Infrastructure. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine. Co-published by

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1 Infrastructure Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine Co-published by

2 INFR6SG09 DEMONSTRATING ADVANCED OXIDATION COUPLED WITH BIODEGRADATION FOR REMOVAL OF CARBAMAZEPINE by: Karl Linden Olya Keen University of Colorado Boulder Nancy G. Love University of Michigan Diana S. Aga University of Buffalo 2012

3 The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality research for its subscribers through a diverse public-private partnership between municipal utilities, corporations, academia, industry, and the federal government. WERF subscribers include municipal and regional water and wastewater utilities, industrial corporations, environmental engineering firms, and others that share a commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life. For more information, contact: Water Environment Research Foundation 635 Slaters Lane, Suite G-110 Alexandria, VA Tel: (571) Fax: (703) werf@werf.org This report was co-published by the following organization. IWA Publishing Alliance House, 12 Caxton Street London SW1H 0QS, United Kingdom Tel: +44 (0) Fax: +44 (0) publications@iwap.co.uk Copyright 2012 by the Water Environment Research Foundation. All rights reserved. Permission to copy must be obtained from the Water Environment Research Foundation. Printed in the United States of America IWAP ISBN: / X This report was prepared by the organization(s) named below as an account of work sponsored by the Water Environment Research Foundation (WERF). Neither WERF, members of WERF, the organization(s) named below, nor any person acting on their behalf: (a) makes any warranty, express or implied, with respect to the use of any information, apparatus, method, or process disclosed in this report or that such use may not infringe on privately owned rights; or (b) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in this report. University of Buffalo, University of Colorado Boulder, University of Michigan The research on which this report is based was developed, in part, by the United States Environmental Protection Agency (EPA) through Cooperative Agreement No. CR with the Water Environment Research Foundation (WERF). However, the views expressed in this document are not necessarily those of the EPA and EPA does not endorse any products or commercial services mentioned in this publication. This report is a publication of WERF, not EPA. Funds awarded under the Cooperative Agreement cited above were not used for editorial services, reproduction, printing, or distribution. This document was reviewed by a panel of independent experts selected by WERF. Mention of trade names or commercial products or services does not constitute endorsement or recommendations for use. Similarly, omission of products or trade names indicates nothing concerning WERF's or EPA's positions regarding product effectiveness or applicability. ii

4 The authors thank Alexi Ernstoff and Sherri Cook (University of Michigan) for their assistance during various phases of this project. They also thank the participating utilities, especially staff at both the 75 th Street Wastewater Facility in Boulder, Colorado and the PARCC Side Clean Water Plant in Grand Rapids, Michigan. Research Team Principal Investigators: Diana S. Aga, Ph.D. University of Buffalo Karl Linden, Ph.D. University of Colorado Boulder Nancy G. Love, Ph.D., P.E., BCEE University of Michigan Project Team: Olya Keen, Ph.D. student University of Colorado Boulder Seungyun Baik, Ph.D. student University of Buffalo WERF Project Subcommittee Zia Bukari American Water Paul J. Delphos, P.E. Black & Veatch Kendall Jacob, P.E. Cobb County Water System, Cobb County Government Samuel S. Jeyanayagam, Ph.D., P.E., BCEE CH2M Hill Patrick Jjemba, Ph.D. American Water Innovative Infrastructure Research Committee Stephen P. Allbee U.S. Environmental Protection Agency Frank Blaha Water Research Foundation Peter Gaewski, MS, P.E. Tata & Howard, Inc. ACKNOWLEDGMENTS Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine iii

5 Kevin Hadden Orange County Sanitation District David Hughes, P.E. American Water Kendall Jacob, P.E. Cobb County Water System, Cobb County Government Jeff Leighton City of Portland Water Bureau Daniel Murray U.S. Environmental Protection Agency Michael Royer U.S. Environmental Protection Agency Steve Whipp United Utilities North West Walter L. Graf, Jr. Water Environment Research Foundation Daniel M. Woltering, Ph.D. Water Environment Research Foundation Water Environment Research Foundation Staff Director of Research: Program Director: WERF Treatment Technology Liaison Daniel M. Woltering, Ph.D. Walter L. Graf, Jr. Amit Pramanik, Ph.D., BCEEM iv

6 Abstract: ABSTRACT AND BENEFITS Carbamazepine is an anthropogenic pharmaceutical found in wastewater effluents that is quite resistant to removal by conventional wastewater treatment processes. Hydroxyl radicalbased advanced oxidation process can transform carbamazepine into degradation products but cannot mineralize it in an economically efficient manner. This study evaluated the combination of ultraviolet plus hydrogen peroxide (UV-H 2 O 2 )-based advanced oxidation and biodegradation to enable carbamazepine removal; specifically, to determine whether the products of the advanced oxidation of carbamazepine can be further biodegraded by activated sludge microbial communities. The fate of 14 C carbamazepine was followed through benchscale advanced oxidation followed by biodegradation using liquid scintillation counting, and by liquid chromatography with either a mass spectrometric or a radiochemical detection. The results illustrate that carbamazepine oxidation products can be mineralized by activated sludge bacteria. This outcome suggests that combining advanced oxidation with a biologically active filtration treatment step can be effective for carbamazepine removal. This same treatment strategy should be evaluated for its effectiveness with other biologically recalcitrant organic micropollutants. Advanced oxidation followed by biodegradation may be a viable option for applying tertiary wastewater treatment to achieve trace contaminant removal. Benefits: Demonstrates that advanced oxidation coupled with biodegradation mineralizes carbamazepine in wastewater. Indicates that persistent pharmaceuticals in wastewater effluent can be treated with a combination of chemical and biological oxidation. Introduces a biodegradation protocol for assessing the biodegradability of synthetic organic compounds. Keywords: Micropollutants, pharmaceuticals, biodegradation, mineralization, carbamazepine, advanced oxidation, oxidation products. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine v

7 TABLE OF CONTENTS Acknowledgments... iii Abstract and Benefits...v List of Tables... vii List of Figures... vii Executive Summary...ES Project Approach Introduction Chemicals, Samples, and Cultures Analytical Methods Experimental Protocols Preliminary Studies Sample Preparation Advanced Oxidation Biodegradation Results Fundamental Properties of Carbamazepine Relevant to Advanced Oxidation Advanced Oxidation of Nitrified Effluents Biodegradation of CBZ in Effluents With and Without AOP AOP Byproduct Formation and Biological Fate Conclusions References...R-1 vi

8 LIST OF TABLES 2-1 Boulder Wastewater Treatment Plant Effluent Quality During Two Sampling Events LIST OF FIGURES 1-1 Carbamazepine Structure and Location of 14 C Atom Experimental Setup for Assessing the Biological Stability of Effluents Treated with AOP Versus Those Not Treated with AOP Degradation of 10 mg/l of H 2 O 2 with 0.4 mg/l of Bovine Catalase Oxidation Products Retained After Rotary Evaporation Compared to Solid Phase Extraction AOP Degradation of CBZ in Nitrified Effluent Under Medium Pressure UV Without H 2 O 2 and With 5 mg/l H 2 O Fraction of CBZ Remaining in Nitrified Effluent Under Medium Pressure UV Without H 2 O 2 and With Various Doses of H 2 O Change in SUVA 254 and Nitrate Concentration During Storage of Effluent with Activated Sludge, Both With and Without CBZ Radioactivity of Effluents Before and After AOP (1800 mj/cm 2 UV Fluence and 10 mg/l H 2 O 2 Dose) in the Absence of Activated Sludge Inoculum Biodegradation Experimental Results Show that CBZ Was Mineralized Only in AOP-Treated Effluents Radiochromatogram of AOP Treated and Untreated Samples Before Biodegradation and After Biodegradation MS Chromatogram of the AOP-Treated Effluent Before Biodegradation and After Biodegradation Proposed Products of CBZ Advanced Oxidation Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine vii

9 LIST OF ACRONYMS AOP Advanced Oxidation Process CBZ EE2 ESI Carbamazepine 17α-Ethinyl Estradiol Electrospray ionization HPLC High performance liquid chromatography ITMS Ion trap mass spectrometry LC/MS LP Liquid chromatography/mass spectrometry Low Pressure LSC Liquid scintillation counter MP pcba Medium pressure para-chlorobenzoic acid QY Quantum yield SPE Solid phase extraction SUVA 254 Specific UV absorbance at 254 nm TOC Total organic carbon TOrCs TSS Trace organic chemicals Total Suspended Solids UV Ultraviolet treatment WWTP Wastewater treatment plant viii

10 EXECUTIVE SUMMARY Carbamazepine (CBZ) is an anti-seizure drug that has been detected in wastewaterimpacted environments worldwide. CBZ is very difficult to remove or degrade by all conventional and most advanced wastewater treatment technologies. Advanced oxidation processes (AOPs) are used for treating chemical contaminants in drinking water and reuse water applications, but have not yet been widely accepted for wastewater treatment. The objectives of the study were to 1) determine whether AOP can degrade CBZ in wastewater matrices and 2) to evaluate whether the products of advanced oxidation of CBZ are more biodegradable than the parent compound. First, the researchers examined whether ultraviolet (UV) light combined with hydrogen peroxide (H 2 O 2 ) AOP can oxidize CBZ to primary products using conditions bounded by those currently accepted by the drinking water and reuse water industry for this technology (up to 2000 mj/cm 2 UV fluence and up to 20 mg/l H 2 O 2 dose). The fundamental properties of CBZ degradation during AOP were analyzed and it was found that CBZ was transformed almost entirely (>90%) within a dose of 2000 mj/cm 2 and up to 10 mg/l H 2 O 2 in wastewater matrices. Interestingly, studies showed that when an effluent high in nitrate (> 9 mg/l as N) is irradiated with medium pressure (MP) UV, it creates hydroxyl radicals from nitrate while production of radicals from H 2 O 2 decreases due to a shielding effect caused by nitrate s absorbance. Therefore, at low H 2 O 2 concentrations, most of the radicals were formed by nitrate and the addition of H 2 O 2 was redundant. The identity of the oxidation degradation products were proposed based on mass fragmentation pattern obtained by mass spectrometry, but no mineralization occurred. The degradation was attributed mainly to the reaction between the parent compound and the hydroxyl radicals produced during AOP treatment, and partially to direct UV photolysis (<10% of overall degradation). Following AOP evaluation, the potential for biodegradation of the oxidation and photolysis products by activated sludge microbial community was examined. An experimental system was set up to test the differences in the extent of biodegradation of the pre-aop and post- AOP treated CBZ after 8-10 days and days. Radiolabeled 14 C-CBZ was used as the parent compound, which allowed the degree of mineralization to be quantified by analyzing the amount of 14 CO 2 generated during the biodegradation process. Biodegradation experiments showed that a significant fraction of the AOP products was mineralized. The results of this study show the benefit of using AOP-coupled biodegradation to mineralize CBZ, which is an otherwise biologically recalcitrant trace contaminant. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine ES-1

11 ES-2

12 CHAPTER 1.0 PROJECT APPROACH 1.1 Introduction Pharmaceuticals in wastewater effluent have been a concern for water and wastewater treatment and reuse industries for many years. Among them is carbamazepine (CBZ), an antiseizure drug that has been detected in wastewater effluents and impacted streams worldwide (Kolpin et al., 2002; Loos et al., 2010; Zhou et al., 2010). It is known to be persistent to both traditional and most advanced wastewater treatment process (Clara et al., 2005; Xue et al., 2010). It does, however, get transformed to product compounds by advanced oxidation processes (AOP) (Pereira et al., 2007; Lee and von Gunten, 2010). Unknown transformation products are a concern for oxidative processes and, indeed, acridine, a mutagen, is a known transformation product of CBZ when treated with AOP (Vogna, 2004). To date, very few studies have examined whether oxidation products of trace organic compounds (TOrCs) are biodegradable (Watts and Linden, 2008). Many TOrCs are biotransformed to some degree by biological processes during wastewater treatment, but studies on the biologically-derived byproducts (metabolites) are rare, mainly because doing so is best done using radiolabeled forms. Recent studies by this team on the biotransformation potential of 17α-ethinylestradiol (EE2) and trimethoprim show that stable, more polar biotransformation intermediates are formed during biological degradation and may remain in effluents, even when the parent compound is largely biotransformed or sorbed (Skotnicka-Pitak et al., 2009; Khunjar et al., 2011). Evaluation of the biological activity or toxicity of these byproducts is largely unstudied and therefore unknown. Microfiltration and ultrafiltration membrane processes are largely ineffective at enhancing further removal of the most recalcitrant, polar TOrCs and certainly of polar biotransformation products. Untransformed TOrCs (e.g., carbamazepine) and biotransformed intermediates will ultimately be treated further by oxidation processes employed for disinfection. A growing number of wastewater treatment plants (WWTPs) are deploying UV disinfection, especially in treatment plants employing membrane bioreactors. Coupling ultraviolet (UV) disinfection with oxidation processes (such as hydrogen peroxide (H 2 O 2 ) addition coincident with UV) can enable simultaneous disinfection of pathogens and oxidation of TOrCs in a single process. Numerous studies suggest that germicidal UV lamps, coupled with hydrogen peroxide, are effective at transforming recalcitrant organic compounds (Rosenfeldt and Linden, 2004; Pereira et al., 2007). However, few experiments with UV-advanced oxidation have been done on wastewater effluents (Rosario-Ortiz et al., 2010), and the biodegradability of the oxidized products derived from pharmaceuticals in effluents have not previously been determined. The goal of the study was to evaluate whether UV/H 2 O 2 advanced oxidation followed by downstream biological treatment can mineralize CBZ. It has been repeatedly shown that CBZ is Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 1-1

13 recalcitrant through biological treatment processes, therefore treatment processes that can remove CBZ from wastewater may be valuable in removing many other TOrCs. Effluents were collected upstream of chlorine-based disinfection from the Boulder wastewater treatment plant, which achieves biological nutrient removal with gravity clarification and low effluent TSS. All experiments were performed in the laboratory. The objectives for this project were: Objective 1: Determine the rate and extent of carbamazepine transformation and byproduct formation by UV-based advanced oxidation. Objective 2: Determine the rate and extent to which pharmaceutical byproducts generated by the UV-based advanced oxidation process biodegrade. Individually, neither UV/H 2 O 2 advanced oxidation nor biological treatment is effective at mineralizing CBZ. However, when the two processes are combined they represent a more comprehensive approach for addressing pharmaceuticals in wastewater that may lead to full mineralization of otherwise recalcitrant compounds. The potential for UV/H 2 O 2 advanced oxidation to oxidize the CBZ to its primary products within UV conditions utilized in the drinking water and reuse water industry (up to 2000 mj/cm 2 UV fluence and up to 20 mg/l H 2 O 2 dose) was evaluated. Subsequently, it was determined whether the oxidation and photolysis products were amenable to biodegradation by activated sludge communities. 1.2 Chemicals, Samples, and Cultures All chemicals used in the study were reagent grade. Sodium azide (Alfa Aesar, Ward Hill MA) 1 M stock solution was prepared for deactivating biological activity in abiotic controls. Hydrogen peroxide (J.T. Baker, Phillipsburg NJ) was used during advanced oxidation treatments to produce hydroxyl radicals. A stock solution of 1,000 mg/l (2950 units/mg) of bovine catalase was prepared (Sigma-Aldrich, St. Louis, MO) for hydrogen peroxide quenching before the activated sludge inoculum was added to AOP-treated samples. Non-radiolabeled (cold) CBZ was manufactured by Acros Organics (Geel, Belgium) and radiolabeled (hot) CBZ was purchased from Sigma Radiochemicals (St. Louis, MO). A stock solution of cold CBZ was prepared in methanol. Hot CBZ was labeled with C-14 carbon in the location identified in Figure 1-1. The specific activity of the stock solution was 22.6 mci/mol. The solution contained 1.11 mm of hot CBZ in methanol. Figure 1-1. Carbamazepine Structure and Location of 14 C Atom (marked with *). Activated sludge bacteria and pre-disinfected secondary effluent were obtained from the Boulder Wastewater Treatment Plant (BWWTP). The effluent was filtered through a 0.2 micron nylon filter (Millipore, Billerica MA) to remove particulate matter and microorganisms that could interfere with the experimental procedures. This ensured that all biological assays, which received a microbial spike at the start, were initiated with the same microbial concentration. The activated sludge biomass concentration was measured as volatile suspended solids (VSS) using Standard Method 2540E (20 th ed.) and Pall type A/E glass fiber filters (Pall, Port Washington NY). 1-2

14 1.3 Analytical Methods The Quality Assurance Project Plan (QAPP) developed at the start of the study, which outlined the quality assurance and quality control measures to be taken for the analytical methods, were followed during this research effort. Reaction rates of CBZ with hydroxyl radical ( OH) were determined using competition kinetics with para-chlorobenzoic acid (pcba) as a probe compound. Reaction rate constant of pcba with hydroxyl radical ( OH) is well established: k OH,pCBA = M -1 s -1 (Buxton et al. 1988). The decay process of the compound during AOP is second order and is a function of the target compound concentration and the concentration of the OH. The concentration of OH stays relatively constant throughout the treatment and as a result, the contaminant decay can be modeled as a first order process with the observed pseudo-first order reaction rate constant k 1 = k OH,M [ OH]. The decay of the compound with time is then described by the following expression: k1t C( t) C0e where C(t) is the concentration of the contaminant at time t and C 0 is the initial concentration. When ln[c(t)/c 0 ] is plotted vs. time, the slope of the line is the first order reaction rate constant. The ratio of the slopes of the two compounds is the ratio of their reaction rate constants, so with one reaction rate constant known the other one is calculated. The contribution of the direct photolysis to the overall observed decay of the target compound has to be factored out before the analysis: k 1 = k T - k hv where k 1 is the first-order reaction rate constant of the contaminant with hydroxyl radical, k T is the total observed reaction rate constant, and k hv is the rate constant of the photolytic decay of the contaminant. Quantum yield of photolysis (QY) in both low pressure (LP) and medium pressure (MP) UV systems was calculated using the method by Sharpless and Linden (Sharpless and Linden, 2003): k' k s d ( ) where E k ( ) s 0 ( ) ( )[1 10 U ( ) a( ) z a( ) z The varibales of the equation are defined as follows: Φ = quantum yield k d = time based rate constant of parent transformation, s -1 k s = specific photon absorption rate, Es mol -1 s -1 E 0 = insident wavelength irradiance J s -1 cm -2 ε = molar absorption coefficient of the target compound, M -1 cm -1 U = energy of the given wavelength, J Es -1 a = solution absorbance, cm -1 z = sample depth, cm The conversion between the time based (k d ) and fluence based (k d ) reaction rate 2 1 J cm constants is k' d Eavg kd where E 2 avg is the average irradiance calculated s s cm J using the method by Bolton and Linden (Bolton and Linden, 2003). Hydrogen peroxide was measured using the triiodide method (Klassen et al., 1994). Radiolabeled CBZ was measured using a liquid scintillation counter (Packard, 1600 TR). Ultima ] Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 1-3

15 Gold scintillation cocktail (Perkin Elmer, Waltham MA) was selected due to its efficiency for highly alkaline solutions as reported by the manufacturer. Optimal sample to cocktail ratios were selected by testing several ratios: 2 ml of sample to 5 ml of cocktail, 1 ml to 6 ml and 0.2 ml to 6.8 ml. All ratios performed equally well, so the smallest sample concentration was selected: 0.2 ml of sample to 6.8 ml of cocktail. Because low concentration of radiolabeled CO 2 was expected in the alkaline trap, 1 ml sample to 6 ml cocktail ratio was selected for the traps. This ratio provided the highest volume of the alkaline solution that did not result in cloudiness in the scintillation vials. Analysis for CBZ and byproducts in samples occurred using a liquid chromatograph with ion trap mass spectrometer (LC-ITMS) detection [LCQ Advantage, Thermo Finnigan, CA, USA] equipped with a UV 6000LP UV-Vis diode array detector. Analysis was performed using an electrospray ionization (ESI) source in positive ion mode under full-scan conditions, from 50 to 500 m/z. Nitrogen gas was used for sheath gas with the flow of 24 arbitrary unit. Electrospray voltage was 4500 V and capillary temperature and voltage were 250ºC and 41 V, respectively. Separation was achieved using a Thermo Scientific Betabasic-18 C 18 column, (100 X 2.1 mm i.d, 3 µm particle size, Thermo Fisher Scientific, Waltham, MA), equipped with a guard cartridge (10 X 2.1 mm i.d., 3 µm particle size, Thermo Fisher Scientific, Waltham, MA). The gradient mobile phase consisted of LC/MS-grade acetonitrile (A, Honeywell B & J, Muskegon, MI) and nanopure water with 0.3% formic acid (B). The initial conditions were 2% A and 98% B; after 5 minutes A was increased to 95% over 15 minutes, and then held at the same condition for 4 more minutes. The initial mobile phase condition was then restored within one minute and run for 5 more minutes to maintain the condition. The flow rate was set at 200 µl/min, the injection volume was 10 µl, and the column oven temperature was held at 30ºC. The total run time was 30 minutes including post-run protocols. Radioactive samples were analyzed using a Surveyor HPLC (Thermo Finnigan, San Jose, CA) equipped with an on-line radiochromatographic detector (IN/US Systems, Inc., Tampa, FL) which uses a flow through cell with a volume of 0.5 ml and a 3:1 scintillation fluid: eluent ratio (Ecoscint, National Diagnostics, Atlanta, GA). For some samples, solid phase extraction (SPE) was performed in order to clean up and concentrate the samples. Phenomenex Strata -X (Polymeric Reversed Phase, 200 mg, 3 ml) cartridges were pre-conditioned with 3 ml HPLC-grade methanol (Honeywell B & J, Muskegon, MI) and washed with 3 ml nanopure water. Cartridges were then loaded with 1 ml sample and 2 ml nanopure water mixture. Eluates were collected for further analysis by radioactive counting using a liquid scintillation counter (LSC, Packard Tri-Carb, Downers Glove, IL). Cartridges were then washed with 4 ml 5% (v/v) HPLC-grade methanol and the eluates were collected for further analysis by LSC. After 1 minute of drying, cartridges were eluted with 4 ml 50:50 of HPLC-grade methanol and acetonitrile (Sigma-Aldrich, St. Louis, MO). Eluates were then evaporated under a slow flow of nitrogen to almost dryness and diluted with nanopure water to a final sample volume of 0.2 ml for HPLC/radiochromatography analysis, as described above. 1-4

16 1.4 Experimental Protocols The Quality Assurance Project Plan (QAPP) developed at the start of the study, which outlined the quality assurance and quality control measures to be taken in carrying out the experimental protocols, were followed during this research effort Preliminary Studies A preliminary study was conducted to determine if activated sludge inoculum requires acclimatization to the CBZ concentrations that would be used in the study. BWWTP effluent samples were diluted with tap water that was dechlorinated by irradiation with medium pressure (MP) UV. Loss of free chlorine in the tap water was confirmed using the Hach colorimentric DPD method (Hach, Inc., Loveland CO). The dilution of effluent with tap water was used to limit the availability of organic matter for the bacteria in the study, so a measurable change in several parameters can be detected in the solution over seven days. The parameters monitored were nitrate, total organic carbon (TOC) and UV absorbance at 254 nm (UV 254 ). TOC and UV 254 were used to calculate specific UV absorbance (SUVA 254 ) using the following formula: UV SUVA254, where [TOC] is the organic carbon concentration in mg/l. TOC was [ TOC] measured with a Shimadzu TOC-V CSH organic carbon analyzer (Shimadzu America, Inc. Columbia MD), nitrate was measured with a Hach colorimetric method TNT835 (Hach, Inc., Loveland CO), and UV absorbance was measured with a Varian Cary-Bio100 spectrometer (Agilent Technologies, Santa Clara CA). UV 254 is higher per mg of organic carbon in organic matter that is terrestrial in nature and as a result more aromatic in character. As organic matter becomes more microbial in nature its aromaticity decreases and SUVA 254 decreases as well. Therefore, a steady decrease in SUVA 254 of the sample would indicate biological activity. A decrease in nitrate would also indicate biological denitrification by the activated sludge culture. It was experimentally determined that the best dilution ratio for these experiments was 10% effluent: 90% dechlorinated tap water. Two aerated bottles contained identical diluted effluent volumes and only one of them was spiked with 1 mg/l CBZ. Activated sludge was added to both bottles Sample Preparation Effluents were prepared for the biological degradation evaluation by spiking them with 10 mg/l of H 2 O 2, mg/l of radiolabeled CBZ (total activity of each 100 ml sample was 2.5 microci) and 1 mg/l of non-radiolabeled CBZ to boost the detection of products by LC/MS. The H 2 O 2 dose for the Boulder WWTP nitrified effluent was optimized separately and is discussed in Section 3-2. CBZ stock solutions were prepared by dissolving in methanol. Therefore, CBZ was spiked into effluents by removing the necessary volume of CBZ stock, allowing the methanol to evaporate, and then reconstituting dry CBZ with the effluent. Half of the CBZ-spiked solution did not receive subsequent AOP treatment while the other half was irradiated with 1800 mj/cm 2 of MP-UV. The UV dose was pre-determined using nonradiolabeled CBZ as the dose required for 90% degradation of the parent compound Advanced Oxidation Irradiations for AOP experiments were carried out using a medium pressure collimated beam system (Calgon Carbon, Pittsburg, PA) equipped with one 1 kw lamp quasi-collimated by a 6.4 cm diameter, 10 cm long cylindrical tube. The sample was held in a 150 mm diameter crystallization dish. The incident irradiance was 3.0 mw/cm 2 measured with a calibrated Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 1-5

17 International Light IL-1700 radiometer (Peabody, MA) and SED 240/W detector. The Petri Factor was 0.60 and sample depth was 4.4 cm. The average irradiance was calculated using the procedure by Bolton and Linden (Bolton and Linden, 2003) Biodegradation The experimental setup for the biodegradation study is shown in Figure 1-2. The 250 ml amber bottles held 100 ml of effluent. Each sample bottle was connected in series to two 60 ml amber glass bottles holding 50 ml of 1 N KOH each. If biodegradation of the radiolabeled molecules proceeded to complete mineralization, then 14 CO 2 would be captured in the KOH trap as carbonic acid that quickly deprotonates in the alkaline solution. Radioactivity in the KOH trap solution was the basis for concluding that CBZ is mineralized in this setup. The setup included effluent samples that either received or did not receive AOP treatment. Each sample had a corresponding abiotic control that contained the same effluent together with an activated sludge inoculum. The sludge was inactivated by adding 0.01 M sodium azide, a strong inhibitor of biological respiration. The setup also contained a blank that consisted of effluent without CBZ and activated sludge inoculum. Figure 1-2. Experimental Setup for Assessing the Biological Stability of Effluents Treated with AOP Versus Those Not Treated with AOP. The building air delivered to the system passed through a regulator assuring constant flow (1), a 0.2 micron filter removed any non-gaseous particles (2), a check valve prevented backflow (3), and a wash bottle hydrated the air to minimize sample evaporation (4). Air was delivered to the samples through a series of manifolds. Each bottle had an individual regulator valve allowing for the gaseous flow rate to be adjusted in each. 1-6

18 In the AOP-treated effluents, 1 mg/l bovine catalase was added to quench residual H 2 O 2 to prevent potential inhibition of biomass during the biodegradation assay. All samples, including the blanks, had the same concentration of H 2 O 2 and the same concentration of bovine catalase added for H 2 O 2 quenching. When H 2 O 2 gets quenched with bovine catalase, it produces oxygen. If H 2 O 2 and catalase were added only to AOP treated samples, it could potentially result in different oxygen concentrations in treated vs. untreated samples, making the treated samples more favorable for aerobic bacteria and skewing the results of the biodegradation assay in favor of the treated sample. After catalase was added, the sample was stirred and allowed to sit for 30 minutes to make sure that H 2 O 2 was degraded to levels below 0.1 mg/l. The dose of bovine catalase and the reaction time were determined in preliminary experiments. Results from one such experiment is provided in Figure 1-3 whereby bovine catalase was 0.4 mg/l and initial concentration of H 2 O 2 was 10 mg/l. In the actual biodegradation experiments, 1 mg/l of bovine catalase was used to ensure that low levels of H 2 O 2 were achieved in 30 min. Time, min ln([h 2 O 2 ]/[H 2 O 2 ] 0 ) y = x 5 6 Figure 1-3. Degradation of 10 mg/l of H2O2 with 0.4 mg/l of Bovine Catalase. Horizontal dashed line points to H2O2 concentration 0.1 mg/l. Vertical line points to the reaction time to achieve [H2O2] < 0.1 mg/l. After H 2 O 2 was degraded in AOP-treated effluents, activated sludge was added to each sample in order to achieve a final concentration of 32±1 mg VSS/L. The activated sludge bottle was shaken prior to inoculation of each sample to prevent settling and ensure a uniform starting concentration of bacteria in each sample. Sodium azide (0.01 M) was then added to control samples to inactivate the bacteria. All samples were stirred, capped and the air supply was turned on. Throughout the study, evaporation from the samples was monitored to ensure that any volume losses were taken into account. The extent of evaporation from each sample was measured by weighing each bottle at the beginning of the study and when samples were collected. The sample bottles lost up to 0.9 ml to evaporation (<1% of the total volume), and KOH traps lost up to 0.7 ml (<2% of the total volume) over 25 days. Most of the evaporation occurred in the second trap bottle, while most of the radiolabeled CO 2 was captured in the first trap bottle. Therefore, no correction for evaporation was deemed necessary. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 1-7

19 After a pre-defined period of biodegradation, samples were collected and shipped to the University at Buffalo for analysis. Before each sample was disconnected from the air supply line, it was purged with air passed at a high flow rate for several minutes to ensure that any radiolabeled CO 2 that accumulated in the head-space of the bottle would be pushed into the KOH trap. An aliquot from each collected sample and from the KOH traps were tested for radioactivity by LSC. At the same time, samples were prepared for shipping to the University at Buffalo by filtering through a 0.2 micron nylon syringe filter (Fisherbrand, Fisher Scientific, Pittsburg PA) and then reducing the volume by rotary evaporation (Buchi RE 111, Flawil, Switzerland) using a Buchi V-700 vacuum pump (150 mbar evaporation pressure) and Buchi 461 water bath set at 60 C. Rotary evaporation was chosen as a concentration method to prevent the loss of small hydrophilic by-products that have high potential for breakthrough in solid phase extraction (SPE). The top chromatogram in Figure 1-4 shows the presence of early eluting peaks characteristics of the hydrophilic by-products, while the bottom chromatogram in Figure 1-4 illustrates the loss of these peaks after passing through SPE % Radioactivity Retention time, min 100 % Radioactivity Retention time, min Figure 1-4. Oxidation Products Retained after Rotary Evaporation (top) Compared to Solid Phase Extraction (bottom). 1-8

20 CHAPTER 2.0 RESULTS 2.1 Fundamental Properties of Carbamazepine Relevant to Advanced Oxidation The pseudo-first order reaction rate constant of CBZ degradation with OH was calculated in two separate experiments using competition kinetics with a probe compound pcba as described in the methods section. The rate constant values of the two experiments were M -1 s -1 and M -1 s -1. The reaction rate constant is therefore estimated to be (1.1 ± 0.3) 10 9 M -1 s -1. Quantum yield was calculated to be and for LP and MP UV systems respectively. The MP quantum yield average is for the 200 to 300 nm range, and is about three times smaller than the low pressure quantum yield. It is possible that lower energy wavelengths do not contribute to the transformation of CBZ; a detailed wavelength dependent assessment of the quantum yield for CBZ was outside the scope of this project. 2.2 Advanced Oxidation of Nitrified Effluents Preliminary studies showed that when an effluent high in nitrate (> 9 mg/l as N) is irradiated with medium pressure (MP) UV, it creates hydroxyl radicals from nitrate while production of radicals from H 2 O 2 decreases due to a shielding effect caused by nitrate s absorbance. Therefore, at low H 2 O 2 concentrations, most of the radicals are formed by nitrate and the addition of H 2 O 2 is redundant. Therefore, higher concentrations of H 2 O 2 are required in nitrified effluents that are high in nitrate to see the increase in hydroxyl radicals beyond the steady state concentration achieved by nitrate. Figure 2-1 shows that at an H 2 O 2 concentration of 5 mg/l, no additional decay of CBZ was recorded beyond that already observed with UV treatment of the nitrified effluent alone. This indicates two things: first, no additional hydroxyl radicals were generated in BWWTP nitrified effluent when H 2 O 2 was added; and medium pressure UV treatment of nitrified effluent was sufficient to breakdown CBZ. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 2-1

21 ln[c/co] UV dose, mj/cm R² = MP UV only (slope = ) MP UV + 5 ppm H2O2 (slope = ) R² = Figure 2-1. AOP Degradation of CBZ in Nitrified Effluent Under MP UV Without H2O2 and With 5 mg/l H2O2. When higher concentrations of H 2 O 2 were evaluated, it appeared that 10 mg/l was an optimal dose that contributed to radical production and did not become a major radical scavenger. When concentrations higher than 10 mg H 2 O 2 /L were added, the contribution to the steady-state concentration of hydroxyl radicals was not proportional to the added H 2 O 2 because at higher concentrations H 2 O 2 becomes a more significant radical scavenger. The results are summarized in Figure Fraction CBZ remaining H2O2 dose: 0 mg/l 10 mg/l 20 mg/l 30 mg/l UV fluence, mj/cm 2 Figure 2-2. Fraction of CBZ Remaining (starting concentration 1.26 mg/l) in Nitrified Effluent Under MP-UV Without H2O2 and With Various Doses of H2O2. 2-2

22 2.3 Biodegradation of CBZ in Effluents With and Without AOP The experiment to assess whether AOP-treated CBZ could be biologically mineralized was conducted in duplicate using 0.2 micron filtered, non-disinfected secondary effluent from the Boulder wastewater treatment facility. Two separate effluent samples were collected by taking grab samples on days spaced one week apart. Effluent 1 was collected on a day when all four secondary clarifiers were online, and on the day when Effluent 2 was collected only two clarifiers were in operation. The water quality of the two samples is summarized in Table 2-1. Table 2-1. Boulder Wastewater Treatment Plant Effluent Quality During Two Sampling Events. Water Quality Parameter Method Used Units Effluent 1 Effluent 2 Alkalinity Hach digital titrator mg/l as CaCO ph Beckman ph meter Ammonium Nitrite Nitrate Dissolved organic carbon Total nitrogen Hach colorimetric test kit Hach colorimetric test kit Hach colorimetric test kit Shimadzu TOC analyzer Shimadzu TN analyzer mg/l as N < mg/l as N < < mg/l as N mg/l as C 7.52 Not Measured mg/l as N 17.6 Not Measured Figure 2-3 shows the results of a preliminary study that examined whether the activated sludge culture was impacted adversely by the addition of CBZ. Both SUVA 254 and nitrate concentration, normalized to the initial SUVA254 and nitrate, were used as surrogate indicators of the physiological status of the culture. Given the conditions of the experiment, endogenous conditions ensued and nitrate uptake can be interpreted as denitrification by intrafloc biomass where oxygen does not readily permeate. The results show that there was no difference in the normalized SUVA 254 and nitrate concentration either with or without CBZ. Therefore, it was concluded that CBZ did not inhibit the biomass and prior acclimation of biomass to the test conditions was not necessary. It was important to determine if AOP treatment itself resulted in mineralization of CBZ in the absence of biomass. Figure 3-4 illustrates that mineralization in the absence of biomass did not occur because all of the radioactivity remained in solution (insignificant amounts of radioactivity were found in KOH trap solutions from abiotic AOP-treated effluents, indicating an absence of 14 CO 2 ). Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 2-3

23 Normalized SUVA without CBZ with CBZ Normalized nitrate concentration without CBZ with CBZ Duration of biodegradation, days Duration of biodegradation, days Figure 2-3. Change in SUVA254 (left) and Nitrate Concentration (right) During Storage of Effluent with Activated Sludge, Both With and Without CBZ Radioactivity, CPM Pre-AOP Post-AOP Figure 2-4. Radioactivity of Effluents Before and After AOP (1800 mj/cm 2 UV Fluence and 10 mg/l H2O2 Dose) in the Absence of Activated Sludge Inoculum. In contrast, liquid scintillation analysis of biodegradation assay samples showed that a significant fraction of 14 C-CBZ was completely mineralized to CO 2 in AOP-treated effluents over the course of 25 days while no biodegradation occurred in the effluents not treated with AOP (Figure 2-5). 2.4 AOP Byproduct Formation and Biological Fate Figure 2-6 shows radiochromatograms that compare samples with and without AOP treatment. The results show that CBZ is unchanged in samples that were not exposed to AOP (pre-aop) but were exposed to activated sludge for 25 days. In contrast, the radiochromatogram of samples that were exposed to AOP (post-aop) show that some products were formed (time zero). Furthermore, after nine days exposure to activated sludge under aerobic conditions, there is a distinct loss in radioactivity associated with early (more polar) peaks. 2-4

24 Normalized radioactivity Pre-AOP sample Normalized radioactivity Pre-AOP control Normalized radioactivity Days of biodegradation Post-AOP sample Normalized radioactivity Days of biodegradation Post-AOP control Days of biodegradation Days of biodegradation Figure 2-5. Biodegradation Experimental Results Show that CBZ Was Mineralized Only in AOP Treated Effluents. The gray color represents the fraction of radioactivity present in solution due to the presence of CBZ and AOP-derived products. The black color represents the fraction of radioactivity that migrated into the KOH traps as CO2, i.e., the fraction of the 14 C-CBZ that was fully mineralized. The control represents effluents treated with sodium azide. Mass spectrometry was used to assess which compounds, with m/z from 150 to 350, were being formed by AOP, and which of those byproducts were subsequently biodegraded. As shown in Figure 2-7, CBZ (m/z 237) is biologically stable over time, but byproducts (m/z 251 and 253) were formed by AOP treatment. After 25 days of biodegradation, product peak m/z 251 disappeared and product peak m/z 253 was significantly reduced in size such that only unoxidized CBZ was present to a significant degree after 25 days. The byproducts of CBZ AOP were proposed to be the CBZ molecule where a carbonyl or a hydroxyl group has been introduced (Figure 2-8). These are common products of AOP during which the main mechanism of the contaminant transformation is the reaction between the parent molecule and hydroxyl radicals. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 2-5

25 Figure 2-6. Radiochromatogram of AOP Treated (left) and Untreated (right) Samples Before Biodegradation (top) and After Biodegradation (bottom). It has been previously hypothesized that hydroxylation of aromatic rings in pharmaceutical compounds to catechols makes the rings susceptible to cleaving by catechol dioxygenase enzymes produced by heterotrophic bacteria, such as those typically found in activated sludge (Khunjar et al., 2011). Once the ring is open the molecule becomes less stable and therefore more degradable and vulnerable to mineralization. Continued hydroxylation of the AOP byproducts m/z 251 and m/z 253 may occur and enable ring cleavage, and ultimate mineralization, for AOP-enhanced biodegradation of CBZ by activated sludge microorganisms. 2-6

26 Figure 2-7. MS Chromatogram of the AOP-Treated Effluent Before Biodegradation (top) and After Biodegradation (bottom). Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 2-7

27 Parent, m/z 237 m/z 251 m/z 253 m/z 253 Figure 2-8. Proposed Products of CBZ Advanced Oxidation. 2-8

28 CHAPTER 3.0 CONCLUSIONS The results of this study indicate that the AOP-derived oxidation products of CBZ a pharmaceutical routinely found to be recalcitrant to biodegradation at wastewater treatment plants are mineralized by activated sludge bacteria retrieved from a conventional treatment plant. 90% degradation of the parent compound was achieved using a UV/AOP treatment level of 1800 mj/cm 2 UV fluence and 10 mg/l dose of H 2 O 2. The research indicates that AOP treatment followed by a biological degradation process at wastewater treatment plants (either via engineered processes such as biofiltration or through constructed wetlands downstream of the effluent) may be able to achieve a significant level of CBZ mineralization. This result cannot be achieved by either AOP or biodegradation alone. However, some level of CBZ oxidation by UV treatment of nitrified effluents (without H 2 O 2 addition) was also shown to occur and deserves further study. The role of nitrate absorption of UV light and its relative impact on both production of hydroxyl radicals and screening of UV from H 2 O 2 should be further investigated. The outcome of this study is a significant achievement in the ongoing effort to develop methods that remove pharmaceuticals from effluents. Other recalcitrant pharmaceuticals may be vulnerable to the same fate and deserve further study. Extending this work to other recalcitrant pharmaceuticals in the future would be beneficial for improved comprehension of the process and its full-scale wastewater treatment benefits. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine 3-1

29 3-2

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