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Investigating water safety in multi-purpose buildings used as an elementary school and plumbing remediation effectiveness [1]

['Kyungyeon Ra', 'Lyles School Of Civil Engineering', 'Purdue University', 'West Lafayette', 'In', 'United States Of America', 'Caitlin Proctor', 'Agricultural', 'Biological Engineering', 'Division Of Environmental']

Date: 2023-08

Abstract Three buildings that were repurposed for use as an elementary school were shutdown for three months in response to the pandemic. Building cold and hot water quality was monitored before reopening to detect and resolve chemical and microbiological problems. The authors collected first draw pre-flush and post-flush water samples. First draw water samples did not contain detectable disinfectant residual, but nickel and lead sometimes exceeded the health-based action limits for cold water (max. 144 μg Ni/L, 3.4 μg Pb/L). Stagnant cold water at a bathroom sink (188 MPN/100 mL) and drinking water fountain (141.6 MPN/100 mL), in the same building, exceeded the L. pneumophila thresholds advised by the World Health Organization (WHO) (10 CFU/mL) and American Industrial Hygiene Association (AIHA) (100 CFU/mL). Fixture flushing was conducted to remove cold and hot stagnant water and no L. pneumophila was detected immediately after flushing. Two weeks after no subsequent building water use, chemical and microbiological contaminant levels were found to be similar to levels prior to flushing with one exception. The maximum L. pneumophila level (kitchen sink, hot water: 61.1 MPN/100 mL) was found in a different building than the prior maximum detections. No repeat positive locations for L. pneumophila were found during the second visit, but new fixtures were positive the organism. When this study was conducted no evidence-based guidelines for plumbing recommissioning were available. A single plumbing flush reduced heavy metal and L. pneumophila levels below WHO and AIHA thresholds in all three buildings. Additional work is needed to examine the role of building size, type and plumbing design on fixture water quality in shutdown buildings.

Citation: Ra K, Proctor C, Ley C, Angert D, Noh Y, Isaacson K, et al. (2023) Investigating water safety in multi-purpose buildings used as an elementary school and plumbing remediation effectiveness. PLOS Water 2(7): e0000141. https://doi.org/10.1371/journal.pwat.0000141 Editor: Manuel Herrera, University of Cambridge, UNITED KINGDOM Received: December 14, 2022; Accepted: May 31, 2023; Published: July 6, 2023 Copyright: © 2023 Ra et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All data are provided as part of the submitted article. Funding: This work was supported by the U.S. Environmental Protection Agency (R836890 to AW) and National Science Foundation (CBET-2027049 and CBET-2039498 to AW and CP, and CBET-2214580 to AW). These organizations had no role in study design, data collection and analysis, decision to publish, or the preparation or approval of the manuscript. Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests. “AW and CP provided guidance to the U.S. Environmental Protection Agency and U.S. Centers for Disease Control and Prevention on their building water flushing guidance which was issued by the agencies during the conduct of the present study” as the manuscript indicated.

Introduction Water at schools can pose health risks to children, and U.S. schools have historically not been a focus of routine drinking water testing. School buildings also lack formal water management programs [1], and are not specifically regulated under the Safe Drinking Water Act (SDWA) [2]. Only about seven states and the District of Columbia require school water testing. Therefore, the act, type, and frequency of school water testing is primarily at the discretion of the building owners [2]. A 2019 U.S. study revealed that less than half of the schools surveyed conducted water quality testing (n = 514), 46% flushed drinking water outlets after periods of non-use, and even fewer (25%) required staff training on water quality maintenance (n = 520) [3]. Another 2019 survey found that for 25 states, uniformity of school water quality testing programs was lacking [4]. During the pandemic, school water safety concerns were raised due to the presence of stagnant water [5]. In Ohio, school custodians contracted Legionnaires Disease and one fatality occurred [6]. Elevated drinking water lead, copper and manganese levels are also known to pose health risks to children [7–9]. Because there were more than 124,000 U.S public and private schools shutdown in response to the pandemic [10], school water safety concerns became nationally important. During the pandemic, a federal watchdog agency warned that government building operators were not adequately testing water safety before reopening schools [11]. Prior to the pandemic it was well-known that stagnation could cause water quality deterioration in large buildings, and many studies were conducted during the pandemic to explore this phenomenon [11–23]. Disinfectant residual, such as free chlorine, in drinking water delivered to buildings is meant to help minimize microbiological growth. Within plumbing, disinfectant concentration decreases due to temperature, as well as reactions with bulk water constituents and plumbing surfaces. Chemical and microbiological quality can change in water heaters and water softeners within hours. Prior studies have shown that low water use can prompt greater cold and hot water copper and bacteria levels (Mycobacterium avium, Mycobacterium spp. Legionella spp., and total cell count [TCC]) [16, 23]. Leaching of metal contaminants like copper, lead, and zinc from plumbing is a known children’s health risk in drinking water [24–27]. Weekend stagnation can sometimes cause heavy metal concentrations to exceed health-based limits [28]. Stagnant cold and hot water can contain Legionella spp. and Mycobacterium avium [22]. Stagnant water has been found to contain greater concentrations of Legionella spp., Mycobacteria, heterotrophic plate counts [HPC], and TCC in building plumbing compared to flushed water samples [28–32]. At the time this study was initiated, there was no agreement on the actions needed to find and reduce chemical and microbiological health risks in school plumbing. During the pandemic, many guidelines were issued by local, state, federal agencies as well as trade associations and companies [33–39]. Instructions were often vague, different organizations contradicted other organizations, and guidance rarely recommended water testing [33]. Generally, removing stagnant water by flushing plumbing was recommended [34, 38, 39], though some organizations recommended shock disinfection [40–42]. Studies of buildings during the pandemic found that heavy metal and microbial contaminant concentrations were not reduced completely or the levels increased. In one study, flushing decreased lead concentration but 28 μg/L remained which is still above the American Academy of Pediatrics recommended limit of 1 μg/L [24]. In another study, copper and lead concentration significantly decreased after flushing but iron levels increased by 200% possibly due to scale destabilization [25]. In some studies most flushed water samples had lower Legionella spp. levels [27, 30], but sometimes these levels were greater after flushing [24]. Also reported was that Legionella spp. was not detected immediately after flushing, but was detected again two to four days later. For reference, the World Health Organization (WHO) and American Industrial Hygiene Association (AIHA) recommend shock disinfection when Legionella levels are greater than 10 CFU/mL [43] and 100 CFU/mL [40]. Specifically, AIHA [40] has recommends that when greater than 100 CFU/mL is found, “immediate steps to clean and disinfect the system” are required. Though, one study indicated “a gradual increase in water demand was more sufficient in changing waterborne microbial loads than a short-term fixture flushing for remediation” [44]. Another study also found that “regular flushing in low-use or low-flow [systems] is inefficient to control waterborne pathogen” [45]. The lack of specificity on school water sampling and plumbing remediation actions during low water use and building reopening is a gap in knowledge. The study goal was to better understand water quality in the shutdown buildings and the effectiveness of flushing to reducing chemical and microorganism levels at the fixtures. Specific research objectives were to (1) document chemical and microbiological first draw water quality after three months of stagnation in three separate school buildings in one property, (2) conduct flushing of each building water system and monitor flushing effectiveness, and (3) determine the limitations of flushing.

Materials and methods Water supply and site inspection The study site was an elementary school campus in Indiana with three detached buildings (Fig 1). The campus was served by a single public water system through two different service lines, each with a water meter. The public water system utilized eight groundwater wells and served water to about 35,000 people. Free chlorine disinfectant and a polyphosphate-orthophosphate blend of corrosion inhibitor were added to the water before water entered the water distribution system. In a separate study, service line water quality monitoring for one year was conducted in the same water distribution system 2.6 miles (4.2 km) away from the campus and the following water quality characteristics were reported (pH: 7.22 to 7.81; total Cl 2 : 0 to 2.10 mg/L; free Cl 2 : 0 to 1.40 mg/L; Dissolved oxygen [DO]: 4.50 to 11.12 mg/L) [18]. PPT PowerPoint slide

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TIFF original image Download: Fig 1. (a) Site property with building A, B and C with estimated location of public water supply pipe (blue), two water meters (sky blue circle) and service line to each building (sky blue) and where splits to deliver to building A (dotted sky blue), (b) Elkay drinking water fountains installed for kids’ height, (c) all classrooms had their own sinks, drinking water fountain, and appliances, (d) coffee maker connected to the plumbing in building A, and (e) particulates in the aerator before removal. https://doi.org/10.1371/journal.pwat.0000141.g001 None of the campus buildings were originally designed to be school buildings (Fig 1). Buildings A (2 floors, 2,423 m2) and B (1 floor, 1,024 m2) were constructed in 1966 as multi-purpose buildings on the property. In 2001, the property changed owners, buildings were renovated to be used as an elementary school, but the plumbing was not modified. In 2006, another building was constructed on the property (building C, 114 m2). Buildings A and B were served by a single service line entering the West side of the property with a water meter while building C was served by a service line on the North side of the property with a separate water meter. The estimated distance from the water meter to the building B was about 78 meters, and to building C was eight meters. Plumbing designs and components were relatively similar across buildings. Domestic water plumbing was soldered copper pipe with crosslinked polyethylene (PEX) faucet connectors and Elkay® drinking water fountains. Each building had a different volume water heater (A: 151 L, B: 113 L, C: 189 L). In building A there were two pressure tanks (179.8 L each) and single water softener. Buildings B and C did not have water softeners. In buildings A and B, each classroom had one sink, one mini- or typical size refrigerator, and dishwasher. In building A, the main faculty/staff break room had one refrigerator with an icemaker and coffee maker appliance connected to the plumbing. Building A had one classroom on the first floor, three classrooms on the second floor; building B had two classrooms, building C had two classrooms. At the playground, two outdoor drinking water fountains connected to building B’s plumbing. In mid-March 2020 the school shutdown for Spring Break, but then switched to online learning due to the pandemic. During the online learning period, students did not return to campus until mid-August 2020. The authors visited the site on June 19, 2020 for an initial inspection. During the initial inspection visit, the authors learned that even though the campus was closed from March to August, the building owner was using water from building C (hose spigot) to water the grass. Water used for irrigation occurred weekly starting in June. Through discussions, the authors learned that the building owner also flushed water from select fixtures on a few days in response to hearing that government agencies recommended schools flush fixtures in response to low occupancy. The school planned to reopen for in-person learning on July 1, 2020, but after authors’ initial investigation, the school did not reopen until mid-August. The building owner did not have as-built plumbing drawings or understand their buildings’ plumbing design or components. Prior to the author’s study, the building owner had never tested water from the plumbing except for drinking water lead samples collected a few years prior by a consultant. Water sampling and analysis approach The study period included mid-March 2020 to July 2020 (Fig 2). On June 26, 2020, the authors visited the property to collect samples at 9:00 am. First draw samples were collected, followed by samples collected during and after flushing. The authors returned to the buildings two weeks later and also collected first draw samples. At each building, cold water samples were collected first followed by hot water samples. Samples were collected from kitchen sinks, bathroom sinks, and drinking water fountains (S1 Table). The authors first sampled water in building C, followed by building B and then building A. From each fixture about 150 mL was first collected in a beaker for total chlorine, pH, temperature, and dissolved oxygen (DO) concentration followed by samples for [total or dissolved] metal concentration (125 mL for each), L. pneumophila by Legiolert (125 mL), total cell counts [TCC] (Two 15 mL), total organic carbon [TOC] concentration (125 mL). Approximately 1,000 mL was then flushed from each fixture followed by a sample collected for measuring total trihalomethanes concentration [TTHMs] (10 mL). Hot water samples were collected in the same order. All stagnant water samples were collected at a slow flow rate. For metal samples, 3N HCl was added to each bottle and for TOC samples, Na 2 SO 4 was added glass bottles. All samples were stored at 4⁰C until analysis. PPT PowerPoint slide

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TIFF original image Download: Fig 2. Flowchart of the research methodology. Building water use and water sampling activities ranged from March 2020 to July 2020. https://doi.org/10.1371/journal.pwat.0000141.g002 Onsite analysis for chlorine measurement was conducted using a HACH® DR300 Pocket Colorimeter with DPD total chlorine (detection limit = 0.02 mg/L as Cl 2 ). Water pH, temperature, and DO concentration were measured using HACH® SL1000 PPA Portable Parallel Analyzer. For heavy metals analysis, an iCAP TM 7400 ICP-OES with autosampler (ASX-280, CETAC Teledyne) was used. A 0.45 μm nylon filter was used to prepare water samples for dissolved metal analysis. An IDEXX® Legiolert with quanti-tray system was used to determine L. pneumophila, and trays were incubated for a week at 39°C. Locations that had less than 1 MPN/100 mL were not counted as detected. A cytoflex flow cytometer (Beckman-Coulter, Inc.) was used to determine total cell counts with method 366.1 [46]. TOC concentration was measured using Shimadzu TOC-L CPH/CPN with EPA method 415.1 [47]. A gas chromatograph/mass spectrometer system that is Agilent GC-7890B coupled with an Agilent TQ 7000C triple quadrupole MS was used to determine TTHM levels. Flushing After first draw stagnant water samples from all buildings were collected, the authors removed all water from the plumbing by first running cold water from the janitor sinks with highest flowrate. Flushing also started in the order of building C, B, and then A. Flushing was not halted until a chlorine residual concentration of 0.2 mg/L as Cl 2 was detected. While flushing, water samples were collected for chlorine and temperature analysis every minute. After flushing stopped, the authors removed and cleaned all aerators by scrubbing them with a new toothbrush and soaked them in food grade vinegar for 30 minutes. Toilets were flushed three times. All toilets near the classroom were child sized toilets (about 4.84 L per flush). After all fixtures were flushed, the authors returned to the janitor sink and flushed building hot water. Gas water heaters were subsequently drained by plumbers hired by the building owner after the authors left. The building owner also followed the author’s recommendation to operate dishwashers three times, and discard three batches of ice from the icemaker. Two weeks after the flushing (July 10th), the authors revisited the school to again collect first draw water samples. The sampling and analysis approach then was similar to the first visit except aerators were not removed or cleaned and flushing was not conducted. When the authors returned, they were informed that irrigation had continued to be conducted using an outdoor spigot from building B.

Implications and recommendations This study was conducted to better understand water quality in buildings that had been stagnated for three months and the effectiveness of flushing to improve water quality. The buildings were not initially designed for use as an elementary school and the owner (second owner of the property) did not have drawings that outlined the plumbing components (i.e., location, types, sizes, lengths, etc.). During the pandemic, the public water supplier and state health department specifically advised school building owners to flush out stagnant water [29, 64]. After three months of stagnation, first draw water samples had no detectable chlorine residual concentration and nickel and lead exceeded health-based drinking water thresholds. L. pneumophila was found at its greatest concentration in the three month stagnated cold water (188 MPN 100 mL). Fixture flushing reduced heavy metal levels below health-based drinking water limits. Flushing sometimes, but not always, resulted in water with a chlorine residual being detected at fixtures. L. pneumophila concentrations were reduced due to flushing. Though, L. pneumophila was detected at different fixture locations and lower concentrations two weeks later after the stagnant cold water flush (max. 61 MPN/100 mL). Because L. pneumophila resides in biofilms it was not surprising this organism was found in the plumbing after flushing [65–67]. Results from the present study indicate that flushing reduced L. pneumophila levels below 100 CFU/mL. This finding indicated that shock disinfection [40–42] was not needed, which the AIHA recommends when 100 CFU/mL is detected. For context, Hamilton et al. [68] recommends faucet activities present a risk at a concentration of 102 CFU/mL using annual infection risk metric for a scenario when the faucet is used 20 times per day and 30 seconds per use. Results of the present study agree with some of the existing literature but underscore several knowledge-gaps. Flushing did not always prompt disinfectant levels to be found at faucets and this may be because unchlorinated water was delivered to the building and chlorine residual decayed as water was drawn to the faucet. Better understanding the chemical and microbiological variability of water delivered to service lines is needed. Here, L. pneumophila concentrations were reduced by flushing found like others [27, 30, 32]. In contrast, others have found L. pneumophila concentrations increased after flushing [24, 32]. Flushing has previously demonstrated short-term (24 hour) benefits by reducing microbial levels at fixtures within large buildings [68]. Bench- and pilot-studies are needed to examine the impact of flushing frequency on fixture water quality. Future work should also focus on understanding the sources of L. pneumophila and conditions that cause greater L. pneumophila levels post-flushing. This will require better understanding plumbing complexity and monitoring. Culture, and qPCR methods for L. pneumophila and other organisms may provide greater insights [45]. Specificity in routine sampling and testing for metal contaminants and microorganisms for building plumbing should be developed as only general recommendations exist [69, 70]. While the present study was focused on buildings being used as an elementary school, none of the buildings were initially designed to be school buildings. Stagnation caused water quality problems are not unique to school buildings, which can be impacted by plumbing design, and low to no water use during weekends, as well as summer and winter vacations. To help lessen water quality variability at fixtures, it is recommended that each building owner create and execute a building water quality maintenance program. Here, such a program can instill the importance of plumbing safety and maintenance on building inhabitant health. This program should also including a flushing plan created using as-built drawings. The U.S. Department of Education, state regulators, and health departments could require schools include this information in their formal health and safety plans. Schools should also consider: (1) that before buildings are reopened flush water outlets to remove water with higher metal and microorganism contaminant concentrations, (2) to strive to maintain chlorine residual at fixtures to minimize biofilm growth similar to goals worked towards by public water suppliers for systems where chlorine residual is used, and (3) maintaining the water heater temperature at the highest temperature allowable by state regulation and code as well as the hot water recirculation loops, if any. A single plumbing flush was effective at reducing heavy metal concentrations, bringing in disinfected water, and reducing L. pneumophila levels to all fixtures.

Acknowledgments Special thanks are extended to Environmental Engineering Laboratory Director Dr. Nadya Zyaykina, graduate students Elizabeth Montagnino and Sruthi Dasika, undergraduate students Andrew Golden and Ryan Day.

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