Publication Date

2019-04-25

Availability

Open access

Embargo Period

2019-04-24

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Civil, Architectural and Environmental Engineering (Engineering)

Date of Defense

2019-01-24

First Committee Member

Sung Hee Joo

Second Committee Member

James Douglas Englehardt

Third Committee Member

Helena Solo-Gabriele

Fourth Committee Member

Naresh Kumar

Abstract

Recently, the presence of antibiotic-resistant bacteria in water is a major concern worldwide due to its adverse health effects. Conventional disinfection technologies, such as ultraviolet, ozone, and chlorine disinfection are currently used to inactivate antibiotic-resistant bacteria in water. Conventional disinfection technologies not only produce byproducts but also selectively promote the survival of antibiotic-resistant bacteria. Nanoparticles (NPs), even in a small amounts, have potential benefits as novel materials in terms of inactivating pathogenic bacteria due to their strong antibacterial effect. However, because of issues pertaining to leaching, mobility, and the cost of NPs, their applications for water treatment have not been pursued earlier. Therefore, this study seeks to understand the development of NPs for water treatment applications by using alginate coating to encapsulate NPs. To study the development of NP-alginate beads, the antibacterial properties and toxicity mechanisms of different types of NPs (i.e., Industrial NPs, NPs derived from consumer products, and nanohybrids) were investigated on antibiotic-resistant bacteria (i.e., E. coli and P. aeruginosa). The study showed that the large surface area and dispersion of NPs enhanced the effect of antibacterial properties. ROS (reactive oxygen species) produced by NPs was the primary mechanism for inactivating the antibiotic-resistant bacteria. Based on the results of the effects of antibacterial properties and the mechanisms of NPs, novel nanocomposites for the removal of antibiotic-resistant bacteria in water were synthesized by encapsulating NPs in alginate-beads. NP-alginate beads were designed to prevent NP’s leaching into the water, and to promote the antibacterial properties of NPs through dispersion and increased surface areas. The results showed that the NP-alginate beads inactivated up to 99.1% of antibiotic-resistant bacteria and the bacterial inactivation increased with the increasing dose of NPs. In the current study, these NPs-alginate beads revealed efficacy with no by-product formed and proved cost-effective with just a small amount of NPs and are reusable in the treatment of antibiotic-resistant bacteria in water. Therefore, the alginate nanocomposites can be deemed as potential antimicrobial agents for water disinfection, and offer a new opportunity for a large-scale production for point-of-use treatment.

Keywords

Antibacterial effect; Antibiotic-resistant bacteria; Nanoparticles; Toxicity mechanisms; Zinc oxide

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