Over the weekend: Water stagnation and contaminant exceedances in a green office building

Abstract

The role of water stagnation (~60 hours) in a 2-story commercial office building on building water quality was studied (January to February 2020) for three weekends. Chemical and biological parameters including pH, total chlorine, metals concentrations, Legionella spp. and total cell count were analyzed to understand the differences in water quality at the building entry point, and at eleven fixtures within the building’s copper plumbing. Consistently, the total chlorine concentration decreased over the weekend (p < 0.05), was greatest at the building entry point (maximum 0.8 mg/L), and was lowest within the plumbing (maximum 0.28 mg/L). As expected, total cell count levels were much greater on Monday compared to Friday (p < 0.05) at every sampling point. Legionella spp. was found to be highest at the fixture with no use recorded during sampling. Throughout the building, copper and lead levels increased over the weekend (p < 0.05). Copper exceedances above the federal health-based drinking water limit (1.3 mg/L) were localized to four fixtures, branched from the same riser, that shared a pattern of variable use. Flushing was conducted at one location with consistent copper exceedances but 54 minutes were required to reach the public water supply. Flushing was not a viable copper remediation method as it would need to be repeated every 19 hours or require discarding more than 50 gallons before use. No prior water testing was conducted in the buildings’ life. The results suggest that water quality varies significantly over the week. This has implications for water testing plans and interpretation of data collected from buildings.

Impact of recommissioning flushing on Legionella pneumophila in a large building during the COVID-19 pandemic

“…Similarly, mean total and intact bacterial cell counts respectively reached 1.7 × 10 6 count/mL (Figure 1B) and 5.2 × 10 5 count/mL (Figure 1C) in first draw samples after the 16-week building closure and bounced back to 7.2 × 10 5 count/mL and 2.4 × 10 5 count/mL at the end of the monthly period of distal water stagnation which followed the targeted recommissioning flushing. Overall, these cell densities in first draw samples after long periods of no use in the distal parts of the building plumbing system largely exceed formerly published values after shorter stagnation times (Lipphaus et al, 2014;Zlatanović et al, 2017;Montagnino et al, 2022;Rahmatika et al, 2022). However, they are consistent with values measured in cold and hot water at taps after varying lengths of stagnation in buildings located in the same water distribution system than the sports complex sampled in the present study (Bédard et al, 2018;Dias et al, 2019).…”

Shift to remote learning degrades water quality in buildings

“…Given that Spring 2021 represented belownormal occupancy and Fall 2021 represented normal occupancy, the results in Figure 4 indicate that building occupancy and water use had a significant impact on copper concentration. The results are consistent with copper leaching from the building plumbing during periods of stagnation (Carter et al, 2019;Masters et al, 2015;Montagnino et al, 2022;Ra et al, 2020). The age of the buildings ranged from 10 to 69 years old, which is presumed to be the age of the plumbing.…”

“…The low chlorine concentrations overall in Spring 2021 (median 0.03 mg/L and interquartile range 0.04 mg/L) were consistent with the below‐normal building occupancy due to remote learning. It is well documented that low building occupancy results in reduced water use, elevated water age, and reduced chlorine concentrations (Montagnino et al, 2022; Nguyen et al, 2011; Proctor et al, 2020; Richard & Boyer, 2021; Salehi et al, 2018; Shi et al, 2022). There is a larger interquartile range (0.15 mg/L) for free chlorine concentration in Fall 2021 which is consistent with the return to in‐person learning and normal building occupancy, which resulted in increased water use and reduced water age relative to the Spring 2021 semester.…”

“…Observations like this show that chlorine levels can decrease in copper premise plumbing, especially from the point of entry to distal locations in a building. Following the same rationale for maintaining a disinfectant residual in the city distribution system, building water systems need to maintain a disinfectant residual to prevent increased microbial activity (Ji et al, 2015; Montagnino et al, 2022). For example, low levels of chlorine have been measured in first‐draw samples from building fixtures with increased levels of chlorine measured after flushing the fixture (Richard & Boyer, 2021).…”

Legionella pneumophilaoccurrence in reduced-occupancy buildings in 11 cities during the COVID-19 pandemic

“…[1][2][3][4][5] While short periods of reduced water use (e.g., nights, weekends, school breaks) are common in building plumbing, many buildings were closed or at reduced occupancy for several months during the COVID-19 pandemic. [6][7][8][9][10] Reduced water use is associated with decreased disinfectant residual levels, equilibration of hot and cold water temperatures with building temperature, and potential for increased concentrations of contaminants such as disinfection byproducts, metals, and opportunistic pathogens. [11][12][13][14][15][16][17][18][19][20][21] Legionella pneumophila, the causative agent of Legionnaires' disease and Pontiac fever, was of particular concern because its occurrence is widely assumed to be associated with low water use, [22][23][24][25][26] and disease incidence is rising around the world.…”