Date of Award

5-1-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Jin Li

Abstract

Bacterial deposition in porous media is of great importance in a number of environmental processes such as bioremediation, water treatment and pathogenic contamination. Pseudomonas aeruginosa (P. aeruginosa) is a ubiquitous Gram-negative bacterium in the environment, which is able to cause disease particularly to susceptible individuals. It has been widely used as a model microorganism to study biofilm formation and Extracellular Polymeric Substances' (EPS) influences. In this work, properties of Lipopolysaccharide (LPS) mutant ÄwaaL, EPS mutants Äpel, Äpsl, Äpel/psl of P. aeruginosa PAO1, such as zeta potential, contact angle, and hydrophobicity were determined. Packed column experiments, and Quartz Crystal Microbalance with Dissipation (QCM-D) were conducted and compared with the wild-type strain under different ionic strengths to further understand the bacterial deposition mechanisms. The deposition behavior could be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory under three ionic strength conditions (3 mM, 10 mM, 100 mM in NaCl). However, the DLVO theory and XDLVO (Extended DLVO) theory fail to explain the different adhesion behaviors among the strains. It was proposed that steric force on bacterial surfaces caused by LPS significantly affects bacterial adhesion and different chemical structures of the EPS molecules contribute to bacterial adhesion differently. The QCM-D experiment was designed to explain the adhesion differences among different EPS components: alginate, Bovine Serum Albumin (BSA), humic acid and psl polysaccharide. Zeta potentials of the chemicals and quartz particles were measured at different ionic strengths and the DLVO interaction between the chemicals and quartz was plotted. BSA, owing to its positive charged amine functional group, had the largest deposition mass under all ionic strengths. Humic acid, alginate and psl polysaccharide had very similar deposition behavior at all the conditions explored. Alginate had a very unique swelling structure at 100 mM NaCl, which contributed to the largest adhesion coefficient of the pel mutant from the column experiment. In addition, the transport and adhesion of Total Coliform, Escherichia coli (E. coli) and Enterococci under different climatic conditions at Bradford Beach, Milwaukee was explored. It was found that precipitation had the most positive effect on bacterial surge at Bradford Beach among all the influencing factors such as wind direction, wind speed and temperature. Cladophora could harbor a significant amount of bacteria because it could provide shelter and nutrients to bacterial reproduction. Beach sand could filter bacteria in lake water and sustain their growth.

Download

Share

COinS