Sensing Drinking Water: Towards Real-Time Technology to Monitor, Control, and Study Drinking Water Quality at the Tap

Abstract

A new generation of drinking water management tools that incorporate real-time sensing and data-driven control stand to transform our interactions with drinking water systems in a more comprehensive way. Sensors have been lauded for their promise to revolutionize drinking water management, but the adoption of real-time data technologies lags behind other infrastructure sectors and their value as a tool in the management of drinking water systems is still unknown. Using low-cost sensors, programmable microcontrollers, and wireless communications, this work introduces a suite of next-generation tools to monitor drinking water quality throughout distribution systems and building plumbing in real-time. To advance the goal of adopting sensor networks for drinking water distribution systems, this work first introduces a novel open-source, end-to-end wireless platform for the real-time monitoring of drinking water systems capable of measuring pH, oxidation-reduction potential, electroconductivity, temperature, and pressure. Second, the applications and value of these tools are evaluated in three unprecedented real-world deployments in Ann Arbor and Ypsilanti, Michigan, USA and in Mexico City, Mexico with a total cumulative 34 sites – resulting in the largest deployment effort of a wireless sensor network to measure drinking water quality directly in residential taps. In each of these deployments, we demonstrate the detection of phenomena that would have been missed through existing, low-throughput monitoring approaches. The deployment in Ann Arbor emphasizes the importance of real-time measurements in a drinking water distribution system, highlighting shifts in neighborhood-scale electroconductivity (a proxy for total dissolved solids) that would have been missed as part of established sampling procedures. The deployment in Ypsilanti actively measured with ORP the decay of free chlorine after overnight stagnation in building plumbing. The Mexico City deployment demonstrates highly variable water quality and supply in intermittent systems and characterizes the variability of chlorine concentrations between continuous and intermittent portions of the city. Manual flushing of building plumbing is commonly used to address water quality issues that arise from water stagnation. Autonomous flushing informed by sensors has the potential to aid in the management of building plumbing. To further our understanding of water quality in building plumbing and develop smart flushing practices, an experiment was designed to flush the tap twice per day in buildings with free chlorine (Ypsilanti) and chloramine (Ann Arbor). The overnight decrease in ORP measured in Ypsilanti was not observed when tap water was automatically flushed. Results from the experiment also show that a “smart” flushing protocol could be informed by temperature signals to detect when flushing is done, potentially leading to water savings. Lastly, sensor nodes are used to better understand the spectrum of intermittent water supply and its impacts on the experience of water quality. This study goes beyond the technology application by using a combination of anthropology and statistical methods to understand the effects of intermittent water supply on public health at the household level. The analysis demonstrates that dynamics in water supply and water quality are key factors in shaping people’s water quality experience. As we embark on unprecedented water challenges around the world, including natural and anthropogenic pressures in water resources, real-time water quality monitoring systems should be considered as part of a new generation of information-driven infrastructure to support drinking water management and research as shown in this dissertation.