Award Date

5-1-2020

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Civil and Environmental Engineering and Construction

First Committee Member

Jacimaria Batista

Second Committee Member

Erica Marti

Third Committee Member

Daniel Gerrity

Fourth Committee Member

Boo Shan Tseng

Number of Pages

434

Abstract

Perchlorate is a chemically stable anion which was used as an oxidizer in rocket propellant and explosives throughout the 1950’s and 1960’s. While natural sources of perchlorate exist, perchlorate in the environment is primarily a result of contamination from anthropogenic processes. Perchlorate contamination has now been identified in at least 45 states and is hazard to human health due to perchlorate’s ability to interfere with uptake of iodine in the thyroid gland. One of the most common and cost effective treatment methods for perchlorate remediation is biological reduction—utilizing bacteria to enzymatically reduce perchlorate into chloride and oxygen.

The purpose of this bench-scale laboratory investigation was to identify the factors preventing and amendments required to promote biodegradation of hexavalent chromium, nitrate, chlorate, and perchlorate in a highly contaminated site with a history of ammonium perchlorate production. There is a lack of research into perchlorate reduction in adverse conditions including those with high initial perchlorate concentration (>100 mg/L), high salinity (>1% NaCl), and multiple co-contaminants.

Microcosm experimentation revealed hexavalent chromium presence, high levels of dissolved solids, and a lack of available carbon source to be the primary factors preventing biodegradation. Of the four carbon sources tested, food-grade blackstrap molasses was found to be the most effective due in part to its ability to abiotically reduce the hexavalent chromium. Bioaugmentation was required when utilizing sodium acetate as the selected carbon source, but further research is required to assess whether bioaugmentation is necessary for molasses-fed microcosms. Predominant bacterial genera identified in samples with successful hexavalent chromium, nitrate, chlorate, and perchlorate reduction included Vibrio, Azoarcus, Pseudomonas, and Denitrobacter.

Keywords

Biological remediation; Bioremediation; Chlorate; High salinity; Perchlorate

Disciplines

Environmental Engineering

File Format

pdf

File Size

24.3 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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