水道直結式ミスト発生装置の維持管理方法について

濱武 通子, 青木 梨絵, 山﨑 貢, 大西 賢治郎, 松本 一年

Objectives Water mist is usually generated using equipment directly connected to the water tap, as its installation is relatively easy. However, there is no legal regulation regarding the maintenance of this equipment, and the quality of the mist has not been sufficiently well investigated. In this study, we sought to establish methods that allow the hygienic maintenance of this equipment.Methods We monitored the use of the mist generating equipment in five of the 61 institutions in the jurisdiction of Ichinomiya Health Center, examined the resulting water quality, and tested for Legionella bacteria in the mist. If equipment was found to contain bacteria, the contaminated part was identified by counting the number of bacteria in the water after sequentially washing and disinfecting parts of the equipment. We also identified the predominant bacterial species.Results In the water mists from three of 5 institutions, the number of bacteria greatly exceeded that permitted for drinking-water, even though the residual chlorine level was >0.1 mg/l. However, no Legionella bacteria were detected. Brevundimonas species were predominant in the water mists at each institute. The hose was found to be the contaminated component in each case.Conclusion Our findings suggest that the number of bacteria in the water mist exceeded the drinking-water quality standard, even with a residual chlorine level of >0.1 mg/l. This study also revealed the importance of the continued drainage of water, following suitable cleaning and disinfection for maintenance of the mist-generating equipment.