• 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 Catalogs

    Statistics

    Display statistics

    Inhibitory Impact of Nitrite on the Anaerobic Ammonium Oxidizing (Anammox) Bacteria: Inhibition Mechanisms and Strategies to Improve the Reliability of the Anammox Process as a N-Removal Technology

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_etd_13042_sip1_m.pdf
    Size:
    2.119Mb
    Format:
    PDF
    Download
    Author
    Carvajal Arroyo, Jose Maria
    Issue Date
    2013
    Keywords
    anammox
    nitrite
    wastewater treatment
    Environmental Engineering
    anaerobic
    Advisor
    Field, Jim 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
    The anaerobic oxidation of ammonium (anammox) with nitrite as electron acceptor is a microbial process that generates nitrogen gas as main final product. After being discovered in the Netherlands in the 1990s, anammox has been applied in state-of-the-art biotechnologies for the removal of N pollution from ammonium rich wastewaters. The anammox process offers significant advantages over traditional nitrification-denitrification based processes. Since anammox does not need elemental oxygen, it allows for important savings in aeration. Furthermore, due to the autotrophic nature of the bacteria, anammox does not require external addition of electron donor, often needed in systems with post-denitrification. Although the anammox bacteria have high specific activity, they are slow growing, with doubling times that can range from 10 to 25 d. Therefore, in case of a toxic event causing the death of the biomass, a long recovery period will be required to reestablish full treatment capacity. The purpose of this work is to investigate the inhibition of anammox bacteria by compounds commonly found in wastewaters, including substrates, intermediates and products of the anammox reaction. Among common wastewater constituents, sulfide was shown to be especially harmful, causing complete inhibition of anammox activity at concentrations as low as 11 mg H₂S L⁻¹. Dissolved oxygen was moderately toxic with a 50% inhibiting concentration of 2.3 and 3.8 mg L⁻¹ to granular and suspended anammox cultures, respectively. Among the various compounds involved in the anammox reaction, special attention was paid to nitrite. Numerous literature reports have indicated inhibition of anammox bacteria by its terminal electron acceptor. However to date, there is no consensus explanation as to the mechanism of nitrite inhibition nor on how the inhibition is impacted by variations in the physiological status of anammox cells. The mechanisms of anammox inhibition by nitrite were thoroughly investigated in batch and continuous experiments of this dissertation. The results of this work demonstrate that conditions hindering generation of metabolic energy have a detrimental effect on the tolerance of anammox cells to toxic levels of nitrite. The absence of ammonium during events of nitrite exposure was shown to exacerbate its toxic effect. As a result of nitrite inhibition, nitric oxide, an intermediate of the anammox reaction, accumulated in the head space of the batch experiments. Moreover, nitrite inhibition was enhanced at the lowest range of pH tested (6.4-7.2), while same nitrite concentrations caused no inhibition under mildly alkaline conditions (7.5-7.8). Although other authors have relied on the classic concept that undissociated nitrous acid is the species responsible for the inhibition, the results in this work indicate that the pH affects the inhibitory effect of nitrite, irrespective of the free nitrous acid concentration. Nitrite stress triggered an active response of the anammox bacteria, which temporarily increased their ATP content to mitigate the inhibition. Additionally, starvation of anammox microorganisms, caused during storage or by sustained underloading of bioreactors, was found to limit the capacity of the bacteria to tolerate exposure to nitrite. The results of this dissertation indicate that the tolerance of anammox bacteria to NO₂⁻ inhibition relies on limiting its accumulation in sensitive regions of the cell. Active metabolism in presence of NH₄⁺ allows for active consumption of NO₂⁻, avoiding accumulation of toxic intracellular NO₂⁻ concentrations. Furthermore, secondary active transport proteins may be used by anammox bacteria to translocate nitrite to non-sensitive compartments. Nitrite active transport relies on a proton motive force. Therefore, conditions such as low pH (below 7.4) or absence of energy sources, which may disturb the maintenance of the intracellular proton gradient, will increase the sensitivity of anammox cells to NO₂⁻ inhibition. Strategies for the operation and control of anammox bioreactors must be designed to avoid exposure of the biomass to nitrite under the absence of ammonium, low pH or after periods of starvation.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    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.