Civil Engineering ETDs

Publication Date

Fall 11-13-2019

Abstract

Interactions between bacteria and surfaces during the initiation of biofilm formation are complex phenomena with significant and wide-ranging implications for nutrient cycling, ecosystem and human health, and the remediation of anthropogenic pollutants. Nitrifying biofilms are currently used for ammonia removal in wastewater treatment plant (WWTP) systems. As well-studied biofilms, they can serve as models towards understanding crucial aspects of biofilm engineering. The overall objective of this research was to better understand how variations in specific surface chemistries and topographical features affect nitrification rates and microbial populations in an effort to develop technologies for improved productivity. The experimental approach was to run a series of laboratory scale studies where nitrifying biofilms were developed on surfaces that varied in terms of their chemical composition and/or roughness parameters. In experiment 1, nylon and activated carbon surfaces were evaluated to determine the impacts of roughness on a micro- and millimeter scale. Experiment 2 studied the effects of positive and negative skewness of silicone surfaces compared to a flat silicone control. Finally, experiment 3 assessed the influence of modified poly-dimethylsiloxane (PDMS) featuring charged and uncharged hydrophilic surface chemistries compared to unmodified hydrophobic PDMS material. These surface characteristics were varied to study their effects on the attachment, growth, cohesion, and nitrification rates of nitrifying biofilms. Hydrodynamic flow conditions were both calculated and modeled by computational flow dynamics (CFD), and aeration and discrete nitrogen-loading were imposed on the biofilms in sequencing batch reactors (exp. 1) and continuous-flow annular bioreactors (exp. 2 and 3). In each experiment, nitrification performance was measured. Biofilm samples were collected, and their communities were identified by DNA sequencing to classify populations and calculate diversity. Principal component analysis (PCA) was used to track the evolution of microbial populations, to isolate effects from surface characteristics from those of shared growth conditions, and to link nitrification performance to members of the biofilm community. Results from these experiments provide guidance as to how surfaces can be tailored to improve initial bacterial adhesion, biofilm development, and improve knowledge of temporal community shifts within complex communities.

Keywords

Biofilm, Physiochemical Surface Modification, Nitrification, Remediation, Annular Bioreactors, Surface Chemistry

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Dr. Andrew J. Schuler

Second Committee Member

Dr. Bruce M. Thomson

Third Committee Member

Dr. Jose M. Cerrato

Fourth Committee Member

Dr. Nichlaus J. Carroll

Available for download on Tuesday, December 14, 2021

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