Subscriber access provided by Vanderbilt Libraries
Article
Development of predictive models for the degradation of halogenated disinfection byproducts during the UV/H2O2 Advanced Oxidation Process Yi-Hsueh Chuang, Kimberly M. Parker, and William A. Mitch Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b03560 • Publication Date (Web): 15 Sep 2016 Downloaded from http://pubs.acs.org on September 20, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 31
1 2 3
Environmental Science & Technology
Development of predictive models for the degradation of halogenated disinfection byproducts during the UV/H2O2 Advanced Oxidation Process
4 5 6 7
Yi-Hsueh Chuang1, Kimberly M Parker1, and William A. Mitch1*
8 9 10 11 12 13 14 15 16 17 18 19
1
Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, California 94305, United States
*Corresponding author: email:
[email protected], Phone: 650-725-9298, Fax: 650-723-7058
20
1
ACS Paragon Plus Environment
Environmental Science & Technology
21
Page 2 of 31
Abstract
22
Previous research has demonstrated that the reverse osmosis and advanced oxidation processes
23
(AOPs) used to purify municipal wastewater to potable quality have difficulty removing low
24
molecular weight halogenated disinfection byproducts (DBPs) and industrial chemicals. Because of
25
the wide range of chemical characteristics of these DBPs, this study developed methods to predict
26
their degradation within the UV/H2O2 AOP via UV direct photolysis and hydroxyl radical (•OH)
27
reaction, so that DBPs most likely to pass through the AOP could be predicted. Among 26
28
trihalomethanes, haloacetonitriles, haloacetaldehydes, halonitromethanes and haloacetamides, direct
29
photolysis rate constants (254 nm) varied by ~3 orders of magnitude, with rate constants increasing
30
with Br and I substitution. Quantum yields varied little (0.12-0.59 mol/Einstein), such that rate
31
constants were driven by the orders of magnitude variation in molar extinction coefficients. Quantum
32
chemical calculations indicated a strong correlation between molar extinction coefficients and
33
decreasing energy gaps between the highest occupied and lowest unoccupied orbitals (i.e., ELUMO –
34
EHOMO).
35
halonitromethanes, haloacetamides, and haloacetic acids with •OH measured by gamma radiolysis
36
spanned 4 orders of magnitude.
37
relationship model (Group Contribution Method) was developed which predicted •OH rate constants
38
for 5 additional halogenated compounds within a factor of 2.
39
molar extinction coefficients, quantum yields and •OH rate constants predicted experimental DBP
Rate
constants
for
37
trihalomethanes,
haloacetonitriles,
haloacetaldehydes,
Based on these rate constants, a quantitative structure-reactivity
A kinetics model combining the
2
ACS Paragon Plus Environment
Page 3 of 31
Environmental Science & Technology
40
loss in a lab-scale UV/H2O2 AOP well. Highlighting the difficulty associated with degrading these
41
DBPs, at the 500-1000 mJ/cm2 UV fluence applied in potable reuse trains, 50% removal would be
42
achieved generally only for compounds with several –Br or –I substituents, mostly due to higher
43
molar extinction coefficients.
44 45
Introduction
46
Increasing numbers of utilities are considering municipal wastewater effluents as a secure and
47
local supply for potable water after advanced treatment.1,2 Potable reuse facilities frequently employ
48
Full Advanced Treatment (FAT) trains to remove the organic contaminants occurring in wastewater
49
effluents. FAT trains consist of microfiltration (MF), reverse osmosis (RO), and the UV/hydrogen
50
peroxide (H2O2) advanced oxidation process (AOP). Within the FAT train, the RO treatment
51
represents a broad-screen physical barrier, and the AOP represents a broad-screen chemical barrier.
52
Among organic contaminants, a report by the National Research Council on wastewater reuse2
53
indicated that concentrations of disinfection byproducts (DBPs) in reuse waters are orders of
54
magnitude closer to levels of potential human health concern than are pharmaceuticals and personal
55
care products. While low levels of regulated and unregulated DBPs occur in secondary municipal
56
effluents, ozone and/or chloramines applied upstream of microfiltration to control biofouling
57
increase their concentrations by a factor of 3 or greater in the microfiltration effluent.3 Episodic
58
discharges of industrial compounds to sewers (e.g., solvents such as methylene chloride), also may 3
ACS Paragon Plus Environment
Environmental Science & Technology
59
Page 4 of 31
represent concerns.
60
RO is capable of removing a broad suite of pharmaceuticals,4 perfluorinated compounds,5 and
61
endocrine disrupting compounds (e.g., bisphenol A).6 Although RO exhibits efficient removal (i.e.,
62
high rejection) of charged compounds, rejection rates decline with molecular weight for uncharged
63
compounds with
