Thermal disinfection of hotels, hospitals, and athletic venues hot water distribution systems contaminated by Legionella species

Abstract

Legionella spp. ( >= 500 cfu liter(-1)) were detected in 92 of 497 water distribution systems (WDS) examined. Thermal disinfection was applied at 33 WDS. After the first and second application of the disinfection procedure, 15 (45.4%) and 3 (9%) positive for remedial actions WDS were found, respectively Legionella pneumophila was more resistant to thermal disinfection than Legionella non-pneumophila spp. (relative risk [RR] = 5.4, 95% confidence intervals [CI] = 1-35). WDS of hotels with oil heater were more easily disinfected than those with electrical or solar heater (RR = 0.4 95% CI = 0.2-0.8). Thermal disinfection seems not to be efficient enough to eliminate legionellae, unless repeatedly applied and in combination with extended heat flushing, and faucets chlorine disinfection.