engleski

Presence of bacteria Legionella spp. in warm tap water in relation to heavy metals

The aim of this paper is to assess whether heavy metals influence the presence of Legionella spp. in water supply. Legionary disease has public health significance because of hard clinical picture and possible lethal issue. Important factors for survival Legionella spp. are physical chemical properties of the water (pH and mineral content, heavy metals), materials of the system, design of the system, furring, corrosion and dead-ends. A biofilm is result from colonization of mineral and organic deposits on surfaces in contact with by microorganisms present in the water. Human activities and natural causes influence the formation of the bio-aerosols which when inhaled, create preconditions for infection. Technical measures, such as flushing pipelines, have been devised to limit the infection risks in hot water. These measures have to be carried out at those high-risk facilities (saunas, swimming pools, jacuzzis). By performing research we can conclude whether the intervention to protect or improve the human health is necessary or whether the previous interventions have been successful. Hot water samples (121) were taken from three hotels in the Split-Dalmatia County, Croatia in the period from January 2011 to December 2011. The chemical analysis included concentrations of iron, zinc, copper and manganese. Cultivation and identification Legionella spp. followed the ISO 11731 standard. Final results are obtained by detailed statistical analysis of available data. The results were analyzed by the chi-square test, followed by statistical analysis at confidence levels p<0.05 with the aim of identification of possible connection of heavy metals concentrations with the Legionella spp. counts. Legionella spp. was confirmed in 13.2% analyzed samples. A statistically significant relation between iron (ρ = 0.271, p = 0.002), copper (ρ = 0.309, p = 0.005), manganese (ρ = 0.391, p = 0.001) and the presence of Legionella spp. was proven. No statistically significant correlation between microbiological findings and the zinc (ρ = 0.094, p = 0.129) in the samples. Higher concentrations of Fe, Cu and Mn were in accordance with the corrosion of the metal piping system and with reduced water flow, which favoured conditions for the growth and breeding of Legionella spp. obtained results indicated that further interventions are required for the protection of the human health. Furthermore this investigation provides the basis for design and subsequent scrutiny of pertinent chemical water treatment technologies.

tap water; heavy metals; biofilm; Legionella spp.

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