Title page for ETD etd-09112008-165531

Type of Document

Dissertation

Author

Baeza, Ana Carolina ,

URN

etd-09112008-165531

Title

Removal of Pharmaceutical and Endocrine Disrupting Chemicals by Sequential Photochemical and Biological Oxidation Processes.

Degree

PhD

Graduate Program

Civil Engineering

Advisory Committee

Advisor Name	Title
Detlef Knappe	Committee Chair
David Ollis	Committee Member
Francis L. de los Reyes	Committee Member
Joel Ducoste	Committee Member

Keywords

UV/H2O2
antimicrobial activity
hydroxyl radical
pharmaceuticals
photolysis
biochemically active compounds

Date of Defense

2008-09-09

Availability

unrestricted

Abstract

The presence of biochemically active compounds (BACs) such as endocrine
disrupting chemicals (EDCs) and antimicrobial compounds in the aquatic environment
is an issue of great concern. For example, EDCs can cause gender bending in aquatic
life, and antimicrobial compounds may lead to the evolution of antimicrobial resistant
bacteria. The principal objective of this research was to quantify the effectiveness of
combining UV/H2O2 and biological oxidation processes for the mineralization of
BACs that commonly occur at trace levels in municipal wastewater and in drinking
water sources.
Initially, the photolysis and UV/H2O2 photooxidation rates of six BACs [the
antimicrobial compounds sulfamethoxazole (SMX), sulfamethazine (SMZ),
sulfadiazine (SDZ), and trimethoprim (TMP), the EDC bisphenol-A (BPA), and the
analgesic diclofenac (DCL)] were determined. Experiments were conducted in
ultrapure water, lake water (Lake Wheeler, NC) and wastewater treatment plant
effluent (North Cary Water Reclamation Facility, Cary, NC). Photolysis and UV/H2O2
oxidation rates of BACs were quantified with a quasi-collimated beam (QCB)
apparatus equipped with low pressure UV lamps, and the effects of the following
factors on the BAC oxidation rates were evaluated: (1) pH, (2) H2O2 concentration,
and (3) presence/absence of background organic matter. With the QCB apparatus,
parameters such as quantum yields and second order rate constants describing the
reaction between hydroxyl radicals and BACs were determined. With these parameters
the level of BAC transformation at different UV fluences and H2O2 concentrations
was predicted. For example, at treatment conditions used at a full-scale UV/H2O2 plant
in the Netherlands (UV fluence = 540 mJ cm-2, H2O2 dose = 6 mg L-1), the following
BAC transformation percentages would be obtained in NC lake water: ∼98% for
DCL, ∼79% for SMX, ∼60% for SMZ, ∼51% for SDZ, ∼43% for TMP, and ∼46% for
BPA. In wastewater treatment plant effluent, predicted BAC transformation
percentages were lower at the same treatment conditions because hydroxyl radical
scavengers were present at higher concentrations.
Apart from determining parent compound removal rates in UV photolysis and
UV/H2O2 photooxidation processes, antimicrobial activity removal was quantified by
conducting growth inhibition assays. Using the Enterobacteriaceae organism E. coli
ATCC® 25922, growth inhibition assay data showed that the antimicrobial activity in
photochemically treated water samples was principally a result of the parent
compound concentration that remained upon treatment. Therefore, no measurable
antimicrobial activity was exerted by the photolysis and UV/H2O2 oxidation products
of the studied sulfonamides and TMP. These results were consistently obtained for the
different background water matrices and solution pH values that were studied.
Finally, the mineralization potential of three 14C-labeled BACs (sulfadiazine,
bisphenol-A, and diclofenac) after UV/H2O2 treatment was examined with a
consortium of lake water bacteria and with bacteria associated with lake sediments.
Upon UV/H2O2 oxidation, mineralization of 14C-labeled BAC oxidation intermediates
by lake water bacteria was extremely slow (<1.1% for SDZ, <0.8% for BPA and
<0.8% for DCL in 30 days). The use of lake sediments enhanced the biodegradation
rate of sulfadiazine and its UV/H2O2 oxidation intermediates, but mineralization rates
were still slow (1.1% for SDZ and 5.2% for SDZ UV/H2O2 oxidation intermediates
after 30 days).
Overall, the results of this research suggest that the UV/H2O2 process is able to
remove BAC parent compounds and, for antibiotics, antimicrobial activity; however,
oxidation intermediates may be persistent in the environment. Additional studies
should be performed to determine the effects of these intermediates on aquatic life and
their toxicological importance in the context of direct or indirect potable water reuse.

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