Title:
Fate and effect of quaternary ammonium compounds in biological systems

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dc.contributor.advisor Pavlostathis, Spyros G.
dc.contributor.author Tezel, Ulas en_US
dc.contributor.committeeMember Huang, Ching-Hua
dc.contributor.committeeMember Hughes, Joseph B.
dc.contributor.committeeMember Sobecky, Patricia A.
dc.contributor.committeeMember Spain, Jim C.
dc.contributor.department Civil and Environmental Engineering en_US
dc.date.accessioned 2009-06-08T19:30:11Z
dc.date.available 2009-06-08T19:30:11Z
dc.date.issued 2009-01-09 en_US
dc.description.abstract Quaternary ammonium compounds (QACs) are ubiquitous contaminants found worldwide in both engineered and natural systems. QACs are toxic to aquatic organisms and cause co-selection for antibiotic resistance, thus providing a reservoir of antibiotic-resistant bacteria, as well as antibiotic resistance genes in QAC-polluted environments. The objectives of the research presented here were to: a) systematically assess the fate and toxicity of QACs using quantitative structure-activity relationships (QSAR); b) evaluate the biotransformation potential of QACs under aerobic, anoxic and anaerobic conditions; and c) assess the potential toxicity of QACs biotransformation products. Nine QACs, belonging to three homologous groups -- monoalkonium, dialkonium and benzalkonium chlorides -- were the target QACs. The QACs critical micelle concentration (CMC) was determined. Then, the CMC was used as a descriptor to derive relationships between QAC structure and partitioning to biosolids as well as acute Microtox® toxicity. QACs with low CMCs had a relatively high adsorption affinity for biosolids and a lower toxicity than QACs with higher CMCs, which suggests that QACs that are more mobile and more (bio)available are more toxic. The biotransformation potential of benzalkonium chlorides (BAC) -- the most commonly used QACs found in engineered and natural biological systems -- under aerobic, methanogenic, nitrate reducing, and fermentative conditions was evaluated using bioenergetics and batch bioassays. The aerobic BAC biotransformation involved sequential dealkylation and debenzylation steps resulting in the formation of benzyl dimethyl amine, and dimethyl amine, respectively. The bacterial community involved in the aerobic BAC degradation was mainly composed of species belonging to the Pseudomonas genus. All QACs tested were recalcitrant under methanogenic conditions and inhibited methanogenesis at and above 25 mg QAC/L. Under nitrate reducing and fermentative conditions, BAC was transformed to alkyldimethyl amines via an abiotic reaction known as modified Hofmann degradation and a biotic reaction known as fumarate addition, respectively. Both reactions are based on a mechanism known as nucleophilic substitution. The discovery of BAC transformation by the above mentioned two reactions is the first ever report to document QAC transformation under anoxic/anaerobic conditions and delineate the transformation pathway. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/28229
dc.publisher Georgia Institute of Technology en_US
dc.subject Biotransformation en_US
dc.subject Toxicity en_US
dc.subject Biological treatment en_US
dc.subject Quaternary ammonium compounds en_US
dc.subject.lcsh Quaternary ammonium salts Environmental aspects
dc.subject.lcsh Biotransformation (Metabolism)
dc.title Fate and effect of quaternary ammonium compounds in biological systems en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Pavlostathis, Spyros G.
local.contributor.corporatename School of Civil and Environmental Engineering
local.contributor.corporatename College of Engineering
relation.isAdvisorOfPublication 4b10037e-c1df-45bc-abca-1da6d3389c46
relation.isOrgUnitOfPublication 88639fad-d3ae-4867-9e7a-7c9e6d2ecc7c
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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