Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University , 418 Durham Hall, Blacksburg, Virginia 24061, United States.
Environ Sci Technol. 2017 Jun 20;51(12):7065-7075. doi: 10.1021/acs.est.6b05616. Epub 2017 Jun 1.
Complexities associated with drinking water plumbing systems can result in undesirable interactions among plumbing components that undermine engineering controls for opportunistic pathogens (OPs). In this study, we examine the effects of plumbing system materials and two commonly applied disinfectants, copper and chloramines, on water chemistry and the growth of Legionella and mycobacteria across a transect of bench- and pilot-scale hot water experiments carried out with the same municipal water supply. We discovered that copper released from corrosion of plumbing materials can initiate evolution of >1100 times more hydrogen (H) from water heater sacrificial anode rods than does presence of copper dosed as soluble cupric ions. H is a favorable electron donor for autotrophs and causes fixation of organic carbon that could serve as a nutrient for OPs. Dosed cupric ions acted as a disinfectant in stratified stagnant pipes, inhibiting culturable Legionella and biofilm formation, but promoted Legionella growth in pipes subject to convective mixing. This difference was presumably due to continuous delivery of nutrients to biofilm on the pipes under convective mixing conditions. Chloramines eliminated culturable Legionella and prevented L. pneumophila from recolonizing biofilms, but M. avium gene numbers increased by 0.14-0.76 logs in the bulk water and were unaffected in the biofilm. This study provides practical confirmation of past discrepancies in the literature regarding the variable effects of copper on Legionella growth, and confirms prior reports of trade-offs between Legionella and mycobacteria if chloramines are applied as secondary disinfectant residual.
饮用水管道系统的复杂性可能导致管道组件之间产生不理想的相互作用，从而破坏针对机会性病原体 (OPs) 的工程控制措施。在这项研究中，我们研究了管道系统材料以及两种常用消毒剂——铜和氯胺对水化学以及军团菌和分枝杆菌生长的影响，该研究是使用相同的市政供水在一系列 bench- 和 pilot-scale 热水实验中进行的。我们发现，与添加可溶性铜离子相比，管道材料腐蚀释放的铜可以使热水器牺牲阳极棒从水中产生多出 1100 多倍的氢气 (H)。H 是自养生物的理想电子供体，并导致有机碳的固定，这可能成为 OPs 的营养物质。投加的铜离子在分层停滞管道中充当消毒剂，抑制可培养的军团菌和生物膜形成，但促进了在对流混合条件下的管道中的军团菌生长。这种差异可能是由于在对流混合条件下，连续向管道生物膜提供营养物质所致。氯胺消除了可培养的军团菌并阻止了嗜肺军团菌重新定殖生物膜，但在 bulk water 中，鸟分枝杆菌基因数量增加了 0.14-0.76 个对数，而在生物膜中则没有受到影响。这项研究为过去文献中关于铜对军团菌生长的可变影响的差异提供了实际确认，并证实了如果使用氯胺作为二级消毒剂残留，则军团菌和分枝杆菌之间存在权衡取舍的先前报告。
