Distributed reuse and water supply: Unconventional approaches enable sustainable urban water systems
Tackling water and wastewater infrastructure challenges require unconventional solutions. Implementing direct potable reuse in a distributed water supply system may yield financially competitive and energy efficient strategies that enhance urban water sustainability.
Modern water and wastewater treatment is one of the top 10 greatest engineering achievements in the 20th century. For years, we have enjoyed the benefits of clean and safe water provided by centralized water supply systems, many of which are at least half a century old. Parallel to this success, water infrastructure in the United States is grappling with unprecedented challenges: increasing demand due to a growing urban population, aging pipelines, deteriorating water quality, lack of investment for upkeep and modernization, and on top of these, climate change. The scale, severity, and technical and operational complexity of these daunting water infrastructure challenges require unconventional solutions, which provide a great opportunity to re-evaluate our water infrastructure and develop resilient and sustainable water management strategies. Mega-cities in developing countries that are still establishing their urban water supply systems, can also benefit from a new generation of system designs.
We have been fascinated by the idea of a hybrid water supply system that integrates alternative water sources such as reclaimed storm water and wastewater to supplement conventional water supply. Despite the many discussions on this idea, quantitative comparisons with the conventional approach are rare. We value the importance of analytical predictive tools, so we develop them to analyze and understand urban water systems of various configurations and assess the energy, economic and environmental impact of implementing such novel hybrid systems (Figure 1). This effort received tremendous support from our long-term partner, the City of Houston’s Department of Public Works, who generously provided us with information of the City’s water and wastewater system, making this study the first on a water supply system of a major city also facing various sustainability and resilience challenges.
Our paper is the first of a series of studies that quantitatively explores distributed water supply as a potential solution to some major water infrastructure challenges. The hybrid system considered in this study collects and treats wastewater to drinking water quality at multiple wastewater treatment plants located throughout the city, and uses the reclaimed water to supplement the city’s water supply from conventional centralized water treatment plants. We try to answer questions such as: What is the value of distributed water system via water reuse as a strategy to improve water and energy efficiency? How resilient is a centralized vs. a hybrid water system to disruptive weather events? What is the role of emerging technologies in enhancing infrastructure resiliency? And so on. One of the interesting findings was that properly designed system configurations attain system-wide net energy savings even with the high energy consumption of existing technologies used for advanced treatment of wastewater.
We are pleased with the opportunity to share insights on resilient urban water infrastructure in the context of global climate change and regional/local socioeconomic dynamics. We hope the tools we have developed, and continue to develop, will support data-driven policy making and promote much needed technological development and implementation to improve water supply for future generations.