Influence of temperature, chlorine residual and heavy metals on the presence of [i]Legionella pneumophila[/i] in hot water distribution systems

Anita Rakić 1,  
Jelena Perić 2,  
Public Health Institute, Split, Croatia
Faculty of Chemistry and Technology, University of Split, Split, Croatia
Division of Industrial Ecology, Faculty of Chemical Engineering and Technology, University of Zagreb, Zagreb, Croatia
Ann Agric Environ Med 2012;19(3):431–436
The microbiological colonisation of buildings and man-made structures often occurs on the walls of plumbing systems; therefore, monitoring of opportunistic pathogens such as [i]Legionella pneumophila[/i] ([i]L. pneumophila[/i]), both in water distribution mains and in consumers’ plumbing systems, is an important issue according to the international and national guidelines that regulate the quality of drinking water. This paper investigates the presence of [i]L. pneumophila[/i] in the Dalmatian County of Croatia and the relationship between [i]L. pneumophila[/i] presence and heavy metals concentrations, free residual chlorine and water temperature in hot water distribution systems (WDS). Investigations were performed on a large number of hot water samples taken from taps in kitchens and bathrooms in hotels and homes for the elderly and disabled in the Split region. Of the 127 hot water samples examined, 12 (9.4%) were positive for [i]Legionella[/i] spp. with median values concentration of 450 cfu × L[sup]-1[/sup] . Among positive isolates, 10 (83.3%) were [i]L. pneumophila[/i] sg 1, and two of them (16.6%) belonged to the genera [i]L. pneumophila[/i] sg 2–14. The positive correlation between the water temperature, iron and manganese concentrations, and [i]L. pneumophila[/i] contamination was proved by statistical analysis of the experimental data. On the contrary, zinc and free residual chlorine had no observed influence on the presence of [i]L. pneumophila[/i]. The presence of heavy metals in water samples confirms the corrosion of distribution system pipes and fittings, and suggests that metal plumbing components and associated corrosion products are important factors in the survival and growth of [i]L. pneumophila[/i] in WDS.