Advanced
Effects of Adding UV and H<sub>2</sub>O<sub>2</sub> on the Degradation of Pharmaceuticals and Personal Care Products during O<sub>3</sub>Treatment
Effects of Adding UV and H2O2 on the Degradation of Pharmaceuticals and Personal Care Products during O3Treatment
Environmental Engineering Research. 2011. Sep, 16(3): 131-136
Copyright ©2011, Korean Society of Environmental Engineering
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0/)which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • Received : June 06, 2010
  • Accepted : July 07, 2011
  • Published : September 30, 2011
Download
PDF
e-PUB
PubReader
PPT
Export by style
Share
Article
Author
Metrics
Cited by
TagCloud
About the Authors
Ilho Kim
Water Resources & Environment Research Department, Korea Institute of Construction Technology; Department of Construction Environment Engineering, University of Science & Technology, Korea Institute of Construction Technology, Goyang 411-712, Korea
Seogku Kim
Water Resources & Environment Research Department, Korea Institute of Construction Technology; Department of Construction Environment Engineering, University of Science & Technology, Korea Institute of Construction Technology, Goyang 411-712, Korea
Hyundong Lee
Water Resources & Environment Research Department, Korea Institute of Construction Technology; Department of Construction Environment Engineering, University of Science & Technology, Korea Institute of Construction Technology, Goyang 411-712, Korea
Hiroaki Tanaka
Research Center for Environmental Quality Management, Kyoto University, Shiga 520-0811, Japan
Abstract
The degradation of 30 pharmaceuticals and personal care products (PPCPs) subjected to O 3 , O 3 /UV, and O 3 /H 2 O 2 treatments were investigated using semi-batch tests and evaluated by their pseudo-first-order rate constants. The additional application of UV or H 2 O 2 during O 3 treatment significantly improved the degradation rate of most of the PPCPs. At the same O 3 feed rate, O 3 /UV treatment exhibited much higher PPCP degradation efficiency than that of O 3 treatment. This was probably due to degradation of the PPCPs by O 3 , direct UV photodegradation, and OH radicals that formed from the photodegradation of O 3 during O 3 /UV treatment. PPCP degradation by O 3 was also promoted by adding H 2 O 2 during the O 3 treatment. However, when the initial H 2 O 2 concentration was high during O 3 treatment, OH radicals were likely to be scavenged by excess H 2 O 2 , leading to low PPCP degradation. Therefore, it is important to determine the appropriate H 2 O 2 dosage during O 3 treatment to improve PPCP degradation when adding H 2 O 2 during O 3 treatment.
Keywords
1. Introduction
The main reasons for the use of O 3 are disinfection and oxidation such as taste and odor control, decolorization, and elimination of micropollutants. Similar to other disinfectants such as chlorine or chlorine dioxide for water treatment, O 3 is unstable in water, and undergoes reactions with some water matrix components.However, O 3 decomposes, generating OH radicals,which are strong oxidants in water [1] . The disinfection process occurs mainly through the reaction of O 3 molecules, whereas the oxidation process may occur through both O 3 and OH radicals [2] . O 3 reacts with a variety of inorganic and organic compounds.However, the fact that rate constants for the O 3 reaction range over several orders of magnitude means that O 3 is a very selective oxidant. O 3 reacts quickly with phenols, amines, compounds with C = C double bonds, and aromatic compounds.
O 3 -based advanced oxidation processes (AOPs) are applied to oxidize O 3 -resistant compounds such as pesticides and chlorinated solvents by OH radicals, which are powerful and non-selective oxidants. OH radicals react very quickly with various inorganic and organic compounds in water. Therefore, OH radicals also contribute to the oxidation of micropollutants.However, their efficiency is often limited by the scavenging effect of the water matrix. In O 3 -based AOPs, the formation of OH radicals is accelerated by increasing the pH of the water, by dosing H 2 O 2 , or by adding UV irradiation. This ensures faster oxidation of O 3 -resistant compounds.
Potential risks associated with the release of pharmaceuticals and personal care products (PPCPs) into the aquatic environment have become an increasingly important issue for environmental regulators and the pharmaceuticals industry [3] . Therefore,the use of appropriate PPCP removal technologies should be applied in wastewater treatment plants to limit the aquatic risk of PPCPs. Many studies have been conducted on the degradation of PPCPs by O 3 -based processes, showing that O 3 was the oxidant, although some PPCPs seem to resistant to O 3 [4 - 7] . A great variety of PPCPs are being used in daily life and have been detected in the water environment [3 , 8 , 9] . Nevertheless, a limited number of PPCPs have been investigated because of the difficulty of the PPCPs analysis. The objective of this study was to investigate the effects of H 2 O 2 and UV on the degradation of 30 PPCPs during O 3 treatment.
2. Materials and Methods
- 2.1. Selected PPCPs and Preparation of Test Water
The 30 PPCPs selected in this study consisted of analgesics,antiarrhythmic agents, antibiotics, bronchodilators, an antiitching drug, anticonvulsants, antineoplastic agents, insect repellents,a carbadox (antiparasitic agent) intermediate, and an N-methyl d-aspartate receptor antagonist. Detailed information on the 30 PPCPs and their analytical method using high performance liquid chromatography-mass spectroscopy/mass spectroscopy(HPLC-MS/MS) was provided in our previous study [10] . To examine the degradability of the 30 PPCPs using O 3 , O 3 /UV, and O 3 /H 2 O 2 , test water samples were prepared by spiking the 30 PPCPs into pure water obtained from Nisso Shoji Co., Ltd(Tokyo, Japan). The initial concentrations of the 30 PPCPs in the
PPT Slide
Lager Image
Semi-batch reactor for the O3 O3/UV and O3/H2O2 treatment experiments.
Measurement conditions of the high performance liquidchromatography-mass spectroscopy/mass spectroscopy (HPLCMS/MS) for the pharmaceuticals and personal care products(PPCPs) analysis
PPT Slide
Lager Image
Measurement conditions of the high performance liquidchromatography-mass spectroscopy/mass spectroscopy (HPLCMS/MS) for the pharmaceuticals and personal care products(PPCPs) analysis
test water samples ranged from 4.7 μg/L (mefenamic acid) to 147.6 μg/L (sulfamonomethoxine). The procedure for the preparation of the test water is described elsewhere [10] .
- 2.2. Analytical Method
The 30 PPCPs were quantified simultaneously with a HPLC/MS/MS. An HPLC Alliance Waters2695 separation module (Water Inc., Milford, MA, USA) and a Quattro micro API tandem mass spectrometer were used for the HPLC and the MS/MS, respectively.MassLynxTM Software (Waters) managed the control of the HPLC/MS/MS system and treatment of the data acquired during the operation of HPLC/MS/MS. A gradient elution analysis method by varying mobile phase polarity with time was adopted to simultaneously quantify the 30 PPCPs. Samples taken during the experiments were introduced directly to HPLC/MS/MS. Table 1 shows the measurement conditions for HPLC/MS/MS in detail.
- 2.3. Experimental Setup and Conditions
All of the experiments were conducted using a cylindrical stainless reactor ( Fig.1 ). The temperature of the test water samples was maintained at 20°C with a hot water circulator. The pH of all test water samples, prepared by spiking the 30 PPCPs into pure water (PW), was adjusted to 7.0 with a 1 M phosphate buffer solution. Treatment experiments started by continuously injecting O 3 gas into the reactor. We conducted three different treatment experiments (O 3 , O 3 /UV, and O 3 /H 2 O 2 ) to compare the degradation characteristics of each PPCP.
An O 3 treatment experiment was performed under three different O 3 feed rates of 0.15, 0.3, and 0.6 mg/L/min. In this study,O 3 feed rate was controlled by supplying O 3 gas to the reactor at concentrations of 3.3, 6.6, and 13.2 mg/L, respectively, and by maintaining the flow rate of O 3 gas at a constant 1.0 L/min during all experiments.
An 8 W low-pressure mercury lamp emitting radiation at 254 nm with a UV intensity of 0.384 mW/cm2 was used for O 3 /UV treatment. The O 3 /UV treatment was performed on test water prepared with PW at O 3 feed rates of 0.15, 0.3, and 0.6 mg/L/min.The O 3 /H 2 O 2 treatment was performed by adding H 2 O 2 solution to the test water before O 3 treatment. Initial H 2 O 2 concentrations of 2.3 mg/L and 11.2 mg/L in the test water prepared with PW were used, and the O 3 feed rate was 0.6 mg/L/min in both experiments.
3. Results and Discussion
- 3.1. Determination of the PPCP Rate Constants for the O3, O3/UV, and O3/H2O2Treatments
The degradation reaction of an organic compound by O 3 is generally expressed as [11] :
PPT Slide
Lager Image
where [C] is the concentration of the organic compound, k is the first order rate constant, [O 3 ] is the concentration of dissolved O 3 , and k'O 3 is the pseudo first-order rate constant. Pseudo firstorder conditions are met if [O 3 ] ≥ ~10 × [C], and [O 3 ] does not
PPT Slide
Lager Image
Decrease in concentration of NN-diethyl-m-toluamide(DEET) with time during O3 O3/UV and O3/H2O2 treatments (O3 feed rate: 0.6 mg/L/min UV intensity: 0.384 mW/cm2 initial H2O2 concentration: 11.2 mg/L).
self-decay significantly during the reaction [12] . For experiments using the same reactor, the k'O 3 value can be used as an indicator for the reactivity of an organic compound with O 3 . Integrating Eq. (1), we obtain
PPT Slide
Lager Image
where Ct is the concentration of the organic compound at the reaction time t, and C0 is the initial concentration of the organic compound.
In the case of O 3 /UV treatment, the organic compound is degraded by O 3 , direct UV photodegradation, and OH radicals formed by UV photodegradation of O 3 . Therefore, the decrease in concentration of the organic compound during O 3 /UV treatment can be expressed as:
PPT Slide
Lager Image
Integrating Eq. (3), we obtain
PPT Slide
Lager Image
where L is the reactor optical light path (cm), I0 is the UV intensity(einstein/sec), ø is the quantum yield (mol/photon), ε is the molar extinction coefficient of the organic compound (/M/cm),kR is the second-order rate constant of OH radicals, and [OH∙] is the concentration of OH radicals.
In the case of O 3 /H 2 O 2 treatment, the organic compound is mainly degraded by O 3 and OH radicals, so the decrease in concentration of the organic compound can be expressed as follows:
PPT Slide
Lager Image
Integrating Eq. (5), the following expression is obtained:
PPT Slide
Lager Image
If the ln(Ct/C0) of an organic compound decreases linearly with time, the degradation reaction of the compound by each treatment can be regarded as a pseudo-first-order reaction. In this case, the pseudo-first-order rate constants (k'O 3 , k'O 3 /UV, and k'O 3 /H 2 O 2 ) for O 3 , O 3 /UV, and O 3 /H 2 O 2 , respectively, are obtained from the slopes of each straight line.
Fig. 2 shows the decrease in concentration of N,N-diethylm-toluamide (DEET) for a reaction time of 5 min during the O 3 ,O 3 /UV, and O 3 /H2O2 treatments, which were conducted using test water samples prepared by simultaneously spiking the 30 PPCPs into pure water. O 3 was supplied to the reactor at a feed rate of 0.6 mg/L/min in all experiments. O 3 /H2O2 treatment was performed by supplying O 3 to the test water samples with an initial H2O2 concentration of 11.2 mg/L. Regardless of the treatment method, the DEET concentration decreased linearly with time. Therefore, the degradation reactions of DEET with O 3 , O 3 /UV, and O 3 /H2O2 conformed with pseudo-first-order reactions under the experimental conditions of this study. As shown in Fig. 2 ,the value of k'O 3 (the pseudo-first-order rate constant for O 3 )of DEET was 1.7 × 10-3/sec, whereas that of k'O 3 /H2O2 was slightly enhanced at 2.3 × 10-3/sec due to the contribution of OH radicals to DEET degradation. Moreover, the value of k'O 3 /UV increased by 2.6 × 10-3/sec as a result of adding UV to the O 3 treatment.
A linear decrease in concentration for a 5 min reaction time was shown by all of the PPCPs selected in this study, irrespective of the applied treatment methods, and the pseudo-first-order rate constants of the 30 PPCPs for each process could be obtained from the slope of each straight line. The pseudo-first-order rate constants were used to compare the degradability of the 30 PPCPs using each treatment method as well as the effects of adding H 2 O 2 and UV during O 3 treatment on PPCP degradation.
- 3.2. Effect of UV on PPCP Degradation during O3Treatment
Fig. 3 compares the pseudo first-order rate constants of the 30 PPCPs for O 3 treatment with/without UV under O 3 feed rates of 0.15, 0.3, and 0.6 mg/L/min, respectively. The combination of UV during O 3 treatment led to a distinct improvement in degradation rates of most of the PPCPs. Rate constants of several PPCPs such as ketoprofen, diclofenac, sulfamethoxazole, and antipyrine increased considerably by adding UV during the O 3 treatment. In particular, ketoprofen and diclofenac showed much higher rate constants than those for O 3 treatment, regardless of the O 3 feed rate. Our previous study showed that ketoprofen and diclofenac are degraded very easily with UV, indicating that direct UV photodegradation mainly contributes to its degradation during UV/H 2 O 2 treatment [11] . In this study, it was thought that such fast degradation of ketoprofen and diclofenac could be attributed to direct UV photodegradation rather than to OH radicals during O 3 /UV treatment.
The degradation efficiencies of the 30 PPCPs with each treatment were compared to investigate the effect of O 3 feed rate on PPCP degradation during the O 3 and O 3 /UV treatments. The degradation efficiency was calculated as the ratio of the average rate constant (/sec) for all PPCPs to the O 3 consumption per volume of reactor (mg/L). As a result, 1.6 × 10-3, 2.2 × 10-3, and 1.8× 10-3 L/mg/sec were obtained for O 3 feed rates of 0.15, 0.3, and 0.6 mg/L/min, respectively, during O 3 treatment. The degradation efficiencies following O 3 /UV treatment were 6.9 × 10-3, 3.8 ×10-3, and 3.3 × 10-3 L/mg/sec for O 3 feed rates of 0.15, 0.3, and 0.6 mg/L/min, respectively, showing apparently increased values compared to those for O 3 treatment. However, in contrast to the O 3 treatment, the highest degradation efficiency was observed at a low O 3 feed rate of 0.15 mg/L/min, indicating that the O 3 dose required for PPCP degradation can be reduced by combining UV and O 3 treatment.
PPT Slide
Lager Image
Comparison of rate constants of the 30 pharmaceuticals and personal care products (PPCPs) during O3 treatment with/without UV. (a)O3 feed rate 0.15 mg/L/min (b) O3 feed rate 0.3 mg/L/min and (c) O3 feed rate 0.6 mg/L/min.
PPT Slide
Lager Image
Comparison of rate constants of the 30 pharmaceuticals and personal care products (PPCPs) during O3 treatment with/without adding H2O2.
- 3.3. Effect of Adding H2O2on PPCP Degradation during O3Treatment
Fig. 4 compares the rate constants of the 30 PPCPs after O 3 /H2O2 treatment with the k' values obtained for O 3 treatment using an O 3 feed rate of 0.6 mg/L/min. O 3 /H2O2 experiments were conducted by maintaining the initial H2O2 concentrations in tested water at 2.3 mg/L and 11.2 mg/L before injecting O 3 gas into the tested water. No variation was observed in the PPCP concentrations when only H2O2 was added to the PPCP-tested water. Here, the rate constants of 28 PPCPs were discussed, except ceftiofur and chlorotetracycline, for which peaks were not observed. O 3 treatment combined with an initial H2O2 concentration of 2.3 mg/L showed 1.1 to 6.5 times higher rate constants for 26 PPCPs than those for O 3 treatment alone. This was due to the contribution of OH radicals formed by the reaction of Eq. (7) [13] . However, the DEET and tetracycline rate constants did not improve despite combining the H2O2 and the O 3 treatment.
PPT Slide
Lager Image
The rate constants of 17 PPCPs (2-QCA, acetaminophen,antipyrine, carbamazepine, clarithromycin, clenbuterol, crotamiton,DEET, fenoprofen, ifenprodil, isopropylantipyrine, mefenamic acid, metoprolol, naproxen, oxytetracycline, propranolol,and sulfamonomethoxine) increased by 1.1 to 1.6 times when an initial H 2 O 2 concentration of 11.2 mg/L was combined with the O 3 treatment. In particular, even slightly lower rate constants than for the O 3 treatment alone were observed in four PPCPs such as cyclophosphamide, disopyramide, tetracycline, and theophylline.Moreover, the average rate constants of the 28 PPCPs for 2.3 mg/L and 11.2 mg/L were 6.2 × 10-3/sec and 5.1 × 10-3/sec,respectively, indicating that a higher H 2 O 2 concentration does not necessarily lead to a faster PPCP reaction. The one reason why a high H 2 O 2 concentration cannot ensure a fast reaction with the target compound is the consumption of OH radicals formed during O 3 treatment by excess H 2 O 2 . OH radicals can be scavenged by H 2 O 2 in water as shown in Eq. (8) [13] , leading to a low degradation rate of the target compounds.
PPT Slide
Lager Image
When a high initial H 2 O 2 concentration of 11.2 mg/L was added, OH radicals formed by the reaction of Eq. (7) were scavenged by excess H 2 O 2 added during the O 3 treatment; thus, lower rate constants than those for O 3 /H 2 O 2 treatment using low H 2 O 2 concentration of 2.3 mg/L were obtained. This result indicates that it will be important to determine the appropriate H 2 O 2 dose for O 3 treatment to improve reaction rates of PPCPs by adding H 2 O 2 during O 3 treatment.
4. Conclusions
This study investigated the effects of adding H 2 O 2 and UV on the degradation of 30 PPCPs during O 3 treatment. The new findings from this study are as follows:
  • 1) Degradation reactions of the target PPCPs with O3, O3/H2O2,and O3/UV could be expressed by pseudo-first-order kinetics.
  • 2) The combination of UV or H2O2with O3promoted the degradation reactions of all PPCPs under the tested conditions due to direct UV photodegradation or OH radicals.
  • 3) Several PPCPs such as ketoprofen and diclofenac showed much higher rate constants during O3/UV treatment than those during O3/H2O2treatment, indicating that their degradation can be attributed to direct UV photodegradation rather than OH radicals.
  • 4) From a comparison of degradation efficiency, defined as the ratio of the average rate constant (/sec) for all PPCPs to the O3consumption per reactor volume (mg/L), the highest degradation efficiency was obtained at an O3feed rate of 0.3 mg/L/min during O3treatment. In contrast, an O3feed rate of 0.15 mg/L/min produced optimum degradation efficiency during O3/UV treatment. This result indicates that the O3dose required for PPCP degradation by O3can be reduced by combining it with UV.
  • 5) PPCP degradation by O3was promoted by adding H2O2during the O3treatment. However, when a high initial H2O2concentration was added during the O3treatment, formed OH radicals were likely to be scavenged by excess H2O2, leading to low PPCP degradation. Therefore, it is important to determine the appropriate H2O2dosage during O3treatment to improve PPCP degradation by adding H2O2during O3treatment.
Acknowledgements
This study was funded by the Japan Science and Technology Agency with partial funding by the Korea Institute of Construction Technology.
References
Staehelin J , Hoigne J 1985 Decomposition of ozone in water in the presence of organic solutes acting as promoters and inhibitors of radical chain reactions Environ. Sci. Technol 19 1206 - 1213
Langlais B , Reckhow DA , Brink DR 1991 American Water Works Association Research Foundation Compagnie ge?ne?rale des eaux. Ozone in water treatment: application and engineering:cooperative research report Lewis Publishers Chelsea
Jørgensen SE , Halling-Sørensen B 2000 Drugs in the environment Chemosphere 40 691 - 699
Andreozzi R , Caprio V , Marotta R , Radovnikovic A 2003 Ozonation and H2O2/UV treatment of clofibric acid in water: a kinetic investigation J. Hazard. Mater 103 233 - 246
Huber MM , Canonica S , Park GY , von Gunten U 2003 Oxidation of pharmaceuticals during ozonation and advanced oxidation processes Environ. Sci. Technol 37 1016 - 1024
Oh BS , Jang HY , Hwang TM , Kang JW 2007 Role of ozone for reducing fouling due to pharmaceuticals in MF (microfiltration)process J. Membr. Sci 289 178 - 186
Dantas RF , Canterino M , Marotta R , Sans C , Esplugas S , Andreozzi R 2007 Bezafibrate removal by means of ozonation: primary intermediates kinetics and toxicity assessment Water Res. 41 2525 - 2532
Nakada N , Komori K , Suzuki Y , Konishi C , Houwa I , Tanaka H 2007 Occurrence of 70 pharmaceutical and personal care products in Tone River basin in Japan Water Sci. Technol 56 133 - 140
Okuda T , et al. , Kobayashi Y , et al. , Nagao R , et al. 2008 Removal efficiency of 66 pharmaceuticals during wastewater treatment process in Japan Water Sci. Technol et al. 57 65 - 71
Kim I , Tanaka H 2009 Photodegradation characteristics of PPCPs in water with UV treatment Environ Int. 35 793 - 802
Hoigne J , Bader H 1983 Rate constants of reactions of ozone with organic and inorganic compounds in water. I. Non-dissociating organic compounds Water Res. 17 173 - 183
Buffle MO 2006 Mechanistic investigation of the initial phase of ozone decomposition in drinking water and wastewater:impact on the oxidation of emerging contaminants disinfection and by-products formation [dissertation] Technische Hochschule Zuerich Zuerich:Eidgenoessische
von Gunten U 2003 Ozonation of drinking water. Part I. Oxidation kinetics and product formation Water Res 37 1443 - 1467