Degradation and changes in toxicity and biodegradability
of tetracycline during ozone/ultraviolet-based advanced
oxidation
Huyen Trang Luu and Kisay Lee
ABSTRACT
Advanced oxidation processes (AOPs) composed of O
3
,H
2
O
2
and ultraviolet (UV) were applied to
degrade tetracycline (TC). Degradation efficiency was evaluated in terms of changes in absorbance
(ABS) and total organic carbon (TOC). The change in biotoxicity was monitored with Escherichia coli
and Vibrio fischeri. The improvement in biodegradability during oxidation was demonstrated through
5-day biochemical oxygen demand/chemical oxygen demand ratio and aerobic biological treatment.
The combination of O
3
/H
2
O
2
/UV and O
3
/UV showed the best performance for the reductions in ABS
and TOC. However, mineralization and detoxification were not perfect under the experimental
conditions that were used in this study. Therefore, for the ultimate treatment of TC compounds, it is
suggested that AOP treatment is followed by biological treatment, utilizing enhanced
biodegradability. In this study, aerobic biological treatment by Pseudomonas putida was performed
for O
3
/UV-treated TC. It was confirmed that O
3
/UV treatment improved TOC reduction and facilitated
complete mineralization in biological treatment.
Huyen Trang Luu
Kisay Lee (corresponding author)
Department of Environmental Engineering and
Energy,
Myongji University,
Yongin,
Kyongki 449-728,
Korea
E-mail: kisay@mju.ac.kr
Key words | advanced oxidation, biodegradability, biological treatment, biotoxicity, tetracycline
INTRODUCTION
The presence of antibiotic compounds in livestock runoff
and in discharges of pharmaceutical manufacturers or
hospitals can cause the occurrence of antibiotic-resistant
microorganisms which threaten normal functions of the eco-
system and public health. Therefore, the proper treatment of
antibiotic compounds in wastewater treatment systems has
become the subject of growing concern and scientific
interest.
However, many antibiotics are not metabolized com-
pletely in animals and humans, but also are not
completely removed in conventional wastewater treatment
processes. These compounds are hardly biodegradable in
usual biological processes due to their antibacterial nature
(Yang et al. ; Kim et al. ). Advanced oxidation pro-
cesses (AOPs) characterized by the generation of radical
species including hydroxyl radicals have proved to be effec-
tive in the removal of many antibiotic compounds. Among
the available AOP techniques, ozone-based advanced oxi-
dation is considered as a prospective candidate because
ozone itself is a good oxidation agent and also the source
of hydroxyl radicals when it is coupled with ultraviolet
irradiation or hydrogen peroxide (Legrini et al. ; Tam-
bosi et al. ).
Even though advanced oxidation processes including
ozone or ultraviolet (UV) are a known alternative option
for the degradation of antibiotics like tetracyclines (TCs)
(Oller et al. ; Yuan et al. ), treating antibiotic-
containing wastewater by AOP alone is costly compared to
treatment by biological processes. One way of reducing the
treatment cost is first treating the antibiotic-containing
wastewater with an AOP to degrade partially and to increase
biodegradability, and then return to a traditional biological
process to achieve further treatment (Yahiat et al. ), or
vice versa.
The family of TCs, including TC, chlortetracycline (CTC)
and oxytetracycline (OTC), is a widely used class of anti-
biotic compounds used as human and veterinary
medicines. The degradation of TCs by AOP has been studied
intensively. Wu et al.() investigated the ozonation of
TC, where the enhancement of biodegradability and the
reduction in bioluminescent toxicity and chemical oxygen
demand (COD) were achieved. Wang et al.(, )
1229 © IWA Publishing 2014 Water Science & Technology | 70.7 | 2014
doi: 10.2166/wst.2014.350
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