• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    The role of redox mediators on the anaerobic degradation of chlorinated solvents

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_td_3158098_sip1_m.pdf
    Size:
    4.053Mb
    Format:
    PDF
    Download
    Author
    Guerrero-Barajas, Claudia
    Issue Date
    2004
    Keywords
    Biology, Microbiology.
    Engineering, Environmental.
    Advisor
    Field, James A.
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Chlorinated solvents are pollutants found frequently in the environment. Whereas lower chlorinated solvents are easily degraded under aerobic conditions, degradation of higher chlorinated solvents is favored under anaerobic conditions. It is known that some compounds can act as redox mediators assisting the electron exchange required for the anaerobic dechlorination reactions to occur. Redox mediators are compounds that can assist the anaerobic dechlorination reactions either abiotically or biologically by accelerating the degradation rates. The objective of this study is to evaluate the role of different redox mediators on the anaerobic degradation of higher chlorinated solvents such as chloroform (CF), carbon tetrachloride (CT) and perchloroethylene (PCE). The redox mediators studied are vitamin B12 (cyanocobalamin CNB12-hydroxocobalamin HOB12), riboflavin (RF) and a model of humic compound anthraquinone-2,6-disulfonate (AQDS). The study includes abiotic and biological redox mediated dechlorination. The biological studies involve two varieties of unadapted methanogenic sludge. The results obtained demonstrate that redox mediators greatly enhance the degradation rates of CF and CT when utilized at substoichiometric molar ratios. At the same time, the results also highlight the importance of the role of the microorganisms during the dechlorination process. Vitamin B12 and riboflavin presented larger impact than AQDS on the degradation rates of CF and CT. Since vitamin B12 had the highest positive impact on the biodegradation rates of CF and CT, an attempt was done to stimulate its biosynthesis by the methanogenic sludge during the CT dechlorination. The approach used to promote the biosynthesis of vitamin B12 involved different vitamin B12 precursors such as porphobilinogen, and some primary substrates such as methanol and 1,2-propanediol. The results obtained show that the formation of the corrin ring may be the limiting step during vitamin B12 biosynthesis. One carbon substrates such as methanol, combined with porphobilinogen had a positive impact on the biodegradation rates of CT. The study suggests that the combination of methanol and vitamin B12 precursors could be a good alternative to stimulate the vitamin B12 biosynthesis by methanogens and therefore, the enhancement of the biodegradation rates of chlorinated solvents. This study presents the lowest molar ratio of vitamins that enhanced the dechlorination rates reported so far for biodegradation of chlorinated solvents involving methanogens. Also, this is the first report on the use of riboflavin as a redox mediator during dechlorination processes.
    Type
    text
    Dissertation-Reproduction (electronic)
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Chemical and Environmental Engineering
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.