Additionally, elimination of hexavalent chromium-based treatment chemicals will eliminate the amount of hazardous and toxic wastes discarded through blowdown. Most cooling towers are designed with recirculating water systems to conserve water resources and reduce costs of purchasing water. Cooling towers generally use open recirculating systems, although some employ closed systems.