Overview
Points out that hot and cold water services account for most identified cases of legionnaires' disease in the UK. Alternative strategies such as chlorine dioxide and ionisation have increased in popularity with the realisation that a temperature regime is not always achievable and in some cases not effective. Describes an experiment to directly compare the effectiveness of a temperature regime against chlorine dioxide. Uses a hot and cold water services test rig built to compare a temperature regime with hard water against alternative water treatments with hard and soft water. The plant and manner of operation were selected to represent a typical installation rather than best practice. Supplies and discusses the detailed results. Among the conclusions states that 1) low concentrations of chlorine dioxide were effective in controlling planktonic legionella bacteria and 2) for hot water circuits, the results suggest that the maintenance of hot water at 60degC flow and 50degC return does not provide complete protection from legionella surviving.