Stagnation Impacts on Building Drinking Water Safety: The Pandemic and Microplastics

The pandemic prompted buildings globally to transition to low or no occupancy as social distancing to reduce the spread of Coronavirus Disease (COVID-19). This consequence prompted concerns about the chemical and microbiological safety of building drinking water due to stagnation. At the same time, microplastic (MP) pollution received increasing global attention due to their presence in the environment and recent discoveries within water distribution systems and at building faucets. MP sources have primarily been targeted as originating within the drinking water sources, but plastic plumbing components are less discussed and known to deteriorate into fragments and smaller pieces that reach faucets. Literature at the time of this work as sparse on stagnation impacts to drinking water quality and the fate of MPs in plumbing. In particular, health officials and building owners issued and received many differed guidance documents telling building owners do different things and no standard guideline was available to reduce the health risks caused by stagnant building drinking water. This dissertation  examined three different types of buildings during closed to low water use conditions and conducted bench-scale testing to explore the phenomena observed in the field. Chapter 1 describes water quality impacts during a 7 year old ‘green’ middle school as it transitioned from Summer (low water use) to Fall (normal use). Field experiments revealed that more than half of first draw water samples exceeded the copper (acute) health-based action limit during low water use. Copper concentration within the school increased as distance from building entry point increased. Chapter 2 and 3 describe report on chemical and microbiological water quality in buildings at a university buildings (Chapter 2), and elementary school (Chapter 3). Chapters 2 and 3 revealed that stagnation negatively impacted chemical and microbiological building water quality (cold and hot) but flushing was effective at remediating high concentration of heavy metals and Legionella pneumophila at most locations. But in large buildings, where building plumbing system was more complicated, flushing did not always result in improved water quality. Also discovered was that water quality again deteriorated even after whole building water system was flushed. It is important to understand own building systems to maintain water quality as each building complexity requires specific knowledge and solutions. Chapter 4 describes current knowledge associated with MPs in drinking water and results of bench scale experiments on MP fate and transport in building plumbing. This work identified that while MPs have been reported at building faucets, sampling details lacking from available studies often resulted in study results not being comparable across others. Based on the review of the issue, it was found that MPs have likely reached building faucets for decades but have received no characterization until recently. Bench-scale testing using two MPs, of different density, in copper and crosslinked polyethylene (PEX) pipes revealed size influenced the amount of MPs retained in a pipe. Research needs were identified to determine the fundamental factors that control MP fate in plumbing and their presence at building faucets.