Water is an increasingly valuable resource. Industry is one of the biggest users, consuming huge quantities for industrial purposes such as cooling. Typical examples are the cooling towers used in heavy manufacturing plants and those used for electrical power generation. Among the largest users per unit cost of product manufactured are the steel, chemical and pulp and paper industries. Industrial water consumption is a significant factor in production costs and has become important as part of the efforts to conserve water resources. In the past, much of the water used in industrial applications was lost into the atmosphere as steam. Today, the majority of industrial water is captured and continuously recycled. However, this brings new challenges as the water can easily become infested with unwanted and harmful microorganisms. These microbes need to be eliminated using biocides in order to avoid biologically induced corrosion, scale deposits and slime formation.