CURRENT MICROBIOLOGICAL CONTROL PROGRAMS IN COOLING TOWER WATER SYSTEMS MAY NOT BE CONTROLLING LEGIONELLA BACTERIA

摘要

Due to the recent outbreaks of Legionnaire's Disease such as in New York City, it was decided to investigate how and why this could have occurred by cooling tower water systems that were chemically treated. Cooling tower water systems are normally treated by the traditional method of applying microbicides and often monitored with traditional total bacteria monitoring methods. This has prompted a detailed review of the traditional microbiological treatment applications in numerous cooling tower water systems in all types of industries systems to see if there are any reasons that Legionella bacteria could still be present. The study showed that traditional microbiological control techniques might be incorrect and misleading in controlling Legionella bacteria due to the way the microbicides are being applied. Examples are identified that was found in numerous cooling tower water systems and in various industries. They show some very interesting and revealing information in how the microbiocides are applied that may not be an indication of effective control of Legionella bacteria. It also shows that the traditional monitoring levels of total bacteria levels that have indicated good microbiological control as reported by culture or "dip" slides may be incorrect and that the guidelines by CTI and others which indicate that 10~4 or less implies good microbiological control is incorrect. This study and the results suggest new applications and monitoring methods should be adopted.