Physical, Chemical, and Microbiological Water Quality Variation between City and Building and within Multistory Building

Abstract

Municipal drinking water entering buildings can experience degraded water quality due to in-building water treatment devices, plumbing design, materials, and occupancy patterns. To understand water quality patterns, we installed online sensors and collected grab samples throughout a multistory university building to quantify temporal and spatial fluctuations in temperature, pH, free chlorine, dissolved copper, trihalomethanes (THMs), cellular adenosine triphosphate (cATP), and organic matter surrogate (UV254). A whole-building water softener had a detrimental impact on water quality, increasing pH, decreasing disinfectant residual, and increasing THMs. Disinfectant residual was always greatest at the building inlet, with little to no measurable free chlorine at sinks and water fountains. Cellular adenosine triphosphate levels were lowest at the building inlet and measured greater at water fountains. Copper levels were <0.2 mg/L entering the building but ranged from 0.5 to 1.5 mg/L within the building. HVAC operations resulted in less variability for in-building water temperature than at the water treatment plant with temperatures averaging 5 °C warmer inside the building than at the building inlet. Trihalomethane concentrations were influenced by chlorine residual, pH, and water demand, with consistently higher in-building measurements than at the building inlet. Trihalomethane speciation remained constant throughout the study with chloroform being the greatest contributor to speciation, followed by dichlorobromoform, dibromochloromethane, and finally bromoform.

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

“…Building AZ-1 (Legiolert positivity: 100% [n=7 of 7]; qPCR positivity: 100% [n=7 of 7]) is a green building (LEED-certified); LEED-certified buildings have previously been linked to high water residence times and, in certain cases, L. pneumophila occurrence. 12,65,66 In addition, AZ-1 uses whole-building water softening upon entry of water into the building. A sample collected from a water storage tank immediately after the water softener was positive for L. pneumophila by both Legiolert (10,616 MPN/L) and qPCR (650 gc/L) and had a low chlorine residual (0.05 mg/L as Cl 2 ), indicating that residual disinfectant loss was occurring in the water softener.…”

“…Previous investigations in this building found that the softener was oversized for the building water demand, leading to high water residence time in the softener. 65,66 Building PA-1 (Legiolert positivity: 94% [n=17 of 18]; ddPCR positivity: 67% [n=12 of 18]) is a laboratory-scale experimental shower rig consisting of three water heaters, each of which supplies three showers. The water heaters were operated at 49°C and thermostatic mixing valves limited water temperature to 40°C at the fixtures.…”

“…Previous investigations in this building found that the softener was oversized for the building water demand, leading to high water residence time in the softener. 65,66 Building PA-1 (Legiolert positivity: 94% ) is a sports building with a complex hot water system, which includes four water heaters in series. Issues identified included that a portion of the returned hot water was mixed with the hot water exiting the water heaters, resulting in a decrease of the distributed hot water temperature to below 60°C; a single thermostatic mixing valve for many showerheads (>20) created large volumes of tepid water; and the third water heater was found to be off but still connected to the system, resulting in cooling of hot water to 30°C.…”

Pre‐ and post‐flushing of three schools in Arizona due to COVID‐19 shutdown

“…Other authors have also shown that disinfectant decay in pipe is unavoidable save for glass pipes which is not a suitable premise plumbing material (Nguyen et al, 2012 ; Tolofari et al, 2020 ; Zhang et al, 2017 ). Studies have also shown an increase in THM formation in buildings due to stagnation (Dion‐Fortier et al, 2009 ; Salehi et al, 2020 ) or equipment such as hot water tanks (Dion‐Fortier et al, 2009 ) and water softeners (Richard et al, 2021 ). Leaching of copper into water is undesirable as high levels of copper during short‐term exposure can cause stomach issues while long‐term exposure can cause neurological issues and liver and kidney damage (U.S. Environmental Protection Agency, 2020b ).…”

“…The biofilm of premise plumbing materials has been shown to be a reservoir for L. pneumophila and Pseudomonas aeruginosa , two common OPPPs (Moritz et al, 2010 ). And building equipment, such as water softeners (Richard et al, 2021 ) and hot water tanks (Rhoads et al, 2015 ) can also promote microorganism growth. Lautenschlager et al ( 2010 ) and Bédard et al ( 2018 ) were able to demonstrate that flushing showed a decrease in viable cell count for cold water after varying stagnation events (1 h to 10 days) (Bédard et al, 2018 ; Lautenschlager et al, 2010 ).…”