Civil Engineering ETDs

Publication Date

Summer 7-28-2026

Abstract

This dissertation combines meta-omics, microbial ecology, and hydrodynamic analysis to explore mechanisms of enhanced biological phosphorus removal (EBPR) and aerobic granular sludge (AGS) in municipal wastewater treatment. Metagenomic and functional gene profiling of a laboratory sequencing batch reactor fed with amino acids and proteins, and with a low abundance of known polyphosphate-accumulating organisms (PAOs), revealed abundant Herpetosiphonaceae and Dermatophilaceae families possessed key PAO metabolic traits, including phosphate scavenging, anaerobic carbon pathways, and ppk2 gene variants aligned with established PAOs. These findings suggest amino acid-driven EBPR can occur via previously unrecognized taxa, challenging current engineering assumptions and highlighting the need for updated design criteria for full-scale water resource recovery facilities operating under high organic nitrogen loading or using endogenously derived carbon. Particle image velocimetry (PIV) and computational fluid dynamics (CFD) modeling characterized turbulence in a lab-scale complete-mix reactor with different impeller sizes and rotation rates. All configurations generated fully turbulent, strain-dominated flow, but larger impellers caused localized high-turbulence zones with increased shear and collision potential, possibly affecting granule development. Smaller impellers produced more uniform, lower intensity turbulence, even at higher rotation rates, suggesting they may favor granulation. Length scale analyses indicated granules fall within the dissipative subrange, implying hydrodynamic forces set constraints on granule size and stability. By integrating microbial ecology, metabolic pathways, and hydrodynamics, this work offers insights into amino acid fed EBPR mechanisms and turbulence-driven granulation, guiding the design and optimization of water resource recovery facilities for EBPR and AGS.To assess the impact of mixer designs on the potential for sludge granulation, detailed particle image velocimetry (PIV) and computational fluid dynamics (CFD) modeling characterized the turbulence in a laboratory-scale complete-mix reactor with different impeller sizes and rotation rates. All configurations produced full turbulent, strain-dominated flow, but the large impeller generated more localized, high turbulence regions, creating concentrated zones of both fluid shear stress and particle collision potential that could affect granule development. In contrast, the small impeller produced more uniform turbulence with lower intensity turbulence even though it was operated at a higher rotation rate than the large impeller, which may indicate that smaller, faster rotating mixers may produce conditions more favorable for granulation. Taylor and Kolmogorov length scale analysis showed that granules consistently fall within the dissipative subrange, suggesting that hydrodynamic forces are likely to fundamentally constrain granule size and stability. By integrating microbial ecology, metabolic pathway characterization, and hydrodynamic perspectives, this work provides new insights into both amino acid-fed EBPR mechanisms and the turbulence drive-processes that may govern granulation, providing practical guidance for designing and optimizing WRRFs for EBPR and AGS.

Keywords

Enhanced biological phosphorus removal (EBPR), Aerobic Granular Sludge (AGS), Amino Acid and Protein EBPR, Turbulence Characterization, Mixing Design, Metagenomic Profiling

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Andrew Schuler

Second Committee Member

Svetlana Poroseva

Third Committee Member

Jose Cerrato Corrales

Fourth Committee Member

Anjali Mulchandani

Fifth Committee Member

Jeremy Edwards

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