The Research Of Legionella And Non-tuberculous Mycobacteria In Building Domestic Hot Water

Recently the emerging opportunistic pathogen Legionella and non-tuberculous mycobacteria which can cause human illness were detected in domestic hot water at home and abroad in succession.The infection of these two pathogens can cause a variety of life-threatening illness,and they spread by aerosol while using the hot water.In our country,there has been a large area of disease outbreak caused by using the domestic hot water which contaminated by such pathogens.As one main route of transmission,with the yearly increase of positive rate,pathogenic rate,and fatality rate of Legionella and non-tuberculous mycobacteria,domestic hot water quality security deserves more attention.This study selected 5 types of building include residence,hospital,hotel,office building and public bathroom of college a total of 22 sampling points in Beijing,all the buildings were equipped with central hot water supply system,using laboratory test and rapid on-site test two detection methods to investigate Legionella and non-tuberculous mycobacteria contaimination and building domestic hot water quality,analysis the impact of domestic hot water quality on the two opportunistic pathogens,main conclusions are drawn as follows:(1)Legionella and non-tuberculous mycobacteria positive samples were detected in the domestic hot water of residence and hotels.It was independence of water supply subarea and the distribution of floors and rooms,these two opportunistic pathogens could generally existed in the domestic hot water with no distribution rules.(2)The results of laboratory detection indicated that 31.82%of the buildings identified positive samples for Legionella,in which 47.83%of the samples were contaminated;22.73%of the buildings identified positive samples for non-tuberculous mycobacteria,in which 53.85%of the samples were contaminated;in all the buildings,the rate of Legionella and non-tuberculous mycobacteria simultaneous positive is 13.64%,accounting for 27.27%and 42.86%of the buildings in which Legionella and non-tuberculous mycobacteria were detected.Hotels were severely contaminated,in which Legionella positive samples accounted for 85.71%of the total number of positive samples,non-tuberculous mycobacteria positive samples accounted for 80%of the total number of positive samples.(3)There were some differences between the results of laboratory test and rapid on-site test,the rapid on-site equipment was influenced by many factors of the sampling site environment.Because of the results have some limitations,rapid on-site test can be used for reference analysis of Legionella contamination trends.(4)The physicochemical and microbial parameters of domestic hot water quality have great influence on the growth of Legionella and non-tuberculous mycobacteria,water temperature,free chlorine residual and dissolved oxygen are the key risk factors for the growth and colonization of these two opportunistic pathogens in domestic hot water,it is necessary to raise water temperature and increase the content of free residual chlorine and dissolved oxygen.(5)In addition,the turbidity,organic matter content,conductivity and total dissolved solids content in domestic hot water should be reduced as low as possible,slow down the impact of water quality on corrosion and scaling of the pipeline,inhibit the growth of Legionella and non-tuberculous mycobacteria in building domestic hot water.