The control of microbiological fouling in industrial cooling water for ‘open-recirculating’ and ‘once-through’ systems is important for reducing corrosion as well as increasing process efficiency and equipment longevity. Microbial biofilms insulate well and cause significant loss of heat transfer efficiency. In addition, they promote ‘under-deposit corrosion’ by multiple microbial induced corrosion (MIC) mechanisms. Furthermore, in ‘once-through’ seawater-cooled water systems where there is potential for colonization by various species, mussels create additional problems.

Historically, microbiological growth is controlled through a continuous chlorine feed, either as gaseous chlorine or sodium hypochlorite form. Gaseous chlorine has been largely eliminated because of safety concerns involving handling. Sodium hypochlorite is frequently used, but has significant problems involving storage, onsite generation and its usage in high concentrations leading to corrosion. In addition, recent environmental regulations limit the amount of these oxidants and their reaction by-products, such as tri-halomethanes, which can be discharged into waterways.

Chlorine dioxide an alternative that is a highly effective and safe microbiological control program. It is superior in offers a performance to all other chemistries with none of the environmental disadvantages. It is capable of maintaining excellent control of microbiological growth in cooling water systems and hence removing potential for MIC. This paper discusses how chlorine dioxide is generated, highlights its effectiveness against microbiological bacteria and presents the results of applications under various operating conditions, including those encountered in the Middle East.

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