Water Quality Control in the Water Supply System for the Purpose of Preventing Legionnaires’ Disease

The contamination of drinking water presents an important public health concern throughout the world. Microbial hazards make the largest contribution to waterborne disease in developed and developing countries. Legionella bacterium, the fundamental agent of Legionnaires’ disease, is a water-based organism that causes infection when inhaled in an aerosol form. Main factors influencing the survival of Legionella spp. are: physical and chemical properties of the water (pH value, mineral content, and presence of heavy metals), materials used in the system, system design, furring, corrosion, and dead-ends. These bacteria are transmitted during the showering by inhalation of contaminated water droplets and the highest risk of infection with a subsequent death is encountered among immunocompromised and elderly water consumers. The control of the disease has been one of the major problems in countries with low- and middle-income economies, including Croatia. The most frequently used approach to disinfect the system is a daily increase of water temperature in the heating coil. However, due to the economic issues, the residents frequently request house managers to decrease the temperature of hot water systems leading to an increased system contamination and subsequent human infections.