1
|
Grimard-Conea M, Bédard E, Prévost M. Can free chlorine residuals entering building plumbing systems really be maintained to prevent microbial growth? THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 939:173651. [PMID: 38821274 DOI: 10.1016/j.scitotenv.2024.173651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/22/2024] [Accepted: 05/28/2024] [Indexed: 06/02/2024]
Abstract
Secondary disinfection aims to prevent microbial regrowth during distribution by maintaining disinfectant residuals in water systems. However, multi-factorial interactions contribute to free chlorine decay in distribution systems, and even more so in building plumbing. Assembling 1737 samples from nine large institutional buildings, a meta-analysis was conducted to determine whether building managers can actively rely on incoming free chlorine residuals to prevent in-building microbial amplification. Findings showed that free chlorine concentrations in first draws met the 0.2 mg/L common guide level in respectively 26 %, 6 % and 2 % of cold, tepid and hot water samples, whereas flushing for 2-60 min only significantly increased this ratio in cold water (83 %), without reaching background levels found in service lines. Free chlorine was significantly but weakly (R≤ 0.2) correlated to adenosine triphosphate, heterotrophic plate count and total and intact cell counts, thus evidencing that residuals contributed to decreased culturable and viable biomass. Detection of culturable Legionella pneumophila spanning over a 4-log distribution solely occurred when free chlorine levels were below 0.2 mg/L, but no such trend could be distinguished clearly for culturable Pseudomonas aeruginosa. Water temperatures below 20 °C and >60 °C also completely prevented L. pneumophila detection. Overall, the majority of elevated microbial counts were measured in distal sites and in tepid and hot water, where free chlorine is less likely to be present due to stagnation and increased temperature. Therefore, building managers cannot solely rely on this chemical barrier to mitigate bacterial growth in bulk water.
Collapse
Affiliation(s)
| | - Emilie Bédard
- Department of Civil Engineering, Polytechnique Montreal, Montreal, QC H3C 3A7, Canada.
| | - Michèle Prévost
- Department of Civil Engineering, Polytechnique Montreal, Montreal, QC H3C 3A7, Canada.
| |
Collapse
|
2
|
Ra K, Proctor C, Ley C, Angert D, Noh Y, Odimayomi T, Whelton AJ. Four buildings and a flush: Lessons from degraded water quality and recommendations on building water management. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2024; 18:100314. [PMID: 37854462 PMCID: PMC10579424 DOI: 10.1016/j.ese.2023.100314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 09/07/2023] [Accepted: 09/11/2023] [Indexed: 10/20/2023]
Abstract
A reduction in building occupancy can lead to stagnant water in plumbing, and the potential consequences for water quality have gained increasing attention. To investigate this, a study was conducted during the COVID-19 pandemic, focusing on water quality in four institutional buildings. Two of these buildings were old (>58 years) and large (>19,000 m2), while the other two were new (>13 years) and small (<11,000 m2). The study revealed significant decreases in water usage in the small buildings, whereas usage remained unchanged in the large buildings. Initial analysis found that residual chlorine was rarely detectable in cold/drinking water samples. Furthermore, the pH, dissolved oxygen, total organic carbon, and total cell count levels in the first draw of cold water samples were similar across all buildings. However, the ranges of heavy metal concentrations in large buildings were greater than observed in small buildings. Copper (Cu), lead (Pb), and manganese (Mn) sporadically exceeded drinking water limits at cold water fixtures, with maximum concentrations of 2.7 mg Cu L-1, 45.4 μg Pb L-1, 1.9 mg Mn L-1. Flushing the plumbing for 5 min resulted in detectable residual at fixtures in three buildings, but even after 125 min of flushing in largest and oldest building, no residual chlorine was detected at the fixture closest to the building's point of entry. During the pandemic, the building owner conducted fixture flushing, where one to a few fixtures were operated per visit in buildings with hundreds of fixtures and multiple floors. However, further research is needed to understand the fundamental processes that control faucet water quality from the service line to the faucet. In the absence of this knowledge, building owners should create and use as-built drawings to develop flushing plans and conduct periodic water testing.
Collapse
Affiliation(s)
- Kyungyeon Ra
- Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN, 47907, USA
| | - Caitlin Proctor
- Agricultural and Biological Engineering, Division of Environmental and Ecological Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Christian Ley
- Division of Environmental and Ecological Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Civil and Environmental Engineering, University of Colorado, 1111 Engineering Drive, Boulder, CO, 80309, USA
| | - Danielle Angert
- Division of Environmental and Ecological Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Civil, Architectural and Environmental Engineering, University of Texas, 301E E Dean Keeton Street, Austin, TX, 78712, USA
| | - Yoorae Noh
- Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN, 47907, USA
| | - Tolulope Odimayomi
- Division of Environmental and Ecological Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Civil and Environmental Engineering, Virginia Tech, 750 Drillfield Drive, Blacksburg, VA, 24061, USA
| | - Andrew J. Whelton
- Lyles School of Civil Engineering, Division of Environmental and Ecological Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN, 47907, USA
| |
Collapse
|
3
|
Hozalski RM, Zhao X, Kim T, LaPara TM. On-site filtration of large sample volumes improves the detection of opportunistic pathogens in drinking water distribution systems. Appl Environ Microbiol 2024; 90:e0165823. [PMID: 38236032 PMCID: PMC10880612 DOI: 10.1128/aem.01658-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 12/06/2023] [Indexed: 01/19/2024] Open
Abstract
In this study, we compared conventional vacuum filtration of small volumes through disc membranes (effective sample volumes for potable water: 0.3-1.0 L) with filtration of high volumes using ultrafiltration (UF) modules (effective sample volumes for potable water: 10.6-84.5 L) for collecting bacterial biomass from raw, finished, and tap water at seven drinking water systems. Total bacteria, Legionella spp., Legionella pneumophila, Mycobacterium spp., and Mycobacterium avium complex in these samples were enumerated using both conventional quantitative PCR (qPCR) and viability qPCR (using propidium monoazide). In addition, PCR-amplified gene fragments were sequenced for microbial community analysis. The frequency of detection (FOD) of Legionella spp. in finished and tap water samples was much greater using UF modules (83% and 77%, respectively) than disc filters (24% and 33%, respectively). The FODs for Mycobacterium spp. in raw, finished, and tap water samples were also consistently greater using UF modules than disc filters. Furthermore, the number of observed operational taxonomic units and diversity index values for finished and tap water samples were often substantially greater when using UF modules as compared to disc filters. Conventional and viability qPCR yielded similar results, suggesting that membrane-compromised cells represented a minor fraction of total bacterial biomass. In conclusion, our research demonstrates that large-volume filtration using UF modules improved the detection of opportunistic pathogens at the low concentrations typically found in public drinking water systems and that the majority of bacteria in these systems appear to be viable in spite of disinfection with free chlorine and/or chloramine.IMPORTANCEOpportunistic pathogens, such as Legionella pneumophila, are a growing public health concern. In this study, we compared sample collection and enumeration methods on raw, finished, and tap water at seven water systems throughout the State of Minnesota, USA. The results showed that on-site filtration of large water volumes (i.e., 500-1,000 L) using ultrafiltration membrane modules improved the frequency of detection of relatively rare organisms, including opportunistic pathogens, compared to the common approach of filtering about 1 L using disc membranes. Furthermore, results from viability quantitative PCR (qPCR) with propidium monoazide were similar to conventional qPCR, suggesting that membrane-compromised cells represent an insignificant fraction of microorganisms. Results from these ultrafiltration membrane modules should lead to a better understanding of the microbial ecology of drinking water distribution systems and their potential to inoculate premise plumbing systems with opportunistic pathogens where conditions are more favorable for their growth.
Collapse
Affiliation(s)
- Raymond M. Hozalski
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota Twin Cities, St. Paul, Minnesota, USA
| | - Xiaotian Zhao
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
| | - Taegyu Kim
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
| | - Timothy M. LaPara
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota Twin Cities, St. Paul, Minnesota, USA
| |
Collapse
|
4
|
Oh Y, Sangsanont J, Woo H, Boczek LA, Linden KG, Ryu H. Inactivation efficacy and mechanisms of wavelength-specific UV sources for various strains of Legionella pneumophila serogroup 1. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 907:167781. [PMID: 37844643 DOI: 10.1016/j.scitotenv.2023.167781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/23/2023] [Accepted: 10/10/2023] [Indexed: 10/18/2023]
Abstract
Infections of Legionnaires' disease in the United States caused by Legionella have increased ninefold between the years 2000-2018. Legionella harbored in biofilms or inside amoeba within premise plumbing can be more resistant to disinfectants, thus causing treatment challenges. Ultraviolet-light emitting diodes (UV-LEDs) are an emerging water disinfection technology with several advantages over conventional UV lamps. In this study, we evaluated the effects of UV-LEDs (255, 265, and 285 nm), a low-pressure (LP) mercury UV lamp (254 nm), and a bandpass filtered medium-pressure (MP) mercury UV lamp (220 nm) on properties and inactivation of three strains of L. pneumophila serogroup 1. The UV-LEDs emitting at 255 and 265 nm showed greater inactivation performance against all the strains compared to the UV-LED at 285 nm and the LP UV lamp at 254 nm. Our results showed that strains of the same serogroup exhibited different UV sensitivities. Analyses of DNA and protein damage revealed that UV exposure using 254, 255, and 265 nm predominantly causes DNA damage, while protein damage is predominant at 220 nm. Both DNA and protein damage were observed at 285 nm, but the extent of DNA damage was relatively less significant compared to the other wavelengths. Electric energy consumption analysis showed that water treatment using UV-LEDs is currently unsatisfactory compared to conventional LP UV lamps due to the mediocre wall plug efficiency (WPE) of UV-LEDs. However, recent studies indicate that the WPE of UV-LEDs is continuously improving. Overall, our study highlights that UV-LEDs are a promising technology for inactivating waterborne pathogens and have the potential to replace existing UV mercury lamps for water disinfection applications.
Collapse
Affiliation(s)
- Yoontaek Oh
- United States Environmental Protection Agency, Office of Research and Development, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, United States of America; Pegasus Technical Services, Inc., 26 W. Martin Luther King Dr., Cincinnati, OH 45268, United States of America
| | - Jatuwat Sangsanont
- Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, UCB 428, Boulder, CO 80309, United States of America; Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Hyoungmin Woo
- United States Environmental Protection Agency, Office of Research and Development, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, United States of America
| | - Laura A Boczek
- United States Environmental Protection Agency, Office of Research and Development, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, United States of America
| | - Karl G Linden
- Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, UCB 428, Boulder, CO 80309, United States of America.
| | - Hodon Ryu
- United States Environmental Protection Agency, Office of Research and Development, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, United States of America.
| |
Collapse
|
5
|
Donohue MJ, Pham M, Brown S, Easwaran KM, Vesper S, Mistry JH. Water quality influences Legionella pneumophila determination. WATER RESEARCH 2023; 238:119989. [PMID: 37137207 PMCID: PMC10351031 DOI: 10.1016/j.watres.2023.119989] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 04/18/2023] [Accepted: 04/20/2023] [Indexed: 05/05/2023]
Abstract
Legionellosis is a respiratory disease of public health concern. The bacterium Legionella pneumophila is the etiologic agent responsible for >90% of legionellosis cases in the United States. Legionellosis transmission primarily occurs through the inhalation or aspiration of contaminated water aerosols or droplets. Therefore, a thorough understanding of L. pneumophila detection methods and their performance in various water quality conditions is needed to develop preventive measures. Two hundred and nine potable water samples were collected from taps in buildings across the United States. L. pneumophila was determined using three culture methods: Buffered Charcoal Yeast Extract (BCYE) culture with Matrix-assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) identification, Legiolert® 10- and 100-mL tests, and one molecular method: quantitative Polymerase Chain Reaction (qPCR) assay. Culture and molecular positive results were confirmed by secondary testing including MALDI-MS. Eight water quality variables were studied, including source water type, secondary disinfectant, total chlorine residual, heterotrophic bacteria, total organic carbon (TOC), pH, water hardness, cold- and hot-water lines. The eight water quality variables were segmented into 28 categories, based on scale and ranges, and method performance was evaluated in each of these categories. Additionally, a Legionella genus qPCR assay was used to determine the water quality variables that promote or hinder Legionella spp. occurrence. L. pneumophila detection frequency ranged from 2 to 22% across the methods tested. Method performance parameters of sensitivity, specificity, positive and negative predictive values, and accuracy were >94% for the qPCR method but ranged from 9 to 100% for the culture methods. Water quality influenced L. pneumophila determination by culture and qPCR methods. L. pneumophila qPCR detection frequencies positively correlated with TOC and heterotrophic bacterial counts. The source water-disinfectant combination influenced the proportion of Legionella spp. that is L. pneumophila. Water quality influences L. pneumophila determination. To accurately detect L. pneumophila, method selection should consider the water quality in addition to the purpose of testing (general environmental monitoring versus disease-associated investigations).
Collapse
Affiliation(s)
- Maura J Donohue
- United States Environmental Protection Agency, Cincinnati, OH 45268, USA.
| | - Maily Pham
- United States Environmental Protection Agency, Cincinnati, OH 45268, USA
| | - Stephanie Brown
- United States Environmental Protection Agency, Cincinnati, OH 45268, USA
| | | | - Stephen Vesper
- United States Environmental Protection Agency, Cincinnati, OH 45268, USA
| | - Jatin H Mistry
- United States Environmental Protection Agency, Region 6, Dallas, TX 75270, USA
| |
Collapse
|
6
|
Grimard-Conea M, Prévost M. Controlling Legionella pneumophila in Showerheads: Combination of Remedial Intervention and Preventative Flushing. Microorganisms 2023; 11:1361. [PMID: 37374862 DOI: 10.3390/microorganisms11061361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 05/17/2023] [Accepted: 05/20/2023] [Indexed: 06/29/2023] Open
Abstract
Shock chlorination and remedial flushing are suggested to address Legionella pneumophila (Lp) contamination in buildings or during their (re)commissioning. However, data on general microbial measurements (adenosine tri-phosphate [ATP], total cell counts [TCC]), and the abundance of Lp are lacking to support their temporary implementation with variable water demands. In this study, the weekly short-term (3-week) impact of shock chlorination (20-25 mg/L free chlorine, 16 h) or remedial flushing (5-min flush) combined with distinct flushing regimes (daily, weekly, stagnant) was investigated in duplicates of showerheads in two shower systems. Results showed that the combination of stagnation and shock chlorination prompted biomass regrowth, with ATP and TCC in the first draws reaching large regrowth factors of 4.31-7.07-fold and 3.51-5.68-fold, respectively, from baseline values. Contrastingly, remedial flushing followed by stagnation generally resulted in complete or larger regrowth in Lp culturability and gene copies (gc). Irrespective of the intervention, daily flushed showerheads resulted in significantly (p < 0.05) lower ATP and TCC, as well as lower Lp concentrations than weekly flushes, in general. Nonetheless, Lp persisted at concentrations ranging from 11 to 223 as the most probable number per liter (MPN/L) and in the same order of magnitude (103-104 gc/L) than baseline values after remedial flushing, despite daily/weekly flushing, unlike shock chlorination which suppressed Lp culturability (down 3-log) for two weeks and gene copies by 1-log. This study provides insights on the most optimal short-term combination of remedial and preventative strategies that can be considered pending the implementation of suitable engineering controls or building-wide treatment.
Collapse
Affiliation(s)
- Marianne Grimard-Conea
- Industrial Chair in Drinking Water, Department of Civil, Mining and Geological Engineering, Polytechnique Montreal, Montreal, QC H3C 3A7, Canada
| | - Michèle Prévost
- Industrial Chair in Drinking Water, Department of Civil, Mining and Geological Engineering, Polytechnique Montreal, Montreal, QC H3C 3A7, Canada
| |
Collapse
|
7
|
Evaluation of a Most Probable Number Method for Detection and Quantification of Legionella pneumophila. Pathogens 2022; 11:pathogens11070789. [PMID: 35890033 PMCID: PMC9324539 DOI: 10.3390/pathogens11070789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/02/2022] [Accepted: 07/07/2022] [Indexed: 11/17/2022] Open
Abstract
The detection and enumeration of Legionella pneumophila (L. pneumophila) in water is crucial for water quality management, human health and has been a research hotspot worldwide. Due to the time-consuming and complicated operation of the plate culture method, it is necessary to adopt a fast and effective method for application. The present study aimed to comprehensively evaluate the performance and applicability of the MPN method by comparing its qualitative and quantitative results with the GB/T 18204.5-2013 and ISO methods, respectively. The qualitative results showed that 372 samples (53%) were negative for both methods; 315 samples (45%) were positively determined by the MPN method, compared with 211 samples (30%) using GB/T 18204.5-2013. The difference in the detection rate between the two methods was statistically significant. In addition, the quantitative results showed that the concentration of L. pneumophila by the MPN method was greater than ISO 11731 and the difference was statistically significant. However, the two methods were different but highly correlated (r = 0.965, p < 0.001). The specificity and sensitivity of the MPN method were 89.85% and 95.73%, respectively. Overall, the results demonstrated that the MPN method has higher sensitivity, a simple operation process and good application prospects in the routine monitoring of L. pneumophila from water samples.
Collapse
|
8
|
Variable Legionella Response to Building Occupancy Patterns and Precautionary Flushing. Microorganisms 2022; 10:microorganisms10030555. [PMID: 35336130 PMCID: PMC8950775 DOI: 10.3390/microorganisms10030555] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 02/21/2022] [Accepted: 02/26/2022] [Indexed: 02/04/2023] Open
Abstract
When stay-at-home orders were issued to slow the spread of COVID-19, building occupancy (and water demand) was drastically decreased in many buildings. There was concern that widespread low water demand may cause unprecedented Legionella occurrence and Legionnaires’ disease incidence. In lieu of evidenced-based guidance, many people flushed their water systems as a preventative measure, using highly variable practices. Here, we present field-scale research from a building before, during, and after periods of low occupancy, and controlled stagnation experiments. We document no change, a > 4-log increase, and a > 1.5-log decrease of L. pneumophila during 3- to 7-week periods of low water demand. L. pneumophila increased by > 1-log after precautionary flushing prior to reoccupancy, which was repeated in controlled boiler flushing experiments. These results demonstrate that the impact of low water demand (colloquially called stagnation) is not as straight forward as is generally assumed, and that some flushing practices have potential unintended consequences. In particular, stagnation must be considered in context with other Legionella growth factors like temperature and flow profiles. Boiler flushing practices that dramatically increase the flow rate and rapidly deplete boiler temperature may mobilize Legionella present in biofilms and sediment.
Collapse
|