Graduation Year

2026

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Kebreab Ghebremichael, Ph.D.

Committee Member

James Mihelcic, Ph.D.

Committee Member

Tirusew Asefa, Ph.D.

Committee Member

Nancy Diaz-Elsayed, Ph.D.

Committee Member

Rebecca Zarger, Ph.D.

Keywords

Climate Change, Decision Making, One Water, Sustainability, System Dynamics

Abstract

Water and wastewater utility management is becoming increasingly complex due to factors like urbanization, climate change, new regulations, and rising costs. Utility leaders must balance competing political and financial pressures while managing aging infrastructure, rising demand, climate resilience planning, and customer concerns about affordability. Reuse of treated wastewater has emerged as a promising solution to address scarcity, declining source water quality, and new regulations on wastewater discharge in the United States. However, water reuse is not one-size-fits-all, and bespoke solutions are needed to optimize economic, environmental, and social returns from this finite resource. Despite growing interest, little is known about the unique resilience requirements of water reuse systems, especially in smaller communities serving less than 1 million people and in coastal, subtropical regions–possibly due to the misconception that such areas are not water scarce.

To improve the scientific understanding of resilience-oriented urban water management, this research explores utility decision-making and system dynamics in the Tampa Bay region of Florida. This rapidly growing coastal region is highly exposed to climate risks like changing rainfall patterns, sea level rise, and extreme weather. Statewide regulations have also limited the non-beneficial disposal of treated wastewater, driving interest in water reuse. A regional survey and two System Dynamics case studies were conducted to provide a holistic picture of perceived threats, decision pressures, and resilience strategies at water utilities across the Tampa Bay area. First, utility leaders across the region were surveyed to identify decision-making pressures, perceived threats to resilience, and adaptation strategies. Next, System Dynamics models were constructed with two local utilities to explore how water reuse systems can meet future demand and advance social, financial, and environmental goals under uncertainty. This modeling framework is well-suited to evaluating technical, economic, and environmental tradeoffs while capturing feedbacks between conventional and reclaimed water systems.

Survey results from 19 different public utilities across the Tampa Bay region highlighted the importance of addressing demand growth while balancing political and financial decision-making pressures. Utility leaders indicated that affordability and the provision of wastewater services could be difficult to ensure in the future. To cope with supply limitations and regulations on treated wastewater discharge, many of the surveyed utilities are considering or currently implementing water reuse projects. However, adaptation strategies were frequently traditional and cost-sensitive, suggesting that there may be sociopolitical barriers to innovative, interdepartmental solutions.

In Plant City, dynamic optimization revealed tradeoffs between potable reuse and public access reclaimed water (e.g., for residential irrigation and commercial use). Allocating reclaimed water to both direct and indirect potable reuse at design capacity was not feasible while fully meeting public access demand. When public access fulfillment was not explicitly prioritized, optimal strategies favored potable reuse, yielding higher net revenues and lower groundwater withdrawals. Key variables influencing the attractiveness of direct potable reuse included population and demand growth, treatment losses, indoor water use, and the degree to which unmet reclaimed water demand shifts to potable demand.

In Dunedin, climate-sensitive modeling examined how temperature and rainfall affect reclaimed water operations. Warming temperatures and shifting rainfall patterns may increase reclaimed water utilization, but could intensify extreme weather risks, particularly in September and October. Tipping points were identified wherein compound weather events could lead to sanitary sewer overflows. Upstream flow control (cure-in-place pipe lining) for the collections system showed promise for reducing overall and peak inflows as well as improving utilization of reclaimed water. However, for public access systems, an additional beneficial end use that accepts variable seasonal flow appears necessary to completely eliminate surface water discharge. Water reuse planning should account for climate and weather vulnerabilities using dynamic, systems-based analysis to evaluate seasonal supply and demand variation.

Overall, findings of this research suggest that water utilities in the Tampa Bay region face strong sociopolitical and financial pressures that could influence their decisions when addressing supply and demand challenges. Public access reclaimed water systems may be the most familiar water reuse practice, but innovative potable reuse options may better serve economic and environmental goals. Interdepartmental and inter-utility coordination is recommended to explore optimal wastewater end-uses with multiple benefits for aquifer recharge, flood resilience, and public recreation. For utilities with existing reclamation systems, upstream flow controls could reduce inflows and the risk of sanitary sewer overflows while improving utilization, but should be paired with another appropriate end use to achieve full regulatory and sustainability goals. This research contributes to a growing body of systems thinking and systems-based scientific research around the implementation of water reuse and One Water initiatives, advancing Sustainable Development Goals #6 and #11: Clean Water and Sanitation and Sustainable Cities and Communities.

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