Environ Sci Pollut Res DOI 10.1007/s11356-014-2877-9
ADVANCED OXIDATION PROCESSES FOR ENVIRONMENTAL PROTECTION
Effect of Fenton treatment on the aquatic toxicity of bisphenol A in different water matrices Idil Arslan-Alaton & Ece Aytac & Kresten Ole Kusk
Received: 10 January 2014 / Accepted: 2 April 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Battery tests serve as integral tools to decide whether a treatment process is ecotoxicologically safe or not. In the present study, a battery of toxicity tests was employed to elucidate the toxicity of the potential endocrine-disrupting pollutant bisphenol A (BPA) and its advanced oxidation products. For this purpose, BPA was subjected to Fenton treatment in the growth medium of the test organisms employed as well as in real lake water. Treatment results indicated that BPA removals were fast and complete within less than a minute, whereas total organic carbon (TOC) removals were rather incomplete, speaking for the accumulation of refractory degradation products. The presence of chloride and/or natural organic matter influenced H2O2 consumption rates and the treatment performance of the Fenton’s reagent as well. The sensitivity of the selected test organisms for BPA and its Fenton treatment products in different water matrices was found in the following decreasing order: the freshwater microalgae (Pseudokirchneriella subcapitata) > the freshwater cladoceran (Daphnia magna) > marine photobacteria (Vibrio fischeri).
Keywords Bisphenol A . Battery toxicity testing . V. fischeri . D. magna . P. subcapitata . Fenton treatment . Advanced oxidation
Responsible editor: Philippe Garrigues I. Arslan-Alaton (*) : E. Aytac Environmental Engineering Department, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey e-mail: [email protected] K. O. Kusk Environmental Engineering Department, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Introduction Bisphenol A (BPA) is being predominantly used in the production of polycarbonate plastics as well as the majority of epoxy and polysulfonate resins (JRC 2008). BPA is being distributed in the environment through a number of routes, including urban wastewater discharge, wash water originating from BPA production facilities, leaching from consumer products containing BPA at hazardous waste landfill sites, residuals of particulates or dust from BPA production processes or storage facilities, as well as accidental discharge (Yamamoto et al. 2001; Fromme et al. 2002). BPA has been found to mimic the primary female sex hormone estrogen (Kang et al. 2006a) and thus categorized within a group of so-called endocrine-disrupting compounds (EDCs). Moreover, it has been reported that BPA may cause a decline in sperm counts and potentially increase the rates of hormone-related cancers, including breast, testicular, and prostate cancer (Ropero et al. 2008; Okada et al. 2008). BPA may impart teratogenic effects and defects in the reproductive tract, as well as earlier puberty in girls and obesity (Newbold et al. 2008). Regarding its physicochemical properties, BPA has a relatively low vapor pressure of 3.91×10−7 mmHg, and due to its low Henry’s law (1.0×10−11 atm m3(mol fraction)−1), volatilization from water surfaces is not expected to have an important role on its fate in the aquatic environment (JRC 2008). When released into natural waters, BPA readily adsorbs onto suspended solids and soil sediments based upon an estimated Koc (soil organic carbon-water partitioning coefficient) of 796 (JRC 2008). Hydrolysis of BPA is also negligible under ambient environmental conditions since BPA lacks functional groups being susceptible to hydrolysis (USFDA 2012). It has been postulated that biodegradation is also accepted to have minor contribution, and BPA may cause severe problems in biological activated sludge treatment systems because of its poor biodegradability and inhibitory effects on microbial
Environ Sci Pollut Res
processes (Kang et al. 2006b; Lee et al. 2008). Partial degradation may result in metabolites being more toxic than BPA itself. Several treatment methods including adsorption, membrane filtration, and ozonation have been proposed for the removal of BPA, however, generally speaking, with poor results (Zhang et al. 2006; Liu et al. 2009; Garoma et al. 2010). Undoubtedly, there is an urgent need to develop alternative treatment processes for the efficient removal of BPA and its endocrine-disrupting and/or toxic properties. Several treatability studies have already shown that advanced oxidation processes (AOPs) are more effective in the removal of EDCs than conventional treatment processes (Chiang et al. 2003; Rosenfeldt and Linden 2004; Chen et al. 2006; Ioan et al. 2007; Young et al. 2013). AOPs are based on the generation of highly reactive and hence nonselective oxidizing agents including the hydroxyl radical (HO·). One of the relatively well-known and economically acceptable AOPs is the Fenton’s reagent, which relies on the catalytic decomposition of Fe2+ and/or Fe3+ by H2O2 under acidic pH values (2– 5). The chemicals used for the Fenton’s reagent are highly abundant and easy to handle (Duesterberg et al. 2008). Before deciding for the most appropriate AOP to treat emerging pollutants, it should be considered that the efficiency and performance of these treatment processes may change dramatically when they are applied to contaminants in real water and wastewater matrices that contain significant amounts of organic (humic substances, surfactants, pesticides, etc.) as well as inorganic (carbonate, bicarbonate, chloride, nitrate, phosphate, etc.), substances that may inhibit oxidation rates dramatically (Sajiki and Yonekubo 2004; Molkenthin et al. 2013). Consequently, it is important to test the performance of AOPs under real conditions, namely in the natural environment of the target pollutant. Moreover, it should be kept in mind that during application of AOPs, there is always the possibility of forming degradation products that could potentially be more toxic/harmful than the original pollutant (Marugán et al. 2012). Hence, assessment of the ecotoxicological effects of EDCs discharged into the environment using rapid, reliable, simple, sensitive, and economic bioassays can provide critical information on the risk of BPA and its treatment products (Rizzo 2011). Traditionally, microorganisms, plants, algae, invertebrates, and fish are used for this purpose (Hernando et al. 2005). There is a significant gap in the scientific literature regarding the application of AOPs to treat endocrine-disrupting pollutants in real water and wastewater matrices as well as the use of battery tests to examine the ecotoxicological risk or safety of AOP applications. Considering the abovementioned issues, the motivation of the present study was to examine the changes in acute toxicity of BPA during the application of the Fenton’s reagent in growth media and real lake water samples. For this purpose, a series of battery tests was conducted on untreated and
Fenton-treated synthetic (growth medium) and real freshwater (lake water) samples spiked with BPA. In the battery test, representatives of the three trophic levels were considered, namely (i) the marine photobacteria Vibrio fischeri (decomposer level), (ii) the freshwater cladoceran Daphnia magna (consumer level), and (iii) the freshwater green microalgae Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum, representing the producer level). The main original aspect of the present study is the application of the Fenton’s reagent to remove BPA in the actual growth medium of the selected test organisms.
Materials and methods Reagents and supplies BPA (228 g/mol; C15H16O2; Chemical Abstract Service (CAS) No. 80-05-7; purity 99.9 %) and ferrous sulfate (FeSO4 ·7H2O; CAS No. 7782-63-0; purity 99.5 %) were purchased from Sigma-Aldrich (USA) and used as received. Analytical-grade hydrogen peroxide (H2O2; CAS No. 772284-1; 35 % w/w) and chromatographic-grade acetonitrile (CH3CN; CAS No. 75-05-8) were all obtained from Merck (Germany). BPA solutions were prepared with distilled water, the growth medium of the test organisms as well as in real lake water. Ultrapure water for the chromatographic measurements was prepared with an Arium 611UV water purification system (Sartorius AG, Germany). All other chemicals required for analytical and experimental procedures were at least of analytical grade. Real lake water samples Fenton experiments were also carried out in real freshwater that was taken from Sjælsø Lake located in Birkerød, Denmark. Sjælsø Lake serves as a drinking water reservoir for the Gentofte Municipality. Some environmental characteristics of the lake water sample are given in Table 1. Samples were stored in plastic carboys in a cool room at 4 °C prior to use; 150-nm cutoff glass microfiber filters (VWR European; Cat. No. 516-0875) and 450-nm cutoff cellulose acetate membrane syringe filters (Q-Max CA-S; Cat. No. CA250450S) were used to obtain clear supernatants prior to experiments and analyses. Fenton treatment experiments Fenton treatment experiments were conducted in 2,000-mLcapacity glass beakers. Conditions of the Fenton experiments were selected upon consideration of a related work and preliminary baseline experiments conducted with aqueous BPA solutions (Kang and Hwang 2000; Molkenthin et al. 2013).
Environ Sci Pollut Res Table 1 Environmental characterization of the raw lake water sample taken from Sjælsø Lake, Denmark
Parameter
Value
TOC TKN PO4-P Alkalinity pH
10.4 mg C/L 1.1 mg N/L 0.08 mg P/L 140 mg CaCO3/L 8.4
The initial BPA concentration was decided to enable accurate measurements by using the analytical and toxicity test procedures. The pH of the reaction solutions containing 20 mg/L of BPA was adjusted to 5.0 using 1 N NaOH and 1 or 6 N H2SO4. Then, an appropriate amount of H2O2 was added to the pHadjusted samples from a 35 % w/w stock solution to obtain a final concentration of 2.0 mM H2O2 in the reaction solution. The Fenton reaction was initiated by adding 0.4 mM Fe ions from a freshly prepared FeSO4 ·7H2O (10 %w/v) stock solution. The Fenton reaction was continued for 90 min to ensure significant removals, and samples were taken at regular time intervals for analytical examinations. The Fenton reaction was ceased by spiking the sample with 1 N NaOH to increase the pH to >10. In order to enhance Fe(OH)3 precipitation and maximize Fe2+ removal, the pH was readjusted to around neutral values (pH 7.0–7.5). The formed Fe(OH)3 flocs were removed from the reaction solution through 450-nm cutoff membrane filters prior to all measurements. The samples were analyzed for changes in BPA, total organic carbon (TOC), residual (unreacted) H2O2, and acute toxicity (EC50 values of the original BPA sample and relative changes during Fenton treatment experiments). Analytical procedures BPA was quantified by an Agilent 1100 Series HPLC equipped with a Diode-Array Detector (DAD; G1315A, Agilent Series) set at 214 nm. A C18 Symmetry column (3.9 mm×150 mm; 5 μm particle size; Waters, USA) was employed as a stationary phase, while the mobile phase was a mixture of acetonitrile/water used at a ratio of 50:50 (v/v). The flow rate and temperature of the column were set as 1.0 mL min−1 and 25 °C, respectively. The instrument detection and quantification limit for BPA (50 μL of injection volume) was calculated as 70 and 210 μg L−1, respectively. Changes in the TOC content of the samples were monitored on a Shimadzu VPCN carbon analyzer equipped with an auto-sampler and infrared detector. The TOC analyzer was periodically calibrated with standard potassium hydrogen phthalate solutions. The residual (unreacted) H2O2 was measured by using the oxo-peroxo-pyridine-2,6-dicarboxylato-vanadate (OPDV) colorimetric method in accordance with that of Tanner and Wong (1998). In order to eliminate their positive effect on
toxicity measurements, residual/unreacted H 2 O 2 was decomposed with the enzyme catalase (from Micrococcus lysodeikticus; CAS No. 9001-05-2; Fluka), respectively. For the bioassays, control samples were also prepared for catalase exactly at the concentration used to remove H2O2. Photoluminescence inhibition test with V. fischeri The acute toxicity towards the photobacterium V. fischeri was measured before and during Fenton treatment of BPA by using a commercial assay kit marketed as BioTox™ (Aboatox Oy, Finland) according to the test protocol ISO 11348-3 (2008). Prior to the test, the pH and salinity of all samples were adjusted to 7.0±0.2 and 2 % (w/v), respectively. After mixing 500 μL of untreated or Fenton-treated BPA solutions with 500 μL luminescent bacterial suspensions, the light emission after 15 min of contact time was measured at a temperature of 15 °C. Percent relative inhibition rates were calculated on the basis of a toxicant-free control. A positive control sample with potassium dichromate was also included for each test, and all bioassays were run in triplicate. Death and immobilization test with D. magna The acute toxicity test with the water flea D. magna was performed according to the ISO 6341 protocol (2010). The Danish clone of the freshwater cladoceran D. magna was isolated in Langedammen, Birkerød, in 1978 and has since then been kept as a clone in the laboratory. Under normal laboratory conditions (20 °C), the Danish clone started to reproduce when animals were 8 days old. UVP/white light transilluminator was used to count and control the number of animals in the beakers. For this test, D. magna growth medium (called “M1 medium”) was used as the dilution water. The test was performed with animals less than 24 h old which were exposed to various concentrations of the test substance for up to 48 h. All studies were conducted at 20±2 °C and pH 7.8± 0.2 with a darkness period, without external aeration and feeding. During the test, dissolved oxygen (≥2 mg O2/L) and pH were measured in the control and all test samples. After 24 and 48 h, the number of dead and/or immobilized animals was counted, and percent mortality/immobilization rates were reported. Growth inhibition test with P. subcapitata The algal growth inhibition test was carried out according to the ISO 8692 test protocol (2004). The green microalgae P. subcapitata was derived from the algal culture collection at the Norwegian Institute of Water Research (NIVA) located in Oslo. For this test, synthetic freshwater medium (called “M2 medium”) was used as the dilution water. The preculture was set up 3 days before the start of the bioassay to secure
Environ Sci Pollut Res 35 2 % w/v NaCl medium
M1 medium
M2 medium
Lake water
30 25 TOC (mg/L)
exponential growth in the inoculum culture. The cell density of the cultures was measured on the Coulter Multisizer 4 (Beckman, USA). The flasks used in the measurements contained originally 104 cells/mL in average, with 25 mL of each selected concentration. Three replicates were prepared containing 4 mL of each concentration. The replicates were placed in an algal growth chamber under continuous fluorescent illumination and incubated at 22±1 °C and pH 8±0.2. At the start and after 24 and 48 h, the cell density in the acetoneextracted blind sample and test replicates were measured at 420 nm on a Cary Eclipse Fluorescence spectrophotometer (Agilent Technologies, USA). The measured fluorescence (relative units) was used directly as the biomass parameter to calculate growth rates (in d−1) and percent relative growth inhibitions.
20 15 10 5 0 0
10
20
30
40
50
60
70
80
90
Fenton Treatment Time (min)
Fig. 1 Changes in TOC abatements during Fenton treatment of 20 mg/L BPA in different growth media and real lake water (TOC, 10 mg/L; TKN, 1 mg/L; PO4-P40 %) for P. subcapitata throughout Fenton treatment. At the end of Fenton treatment, growth inhibition was still 46 and 54 % in the M2 medium and lake water, respectively. Growth inhibition rates were found only slightly higher for Fenton treatment of BPA in the real lake water. Results revealed that P. subcapitata was more sensitive to BPA oxidation products during application of Fenton treatment than the other two test organisms.
40
Conclusions 20
0 0
5 30 60 Fenton Treatment Time (min)
90
Fig. 3 Percent death/immobilization rates obtained during Fenton treatment of 20 mg/L BPA in the D. magna growth (M1) medium (incubation periods 24 and 48 h)
BPA has been reported as a reproductive, developmental, and systemic toxicant and weakly estrogenic according to animal studies. There is a question mark about its potential negative impact particularly on children’s and pregnant women’s health and the environment. The present study was aimed at exploring the effect of Fenton treatment on the changes in the toxic effect of BPA. Fenton treatment experiments and bioassays
Environ Sci Pollut Res
were conducted in the growth medium of the selected test organisms and real lake water samples by employing a battery test that involved freshwater and marine organisms from different trophic levels. Fenton treatment experiments indicated that BPA removal was very rapid and complete under all studied reaction conditions. However, TOC removal efficiencies were relatively poor and incomplete due to poor degradation of oxidation products. Treatment results were affected by the available H2O2, type of the growth medium, and the real lake water constituents. TOC removal efficiencies obtained for BPA in different matrices ranged between 22 and 62 % depending on the composition of the growth medium and lake water. Although H2O2 consumption rates were significantly inhibited in the presence of chloride, BPA degradation and mineralization were not seriously affected. TOC removals were significantly retarded in the growth medium of P. subcapitata (containing EDTA complexing agent and alkalinity) and real lake water sample (having a TOC of 10.4 mg/L and significant alkalinity). Acute toxicity test results indicated that the percent relative luminescence inhibition of the photobacteria V. fischeri could be significantly reduced during Fenton treatment in the 2 %w/ v NaCl medium, parallel to BPA abatement. The acute toxicity results obtained using D. magna demonstrated that complete detoxification could be achieved at the later stages of Fenton treatment. The growth inhibition test conducted with the microalgae P. subcapitata indicated that the percent relative inhibition of the original BPA solution in the algal growth medium and lake water being 100 % dropped to 55–60 and 30–45 % (24 h of incubation time) and to 40–55 and 40–65 % (48 h of incubation time) during Fenton treatment. These findings revealed that a complete detoxification could not be achieved during Fenton treatment of BPA samples according to the results of the algal growth inhibition tests. Apparently, BPA was not only the source of toxicity but also its degradation products. In conclusion, the Fenton’s reagent appeared to be kinetically very attractive to remove BPA from aqueous solution and could lead to fair TOC removals even in real surface water. Overall speaking, it could be demonstrated that the most sensitive test organism towards Fenton degradation (advanced oxidation) products was the microalgae P. subcapitata, whereas the photobacteria V. fischeri was the least sensitive organism among the selected test organisms. Further experiments are currently underway to identify oxidation products (degradation intermediates) of BPA during Fenton treatment to establish relationships between aquatic toxicity and early-stage oxidation products. In order to observe the toxicological effects of BPA during the application of AOPs, it is highly recommended to prefer to use comprehensive battery tests due to the fact that the sensitivity of aquatic test organisms varies significantly according to the type of pollutant and treatment process.
Acknowledgments The authors acknowledge the cooperation and financial support of Istanbul Technical University and the Technical University of Denmark under the Erasmus-Socrates Program.
References Buxton GU, Greenstock CL, Helman WP, Ross AB (1988) Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (OH·/O·−) in aqueous solution. J Phys Chem Ref Data 17:513–886 Chen PJ, Linden KG, Hinton DE, Kashiwada S, Rosenfeldt EJ, Kullman SW (2006) Biological assessment of bisphenol A degradation in water following direct photolysis and UV advanced oxidation. Chemosphere 65:1094–1102 Chiang K, Lim TM, Tsen L, Lee CC (2003) Photocatalytic degradation and mineralization of bisphenol A by TiO2 and platinized TiO2. Appl Catal A Gen 261:225–237 De Laat J, Le GT, Legube B (2004) A comparative study of the effects of chloride, sulfate and nitrate ions on the rates of decomposition of H2O2 and organic compounds by Fe(II)/H2O2 and Fe(III)/H2O2. Chemosphere 55:715–723 Duesterberg CK, Mylon ES, Waite TD (2008) pH effects on ironcatalyzed oxidation using Fenton’s reagent. Environ Sci Technol 42:8522–8527 European Commission's Joint Research Centre (2008) European Union updated risk assessment report. Bisphenol A, CAS No: 80-05-7. JRC, Institute for Health and Consumer Protection (IHCP), European Chemicals Bureau (ECB), Ispra Farrè M, Barcelò D (2003) Toxicity testing of wastewater and sewage sludge by biosensors, bioassays and chemical analysis. Trends Anal Chem 22:299–310 Fromme H, Kuchler T, Otto T, Pilz K, Muller J, Wenzel A (2002) Occurrence of phthalates and bisphenol A and F in the environment. Water Res 36:1429–1438 Frontistis Z, Daskalaki VM, Katsaounis A, Poulios I, Mantzavinos D (2011) Electrochemical enhancement of solar photocatalysis: degradation of endocrine disruptor bisphenol-A on Ti/TiO2 films. Water Res 45:2996–3004 Garoma T, Matsumoto SA, Wu Y, Klinger R (2010) Removal of Bisphenol A and its reaction-intermediates from aqueous solution by ozonation. Ozone Sci Eng 32:338–343 Hernando MD, Fernàndez-Alba AR, Tauler R, Barcelò D (2005) Toxicity assays applied to wastewater treatment. Talanta 65:358–366 Ioan I, Wilson S, Lundanes E, Neculai A (2007) Comparison of Fenton and sono-Fenton bisphenol A degradation. J Hazard Mater 142: 559–563 Isidori M, Lavorgna M, Nardelli A, Parrella A (2003) Toxicity identification evaluation of leachates from municipal solid waste landfills: a multispecies approach. Chemosphere 52:85–94 ISO 11348-3 (2008) Water quality: determination of the inhibitory effect of water samples on the light emission of Vibrio fischeri (luminescent bacteria test). Part 3: method using freeze-dried bacteria. International Organisation for Standardization, Geneva ISO 6341 (2010) Water quality: determination of the inhibition of the mobility of Daphnia magna Straus (cladocera, crustacea): acute toxicity test. International Organisation for Standardization, Geneva ISO 8692 (2004) Water quality: fresh water algal growth inhibition test with unicellular green algae. International Organisation for Standardization, Geneva Kang YW, Hwang K (2000) Effect of reaction conditions on the oxidation efficiency in the Fenton process. Water Res 10:2786–2790 Kang JH, Kondo F, Katayama Y (2006a) Human exposure to bisphenol A. Toxicology 226:79–89
Environ Sci Pollut Res Kang JH, Katayama Y, Kondo F (2006b) Biodegradation or metabolism of bisphenol A: from microorganisms to mammals. Toxicology 217: 81–90 Kiwi J, Lopez A, Nadtochenko V (2000) Mechanism and kinetics of the OH-radical intervention during Fenton oxidation in the presence of a significant amount of radical scavenger (Cl−). Environ Sci Technol 34:2162–2168 Lee J, Lee BC, Ra JS, Cho J, Kim IS, Chang NI, Kim HK, Kim SD (2008) Comparison of the removal efficiency of endocrine disrupting compounds in pilot scale sewage treatment processes. Chemosphere 71:1582–1592 Lipczynska-Kochany E, Sprah G, Harms S (1995) Influence of some groundwater and surface waters on the degradation of 4chlorophenol by the Fenton reaction. Chemosphere 30:9–20 Liu G, Ma J, Li X, Qin Q (2009) Adsorption of bisphenol A from aqueous solution onto activated carbons with different modification treatments. J Hazard Mater 164:1275–1280 Marugán J, Bru D, Pablos C, Catalá M (2012) Comparative evaluation of acute toxicity by Vibrio fischeri and fern spore based bioassays in the follow-up of toxic chemicals degradation by photocatalysis. J Hazard Mater 214:117–122 Molkenthin M, Olmez-Hanci T, Jekel MR, Arslan-Alaton I (2013) PhotoFenton-like treatment of BPA: effect of UV light source and water matrix on toxicity and transformation products. Water Res 47:5052– 5064 Neta P, Huie RE, Ross AB (1988) Rate constants for reactions for inorganic radicals in aqueous solution. J Phys Chem Ref Data 17: 1027–1247 Newbold RR, Padilla-Banks E, Jefferson WN, Heindel JJ (2008) Effects of endocrine disruptors on obesity. Int J Androl 31:201–207 Okada H, Tokunaga T, Liu X, Takayanagi S, Matsushima A, Shimohigashi Y (2008) Direct evidence revealing structural
elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma. Environ Health Perspect 116:32–38 Parvez S, Venkataraman C, Mukherji S (2006) A review on advantages of implementing luminescence inhibition test (Vibrio fischeri) for acute toxicity prediction of chemicals. Environ Int 32:265–268 Rizzo L (2011) Bioassays as a tool for evaluating advanced oxidation processes in water and wastewater treatment. Water Res 45:4311– 4340 Ropero AB, Alonso-Magdalena P, Garcia-Garcia E, Ripoll C, Fuentes E, Nadal A (2008) Bisphenol-A disruption of the endocrine pancreas and blood glucose homeostasis. Int J Androl 31:194–199 Rosenfeldt E, Linden KG (2004) Degradation of endocrine disrupting chemicals bisphenol A, ethinyl estradiol, and estradiol during UV photolysis and advanced oxidation processes. Environ Sci Technol 38:5476–5483 Sajiki A, Yonekubo J (2004) Inhibition of seawater on bisphenol A (BPA) degradation by Fenton reagents. Environ Int 30:145–150 Tanner PA, Wong AYS (1998) Spectrophotometric determination of hydrogen peroxide in rainwater. Anal Chim Acta 370:279–287 USFDA (2012) The United States Food and Drug Administration. FDA continues to study BPA: consumer updates. Retrieved 4 April 2013, Silverspring, MD Yamamoto T, Yasuhara A, Shiraishi H, Nakasugi O (2001) Bisphenol A in hazardous waste landfill leachates. Chemosphere 42:415– 418 Young T, Geng M, Lin L, Thagard SM (2013) Oxidative degradation of Bisphenol A: a comparison between Fenton reagent, UV, UV/H2O2 and ultrasound. J Adv Oxid Technol 16:89–101 Zhang Y, Causserand C, Aimar P, Cravedi JP (2006) Removal of bisphenol A by a nanofiltration membrane in view of drinking water production. Water Res 40:3793–3799
ADVANCED OXIDATION PROCESSES FOR ENVIRONMENTAL PROTECTION
Effect of Fenton treatment on the aquatic toxicity of bisphenol A in different water matrices Idil Arslan-Alaton & Ece Aytac & Kresten Ole Kusk
Received: 10 January 2014 / Accepted: 2 April 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Battery tests serve as integral tools to decide whether a treatment process is ecotoxicologically safe or not. In the present study, a battery of toxicity tests was employed to elucidate the toxicity of the potential endocrine-disrupting pollutant bisphenol A (BPA) and its advanced oxidation products. For this purpose, BPA was subjected to Fenton treatment in the growth medium of the test organisms employed as well as in real lake water. Treatment results indicated that BPA removals were fast and complete within less than a minute, whereas total organic carbon (TOC) removals were rather incomplete, speaking for the accumulation of refractory degradation products. The presence of chloride and/or natural organic matter influenced H2O2 consumption rates and the treatment performance of the Fenton’s reagent as well. The sensitivity of the selected test organisms for BPA and its Fenton treatment products in different water matrices was found in the following decreasing order: the freshwater microalgae (Pseudokirchneriella subcapitata) > the freshwater cladoceran (Daphnia magna) > marine photobacteria (Vibrio fischeri).
Keywords Bisphenol A . Battery toxicity testing . V. fischeri . D. magna . P. subcapitata . Fenton treatment . Advanced oxidation
Responsible editor: Philippe Garrigues I. Arslan-Alaton (*) : E. Aytac Environmental Engineering Department, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey e-mail: [email protected] K. O. Kusk Environmental Engineering Department, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Introduction Bisphenol A (BPA) is being predominantly used in the production of polycarbonate plastics as well as the majority of epoxy and polysulfonate resins (JRC 2008). BPA is being distributed in the environment through a number of routes, including urban wastewater discharge, wash water originating from BPA production facilities, leaching from consumer products containing BPA at hazardous waste landfill sites, residuals of particulates or dust from BPA production processes or storage facilities, as well as accidental discharge (Yamamoto et al. 2001; Fromme et al. 2002). BPA has been found to mimic the primary female sex hormone estrogen (Kang et al. 2006a) and thus categorized within a group of so-called endocrine-disrupting compounds (EDCs). Moreover, it has been reported that BPA may cause a decline in sperm counts and potentially increase the rates of hormone-related cancers, including breast, testicular, and prostate cancer (Ropero et al. 2008; Okada et al. 2008). BPA may impart teratogenic effects and defects in the reproductive tract, as well as earlier puberty in girls and obesity (Newbold et al. 2008). Regarding its physicochemical properties, BPA has a relatively low vapor pressure of 3.91×10−7 mmHg, and due to its low Henry’s law (1.0×10−11 atm m3(mol fraction)−1), volatilization from water surfaces is not expected to have an important role on its fate in the aquatic environment (JRC 2008). When released into natural waters, BPA readily adsorbs onto suspended solids and soil sediments based upon an estimated Koc (soil organic carbon-water partitioning coefficient) of 796 (JRC 2008). Hydrolysis of BPA is also negligible under ambient environmental conditions since BPA lacks functional groups being susceptible to hydrolysis (USFDA 2012). It has been postulated that biodegradation is also accepted to have minor contribution, and BPA may cause severe problems in biological activated sludge treatment systems because of its poor biodegradability and inhibitory effects on microbial
Environ Sci Pollut Res
processes (Kang et al. 2006b; Lee et al. 2008). Partial degradation may result in metabolites being more toxic than BPA itself. Several treatment methods including adsorption, membrane filtration, and ozonation have been proposed for the removal of BPA, however, generally speaking, with poor results (Zhang et al. 2006; Liu et al. 2009; Garoma et al. 2010). Undoubtedly, there is an urgent need to develop alternative treatment processes for the efficient removal of BPA and its endocrine-disrupting and/or toxic properties. Several treatability studies have already shown that advanced oxidation processes (AOPs) are more effective in the removal of EDCs than conventional treatment processes (Chiang et al. 2003; Rosenfeldt and Linden 2004; Chen et al. 2006; Ioan et al. 2007; Young et al. 2013). AOPs are based on the generation of highly reactive and hence nonselective oxidizing agents including the hydroxyl radical (HO·). One of the relatively well-known and economically acceptable AOPs is the Fenton’s reagent, which relies on the catalytic decomposition of Fe2+ and/or Fe3+ by H2O2 under acidic pH values (2– 5). The chemicals used for the Fenton’s reagent are highly abundant and easy to handle (Duesterberg et al. 2008). Before deciding for the most appropriate AOP to treat emerging pollutants, it should be considered that the efficiency and performance of these treatment processes may change dramatically when they are applied to contaminants in real water and wastewater matrices that contain significant amounts of organic (humic substances, surfactants, pesticides, etc.) as well as inorganic (carbonate, bicarbonate, chloride, nitrate, phosphate, etc.), substances that may inhibit oxidation rates dramatically (Sajiki and Yonekubo 2004; Molkenthin et al. 2013). Consequently, it is important to test the performance of AOPs under real conditions, namely in the natural environment of the target pollutant. Moreover, it should be kept in mind that during application of AOPs, there is always the possibility of forming degradation products that could potentially be more toxic/harmful than the original pollutant (Marugán et al. 2012). Hence, assessment of the ecotoxicological effects of EDCs discharged into the environment using rapid, reliable, simple, sensitive, and economic bioassays can provide critical information on the risk of BPA and its treatment products (Rizzo 2011). Traditionally, microorganisms, plants, algae, invertebrates, and fish are used for this purpose (Hernando et al. 2005). There is a significant gap in the scientific literature regarding the application of AOPs to treat endocrine-disrupting pollutants in real water and wastewater matrices as well as the use of battery tests to examine the ecotoxicological risk or safety of AOP applications. Considering the abovementioned issues, the motivation of the present study was to examine the changes in acute toxicity of BPA during the application of the Fenton’s reagent in growth media and real lake water samples. For this purpose, a series of battery tests was conducted on untreated and
Fenton-treated synthetic (growth medium) and real freshwater (lake water) samples spiked with BPA. In the battery test, representatives of the three trophic levels were considered, namely (i) the marine photobacteria Vibrio fischeri (decomposer level), (ii) the freshwater cladoceran Daphnia magna (consumer level), and (iii) the freshwater green microalgae Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum, representing the producer level). The main original aspect of the present study is the application of the Fenton’s reagent to remove BPA in the actual growth medium of the selected test organisms.
Materials and methods Reagents and supplies BPA (228 g/mol; C15H16O2; Chemical Abstract Service (CAS) No. 80-05-7; purity 99.9 %) and ferrous sulfate (FeSO4 ·7H2O; CAS No. 7782-63-0; purity 99.5 %) were purchased from Sigma-Aldrich (USA) and used as received. Analytical-grade hydrogen peroxide (H2O2; CAS No. 772284-1; 35 % w/w) and chromatographic-grade acetonitrile (CH3CN; CAS No. 75-05-8) were all obtained from Merck (Germany). BPA solutions were prepared with distilled water, the growth medium of the test organisms as well as in real lake water. Ultrapure water for the chromatographic measurements was prepared with an Arium 611UV water purification system (Sartorius AG, Germany). All other chemicals required for analytical and experimental procedures were at least of analytical grade. Real lake water samples Fenton experiments were also carried out in real freshwater that was taken from Sjælsø Lake located in Birkerød, Denmark. Sjælsø Lake serves as a drinking water reservoir for the Gentofte Municipality. Some environmental characteristics of the lake water sample are given in Table 1. Samples were stored in plastic carboys in a cool room at 4 °C prior to use; 150-nm cutoff glass microfiber filters (VWR European; Cat. No. 516-0875) and 450-nm cutoff cellulose acetate membrane syringe filters (Q-Max CA-S; Cat. No. CA250450S) were used to obtain clear supernatants prior to experiments and analyses. Fenton treatment experiments Fenton treatment experiments were conducted in 2,000-mLcapacity glass beakers. Conditions of the Fenton experiments were selected upon consideration of a related work and preliminary baseline experiments conducted with aqueous BPA solutions (Kang and Hwang 2000; Molkenthin et al. 2013).
Environ Sci Pollut Res Table 1 Environmental characterization of the raw lake water sample taken from Sjælsø Lake, Denmark
Parameter
Value
TOC TKN PO4-P Alkalinity pH
10.4 mg C/L 1.1 mg N/L 0.08 mg P/L 140 mg CaCO3/L 8.4
The initial BPA concentration was decided to enable accurate measurements by using the analytical and toxicity test procedures. The pH of the reaction solutions containing 20 mg/L of BPA was adjusted to 5.0 using 1 N NaOH and 1 or 6 N H2SO4. Then, an appropriate amount of H2O2 was added to the pHadjusted samples from a 35 % w/w stock solution to obtain a final concentration of 2.0 mM H2O2 in the reaction solution. The Fenton reaction was initiated by adding 0.4 mM Fe ions from a freshly prepared FeSO4 ·7H2O (10 %w/v) stock solution. The Fenton reaction was continued for 90 min to ensure significant removals, and samples were taken at regular time intervals for analytical examinations. The Fenton reaction was ceased by spiking the sample with 1 N NaOH to increase the pH to >10. In order to enhance Fe(OH)3 precipitation and maximize Fe2+ removal, the pH was readjusted to around neutral values (pH 7.0–7.5). The formed Fe(OH)3 flocs were removed from the reaction solution through 450-nm cutoff membrane filters prior to all measurements. The samples were analyzed for changes in BPA, total organic carbon (TOC), residual (unreacted) H2O2, and acute toxicity (EC50 values of the original BPA sample and relative changes during Fenton treatment experiments). Analytical procedures BPA was quantified by an Agilent 1100 Series HPLC equipped with a Diode-Array Detector (DAD; G1315A, Agilent Series) set at 214 nm. A C18 Symmetry column (3.9 mm×150 mm; 5 μm particle size; Waters, USA) was employed as a stationary phase, while the mobile phase was a mixture of acetonitrile/water used at a ratio of 50:50 (v/v). The flow rate and temperature of the column were set as 1.0 mL min−1 and 25 °C, respectively. The instrument detection and quantification limit for BPA (50 μL of injection volume) was calculated as 70 and 210 μg L−1, respectively. Changes in the TOC content of the samples were monitored on a Shimadzu VPCN carbon analyzer equipped with an auto-sampler and infrared detector. The TOC analyzer was periodically calibrated with standard potassium hydrogen phthalate solutions. The residual (unreacted) H2O2 was measured by using the oxo-peroxo-pyridine-2,6-dicarboxylato-vanadate (OPDV) colorimetric method in accordance with that of Tanner and Wong (1998). In order to eliminate their positive effect on
toxicity measurements, residual/unreacted H 2 O 2 was decomposed with the enzyme catalase (from Micrococcus lysodeikticus; CAS No. 9001-05-2; Fluka), respectively. For the bioassays, control samples were also prepared for catalase exactly at the concentration used to remove H2O2. Photoluminescence inhibition test with V. fischeri The acute toxicity towards the photobacterium V. fischeri was measured before and during Fenton treatment of BPA by using a commercial assay kit marketed as BioTox™ (Aboatox Oy, Finland) according to the test protocol ISO 11348-3 (2008). Prior to the test, the pH and salinity of all samples were adjusted to 7.0±0.2 and 2 % (w/v), respectively. After mixing 500 μL of untreated or Fenton-treated BPA solutions with 500 μL luminescent bacterial suspensions, the light emission after 15 min of contact time was measured at a temperature of 15 °C. Percent relative inhibition rates were calculated on the basis of a toxicant-free control. A positive control sample with potassium dichromate was also included for each test, and all bioassays were run in triplicate. Death and immobilization test with D. magna The acute toxicity test with the water flea D. magna was performed according to the ISO 6341 protocol (2010). The Danish clone of the freshwater cladoceran D. magna was isolated in Langedammen, Birkerød, in 1978 and has since then been kept as a clone in the laboratory. Under normal laboratory conditions (20 °C), the Danish clone started to reproduce when animals were 8 days old. UVP/white light transilluminator was used to count and control the number of animals in the beakers. For this test, D. magna growth medium (called “M1 medium”) was used as the dilution water. The test was performed with animals less than 24 h old which were exposed to various concentrations of the test substance for up to 48 h. All studies were conducted at 20±2 °C and pH 7.8± 0.2 with a darkness period, without external aeration and feeding. During the test, dissolved oxygen (≥2 mg O2/L) and pH were measured in the control and all test samples. After 24 and 48 h, the number of dead and/or immobilized animals was counted, and percent mortality/immobilization rates were reported. Growth inhibition test with P. subcapitata The algal growth inhibition test was carried out according to the ISO 8692 test protocol (2004). The green microalgae P. subcapitata was derived from the algal culture collection at the Norwegian Institute of Water Research (NIVA) located in Oslo. For this test, synthetic freshwater medium (called “M2 medium”) was used as the dilution water. The preculture was set up 3 days before the start of the bioassay to secure
Environ Sci Pollut Res 35 2 % w/v NaCl medium
M1 medium
M2 medium
Lake water
30 25 TOC (mg/L)
exponential growth in the inoculum culture. The cell density of the cultures was measured on the Coulter Multisizer 4 (Beckman, USA). The flasks used in the measurements contained originally 104 cells/mL in average, with 25 mL of each selected concentration. Three replicates were prepared containing 4 mL of each concentration. The replicates were placed in an algal growth chamber under continuous fluorescent illumination and incubated at 22±1 °C and pH 8±0.2. At the start and after 24 and 48 h, the cell density in the acetoneextracted blind sample and test replicates were measured at 420 nm on a Cary Eclipse Fluorescence spectrophotometer (Agilent Technologies, USA). The measured fluorescence (relative units) was used directly as the biomass parameter to calculate growth rates (in d−1) and percent relative growth inhibitions.
20 15 10 5 0 0
10
20
30
40
50
60
70
80
90
Fenton Treatment Time (min)
Fig. 1 Changes in TOC abatements during Fenton treatment of 20 mg/L BPA in different growth media and real lake water (TOC, 10 mg/L; TKN, 1 mg/L; PO4-P40 %) for P. subcapitata throughout Fenton treatment. At the end of Fenton treatment, growth inhibition was still 46 and 54 % in the M2 medium and lake water, respectively. Growth inhibition rates were found only slightly higher for Fenton treatment of BPA in the real lake water. Results revealed that P. subcapitata was more sensitive to BPA oxidation products during application of Fenton treatment than the other two test organisms.
40
Conclusions 20
0 0
5 30 60 Fenton Treatment Time (min)
90
Fig. 3 Percent death/immobilization rates obtained during Fenton treatment of 20 mg/L BPA in the D. magna growth (M1) medium (incubation periods 24 and 48 h)
BPA has been reported as a reproductive, developmental, and systemic toxicant and weakly estrogenic according to animal studies. There is a question mark about its potential negative impact particularly on children’s and pregnant women’s health and the environment. The present study was aimed at exploring the effect of Fenton treatment on the changes in the toxic effect of BPA. Fenton treatment experiments and bioassays
Environ Sci Pollut Res
were conducted in the growth medium of the selected test organisms and real lake water samples by employing a battery test that involved freshwater and marine organisms from different trophic levels. Fenton treatment experiments indicated that BPA removal was very rapid and complete under all studied reaction conditions. However, TOC removal efficiencies were relatively poor and incomplete due to poor degradation of oxidation products. Treatment results were affected by the available H2O2, type of the growth medium, and the real lake water constituents. TOC removal efficiencies obtained for BPA in different matrices ranged between 22 and 62 % depending on the composition of the growth medium and lake water. Although H2O2 consumption rates were significantly inhibited in the presence of chloride, BPA degradation and mineralization were not seriously affected. TOC removals were significantly retarded in the growth medium of P. subcapitata (containing EDTA complexing agent and alkalinity) and real lake water sample (having a TOC of 10.4 mg/L and significant alkalinity). Acute toxicity test results indicated that the percent relative luminescence inhibition of the photobacteria V. fischeri could be significantly reduced during Fenton treatment in the 2 %w/ v NaCl medium, parallel to BPA abatement. The acute toxicity results obtained using D. magna demonstrated that complete detoxification could be achieved at the later stages of Fenton treatment. The growth inhibition test conducted with the microalgae P. subcapitata indicated that the percent relative inhibition of the original BPA solution in the algal growth medium and lake water being 100 % dropped to 55–60 and 30–45 % (24 h of incubation time) and to 40–55 and 40–65 % (48 h of incubation time) during Fenton treatment. These findings revealed that a complete detoxification could not be achieved during Fenton treatment of BPA samples according to the results of the algal growth inhibition tests. Apparently, BPA was not only the source of toxicity but also its degradation products. In conclusion, the Fenton’s reagent appeared to be kinetically very attractive to remove BPA from aqueous solution and could lead to fair TOC removals even in real surface water. Overall speaking, it could be demonstrated that the most sensitive test organism towards Fenton degradation (advanced oxidation) products was the microalgae P. subcapitata, whereas the photobacteria V. fischeri was the least sensitive organism among the selected test organisms. Further experiments are currently underway to identify oxidation products (degradation intermediates) of BPA during Fenton treatment to establish relationships between aquatic toxicity and early-stage oxidation products. In order to observe the toxicological effects of BPA during the application of AOPs, it is highly recommended to prefer to use comprehensive battery tests due to the fact that the sensitivity of aquatic test organisms varies significantly according to the type of pollutant and treatment process.
Acknowledgments The authors acknowledge the cooperation and financial support of Istanbul Technical University and the Technical University of Denmark under the Erasmus-Socrates Program.
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