The detection of Legionella pneumophila in air-conditioning cooling towers related with the change of temperature

• Main Authors: I-Ching Chen, 陳伊菁
• Other Authors: P.C. HSU
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/51300989792753061057

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程研究所 === 101 === This study investigates L. pneumophila detection, which is performed every 6 mo, in the air-conditioning cooling towers of a certain electronics factory. Furthermore, we also examine the correlation between the atmospheric temperature inside and outside of the cooling tower tanks, and water flow. The research subjects are 48 air-conditioning cooling towers located in a certain electronics factory. The pipes of 24 towers are connected to one tower; thus, temperature and water flow measurements were only recorded for 2 towers (i.e., the south and north towers). In this study, we learned that L. pneumophila can be detected during winter. To elucidate the relationship between the detection results and temperature and water flow, atmospheric temperature and flow measurements for in and outside the tanks were recorded every 2 h for 5 d from January 28, 2013 to February 1, 2013. The time points at which the temperature was measured included the following: 7:00 AM, 9:00 AM, 11:00 AM, 1:00 PM, 3:00 PM, 5:00 PM, and 7:00 PM. Examining the maintenance records showed that for the air-conditioning cooling towers in which large amounts of L. pneumophila were detected, chemical bactericides had not been added for 2 mo prior to detection. Thus, we assert that adding chemical bactericides to cooling towers can effectively inhibit the growth of L. pneumophila. For air-conditioning cooling towers in which low amounts of Legionella pneumophila were detected, we found that the short-period water circulation switch had been activated before detection. Thus, short cycling in cooling towers is related to the growth of L. pneumophila. According to statistical analysis, atmospheric temperature in and outside the tanks at various sampling times was significantly different (p < 0.05). Cooling tower short-period water circulation, sampling times (7:00 AM, 9:00 AM, 5:00 PM, and 7:00 PM), and atmospheric temperature inside the tanks were also significantly different (p < 0.05). Linear regression analysis showed that atmospheric temperature in and outside the tanks demonstrated a significant correlation (p < 0.005); however, the r value for atmospheric temperature outside the tanks was 0.94 and the r value for atmospheric temperature inside the tanks was 0.379. The results for the temperature measurements showed that the temperature in flowing water was higher than that in stagnant water. In summary, regularly adding chemical bactericides in air-conditioning cooling towers can effectively minimize the growth of L. pneumophila, and activating water cycling during winter reduces L. pneumophila growth. Moreover, atmospheric temperature can be used to estimate temperature outside the tanks, but temperature inside the tanks must be measured. The results of this study can serve as a reference for environmental health management and control of L. pneumophila growth in air-conditioning cooling towers.