Graduate Studies

 

First Advisor

Bruce Dvorak

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Civil Engineering

Date of this Version

12-5-2023

Document Type

Dissertation

Comments

Copyright 2023, Matthew James Thompson

Abstract

Wastewater treatment protects society and the environment by reducing pollutants generated from communities prior to discharge into local water bodies. Small water resource recovery facilities (WRRFs) represent the majority of centralized wastewater treatment systems, are resource intensive, and often lack resources needed to evaluate sustainability improvements. The goal of this dissertation was to identify primary sources and drivers of environmental impacts in small WRRFs and exploration of pathways to improve their environmental sustainability. Case study data collected from small WRRFs in Nebraska was analyzed using environmental life cycle assessment (LCA) to quantify the environmental impact of facilities and existing opportunities. This included comparing the use of mechanical WRRFs and lagoon systems, agriculture water reuse, energy efficiency improvements, on-site solar energy, improved design sizing, collection system rehab, and recycling. Lagoons exhibit smaller environmental impacts relative to mechanical WRRFs but use significantly more land. Construction phase impacts are larger for lagoons causing results to be sensitive to system lifespan and electric grid mix. Net positive environmental benefits were estimated for seven lagoons using treated water for agricultural with increased crop yields providing the most value. Design sizing and seasonal precipitation variations drive impacts due to coinciding effects on lagoon supply and cropland demand. Impacts are sensitive to changes in agriculture land air emissions. Data was collected for 35 site-specific energy efficiency (E2) recommendations and three on-site solar renewable energy systems. Improvements in energy efficiency (e.g., aeration control) showed the largest emission reduction per dollar invested and shortest paybacks. On-site solar systems provide the largest environmental footprint reduction while having less operational involvement, greater resiliency, and less uncertainty in terms of sustained benefit. Synthesis of six research studies that included a total of 52 WRRFs highlighted that most environmental impacts, both from embedded infrastructure and operations are effectively “locked in” during the conceptual and detailed design phase of a facility. Most notably, technology choice and detailed design decisions affect the process control capability and consequential operating resources.

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