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Ozone Oxidation of Emerging Contaminants in RO Concentrate and Reductive Dehalogenation of Halogenated Contaminants Using Activated Carbon-Based Electrolysis.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Ozone Oxidation of Emerging Contaminants in RO Concentrate and Reductive Dehalogenation of Halogenated Contaminants Using Activated Carbon-Based Electrolysis./
Author:	King, Jacob Feldman.
Description:	1 online resource (277 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-05, Section: A.
Contained By:	Dissertations Abstracts International84-05A.
Subject:	Metals. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29755804click for full text (PQDT)
ISBN:	9798352999806

Ozone Oxidation of Emerging Contaminants in RO Concentrate and Reductive Dehalogenation of Halogenated Contaminants Using Activated Carbon-Based Electrolysis.
King, Jacob Feldman.

Ozone Oxidation of Emerging Contaminants in RO Concentrate and Reductive Dehalogenation of Halogenated Contaminants Using Activated Carbon-Based Electrolysis. - 1 online resource (277 pages)

Source: Dissertations Abstracts International, Volume: 84-05, Section: A.

Thesis (Ph.D.)--Stanford University, 2022.

Includes bibliographical references

As society has evolved, so have the freshwater resources that provide its drinking water - and the potentially harmful chemicals within them. Potable reuse of municipal wastewater has become increasingly important to meet drinking water demand in arid regions. Full advanced treatment systems containing reverse osmosis (RO) are typically applied to remove recalcitrant chemical contaminants in conventional wastewater (e.g., home-use pesticides and chelated metals) to produce a clean permeate at ~85% water recovery. However, the remaining ~15% (RO concentrate) contains elevated concentrations of these contaminants that pose a risk to receiving water ecosystems. Meanwhile, halogenated organics populate several lists of priority pollutants. They are common groundwater contaminants (e.g., trichloroethylene) and occur during the disinfection stage of drinking water treatment (e.g., trihalomethanes). These chemicals exhibit diverse structures, complicating their removal. This dissertation therefore investigated two methods to treat evolving wastewaters: 1) Ozone to degrade contaminants of particular concern in RO concentrate (Chapter 2), and 2) Electrochemical reduction of halogenated alkanes and alkenes using GAC cathodes (Chapters 3-4).Ozone (O3) has commonly been applied for treatment of conventional wastewaters but had not been tested to treat RO concentrate. Chapter 2 therefore evaluated ozone as a treatment for RO concentrate. O3 can react with compounds or form • OH through a series of reactions with OH- and dissolved organic carbon (DOC), and previous work has grouped contaminants based on reactivities with both oxidants. This study first established that contaminants in different groups had equivalent removals in five RO concentrates as in conventional wastewaters when the same mg O3 / mg DOC dose was applied. This study then characterized contaminants of particular concern in RO concentrate (the pesticides fipronil and imidacloprid, and Ni and Cu chelates with EDTA) based on O3 and • OH reactivity and confirmed that their removals matched their reactivity group. Additional concerns that were addressed include pathogens, the fate of metals, and toxic byproduct formation. Regarding the latter, tradeoffs between contaminant removal and byproduct formation, especially bromate, need to be considered during ozone treatment.The remaining chapters (3-4) investigated a novel electrochemical reduction treatment technique that could be used to regenerate granular activated carbon (GAC) contaminated with halogenated organics. GAC is commonly used to sequester halogenated contaminants, but its disposal can be costly. Alternatively, by taking advantage of carbon's conductivity, spent GAC can be converted into a cathode to dehalogenate sorbed pollutants. Chapter 3 synthesized previous literature on dehalogenation using carbon electrodes, identifying two key research gaps: 1) Reactivity trends across diverse halogenated contaminant classes lack uniform assessment, and 2) Reactors must be expanded to treat larger water volumes. Chapter 4 therefore evaluated reductive dehalogenation of 15 halogenated alkanes and alkenes exhibiting diverse structures using GAC cathodes. This study developed quantitative structure-activity relationships (QSARs) correlating experimental first-order degradation rate constants for alkanes and alkenes with molecular descriptors associated with an outer-sphere oneelectron transfer calculated using density functional theory (DFT). For alkanes, strong correlations (r2 0.72-0.93) and predictive capabilities were observed when using standard reduction free energies in the gas phase and Marcus Theory, suggesting these models could replace the need for intensive lab experiments. On the other hand, QSAR correlations with chlorinated alkenes were opposite those of alkanes, indicating a different reaction mechanism. Nevertheless, the short (1 min to 2 h) degradation timescales and lack of halogenated organic transformation products suggest electrochemical reduction could regenerate spent GAC and should be investigated at larger scales.Overall, this dissertation demonstrates that advanced treatment processes can remove a wide variety of contaminants in a complex wastewater matrix while highlighting the importance of (by)product mitigation and the benefits of developing predictive frameworks to inform future applications of these systems.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798352999806Subjects--Topical Terms:

601053
Metals.
Index Terms--Genre/Form:

542853
Electronic books.

Ozone Oxidation of Emerging Contaminants in RO Concentrate and Reductive Dehalogenation of Halogenated Contaminants Using Activated Carbon-Based Electrolysis.
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