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Water Quality and Microbial Dynamics in a Large Building Hot Water System and Managing Potential Risk Associated with Legionella - Atlanta
Citation:
Gomez-Alvarez, V., M. Berberich, L. Boczek, D. King, A. Pemberton, S. Pfaller, M. Rodgers, J. W. SANTO-DOMINGO, AND R. Revetta. Water Quality and Microbial Dynamics in a Large Building Hot Water System and Managing Potential Risk Associated with Legionella - Atlanta. ASM Microbe 2018, Atlanta,GA, June 07 - 11, 2018.
Impact/Purpose:
The purpose of this research is to add to our knowledge of premise plumbing (PP), which the water quality in premise plumbing is not monitored by U.S. EPA regulation with the exception of the Lead and Copper Rule. Because public health data shows that a significant fraction of the nation’s waterborne disease outbreaks are attributable to premise plumbing systems, it is important to understand the characteristics of these systems which amplify the potential public health risk relative to the drinking water distribution system.
Description:
Premise plumbing (PP) includes that portion of the drinking water distribution system (DWDS) connected via the service line to houses and other buildings. Water quality in PP is not monitored by U.S. EPA regulation with the exception of the Lead and Copper Rule. Because public health data shows that a significant fraction of the nation’s waterborne disease outbreaks are attributable to PP systems, it is important to understand the characteristics of these systems which amplify the potential public health risk relative to the DWDS. The present study was conducted in a 40-year-old large building supplied with treated chlorinated water with a main and secondary hot water network. We used physico-chemical parameters, heterotrophic plate counts (HPC), and 16S rRNA sequencing data to generate water quality profiles of the bulk water (BW), first-draw (FD) and flushed water (FW) at the tap, and principal, secondary and return loops of a hot water system. In addition, we investigated the abundance of Legionella using quantitative real-time PCR (qPCR) and Legiolert/Quanti-Tray® for Most Probable Number (MPN) enumeration, and the genetic diversity of the L. pneumophila community. Multivariate analysis based on 16S rRNA-encoding gene sequences identified five major clusters consistent with section/zones and hot water network. Representatives that explained the dissimilarity (SIMPER analysis) were associated with Alphaproteobacteria (45%), Cyanobacteria (17%), Actinobacteria (14%), Planctomycetia (11%), Betaproteobacteria (6%) and Gammaproteobacteria (3%). Furthermore, temporal variations in waterborne and opportunistic pathogen populations (Legionella, Mycobacterium and Pseudomonas) were observed among the five clusters. The Legionella population was dominated by L. pneumophila and identified as serotype 1 by agglutination and genomic analysis. FD samples from taps showed the highest counts of Legionella (≈1457 MPN/100mL) with a decrease in disinfectant residual (0.04 mg Cl2/L) and temperature (21.1°C). Legionella numbers tended to decline (290 MPN/100mL), and the temperature (46.2°C) and disinfectant residual (0.12 mg Cl2/L) increased with flushing. In this study water quality was found to deteriorate due to stagnation and continuous temperature monitoring revealed inconsistent flow patterns in the hot water system, which produced temperature zones that differed significantly from the hot water tank. Overall, these results provide an ecological insight of the microbial community and the potential risk associated with Legionella.