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Treatment of wastewater having estrogen activity by ionizing radiation
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Radiation Physics and Chemistry 76 (2007) 699–706 www.elsevier.com/locate/radphyschem
Treatment of wastewater having estrogen activity by ionizing radiation Atsushi Kimuraa,c,, Mitsumasa Taguchia,c, Yoshimi Ohtanib, Yoshitaka Shimadab, Hiroshi Hiratsukac, Takuji Kojimaa,c a Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki-shi, Gunma 370-1292, Japan Gunma Prefectual Institute of Public Health and Environmental Sciences, 378 Kamioki-machi, Maebashi-shi, Gunma 371-0052, Japan c Gunma University, 1-5-1 Tenjin-cho, Kiryu-shi, Gunma 376-8515, Japan
b
Received 21 March 2006; accepted 7 April 2006
Abstract Decomposition of endocrine disrupting chemicals (EDCs) in wastewater was investigated by use of 60Co g-ray. Estrogen activities of wastewaters were estimated by the yeast two-hybrid assay based on human or medaka estrogen receptors. The dose required for the elimination of estrogen activity of wastewater below 1 ng dm3 was about 200 Gy (J kg1). The elimination dose of the estrogen activity depended on the amounts of total organic carbons in wastewater. The economic cost of the treatment process of EDCs using electron beam was estimated at 17 yen m3. r 2006 Elsevier Ltd. All rights reserved. Keywords: Endocrine disrupting chemicals; Wastewater;
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Co g-rays; Yeast two-hybrid assay; Total organic carbon; Economic cost
1. Introduction Environmental pollution by toxic and persistent organic chemicals is widely spread. Some of such chemicals that mimic a natural hormone or disrupt endocrine system in livings to give ill effects are so-called endocrine disrupting chemicals (EDCs) (Colborn et al., 1996). The endocrine disrupting properties of the EDCs were investigated by the cell proliferation bioassay in the 1990s (Soto et al., 1991; Sumpter and Jobling, 1995). Monitoring and screening tests of EDCs have been carried out from the latter half of the 1990s in Japan (Ministry of the Environment, Japan, 1998). Corresponding author. Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki-shi, Gunma 370-1292, Japan. E-mail address: [email protected] (A. Kimura).
17b-estradiol (E2: 1,3,5(10)-estratriene-3,17b-diol) is a natural chemical having the highest estrogen activity in water-environment and draws much attention as one of the EDCs (Routledge and Sumpter, 1996, 1997; Routledge et al., 1998; Sumpter and Jobling, 1995). p-Nonylphenols (NPs), 2,2-bis-(4-hydroxyphenyl)-propane and tert-octylphenol were definitely recognized as EDCs (Ministry of the Environment, Japan, 2001). Treatment of EDCs already released into waterenvironment has been attempted by the activated sludge system, and a result of this system is found to be insufficient to eliminate them. Advanced oxidation technologies such as ozolysis, ozone–UV system, ozone–hydrogen peroxide system, photocatalytic processes and radiolysis have been actively studied to achieve complete elimination of persistent organic
0969-806X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2006.04.005
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A. Kimura et al. / Radiation Physics and Chemistry 76 (2007) 699–706
compounds (Boye et al., 2002; Getoff, 1996, 2002; He et al., 2002; Jun et al., 2006; Ku et al., 1997; Liu et al., 2004; Mezyk et al., 2004; Nakashima et al., 2002; Ohko et al., 2001; Winarno and Getoff, 2002). However, the commercial plant based on these methods was not applied since the reactions of oxidation species with the EDCs have not been clearly understood for real-scale treatment. In the series of our research work, hydroxyl radicals generated in water by 60Co g-rays are useful for the decomposition of trace amounts of EDCs (Kimura et al., 2004a, b, 2006). The E2 concentration initially at 1.8 nmol dm3 in water decreases lower than the detection level of LC-MS (o 0.1 nmol dm3) at a dose of 10 Gy but ‘‘the estrogen activity’’ of the E2 solution is not eliminated up to 50 Gy, in other words the decomposition products from E2 have also ‘‘the estrogen activity’’. ‘‘The estrogen activity’’ of chemicals is the cross reactivity of chemicals with the estrogen receptor, and E2 is used as a standard samples of the bioassay because of its 100% cross reactivity. NPs, which exhibit one of the highest estrogen activity among artificial chemicals, have about 0.1% of the cross reactivity with the estrogen receptor. NPs are also decomposed by radiation-induced hydroxyl radicals to produce two OHadducts ascribed to p-nonylcatechol and 1-(p-hydroxyphenyl)-1-nonanol. We showed that irradiation products also have higher estrogen activity than NPs by use of the yeast two-hybrid assay. Estrogen activities of the NP solution with an initial concentration of 20 mmol dm3 were also eliminated at 5000 Gy. Now, our research is in the stage to examine whether the ionizing radiation is applicable or not to the treatment of the EDCs in wastewater as the advanced oxidation technologies. Treatment of real wastewater having the estrogen activity was studied by use of g-ray irradiation in the present paper. Estrogen activity of the wastewater was analyzed by the yeast two-hybrid assay, which can estimate estrogen activities using human estrogen receptor (hERa) and medaka estrogen receptor (mERa). The hERa has a high reactivity with estrogenic compounds such as estrone, E2 and estriol released by animals. The mERa reacts not only with the estrogenic compounds but also artificial EDCs such as NPs. The elimination rate of the estrogen activity of the wastewater by radiation-induced hydroxyl radicals was lower than that of pure water. E2 and NPs were dissolved into the wastewaters having no estrogen activity, and then used as the model wastewater. The decomposition efficiencies of E2 or NPs were found to depend on the amount of total organic carbon (TOC) in their solutions, which were obtained from the decomposition curves of them in model wastewater by g-ray irradiation. These results enable to estimate doses for essential treatment of EDCs in wastewater.
2. Experimental 2.1. Sample preparation and irradiation Real wastewater samples were obtained from the three different secondary effluents of water treatment plants with the activated sludge system. The amounts of TOC of these samples were 7.25, 8.66 and 25.4 mg dm3, and the pH values were 8.24, 8.28 and 7.49, respectively. Each sample at 0.1 dm3 was used after filtration with a paper (Whatman, Qualitative Circles 150 mm f) to remove dusts. A model wastewater, which has no estrogen activity, of pH value at 7.45 and the amount of TOC at 20.3 mg dm3, was collected at an effluent of a water treatment facility. A part of the model wastewater was diluted into one-second or one-twenties with pure water (TOC : 4 ppb, electric resistance : 18.2 MO cm1) supplied from Milli-pore Milli-Q system in order to prepare the samples containing different amounts of TOC. 17b-estradiol (GR, Tokyo Chemical Industry) at 1.8 nmol dm3 or p-nonylphenols (mixture of isomers with branched side chains, Tokyo Chemical Industry) at 1 mmol dm3 were added to each wastewater to prepare the model wastewater samples. The g-ray irradiations were carried out at 298 K using 60 Co g-ray sources at JAEA, Takasaki, to the doses in the range of 133–1000 Gy (Gy ¼ J kg1) at dose rates ranging from 5 to 2000 Gy h1. 2.2. Analysis An HPLC (Agilent, 1100 series) with a reverse-phase column (Shodex, RS pak DE-613) was used for analyses of E2 or NP solutions at 313 K before and after g-ray irradiations. Mixture of pure water and methanol (for HPLC Analysis, Wako) were used as an eluent. Mass spectrometer (JEOL, LC-mate) connected with the HPLC was used to determine the concentration of E2 before and after g-ray irradiation. Amounts of the TOC were measured by a TOC analyzer (Shimadzu, TOCVwp). pH value of the wastewater was determined using pH/DO meter (HORIBA, D-25). The real wastewaters after g-ray irradiation prepared at pH value of about 3.5 by adding hydrochloric acid were extracted with solid-phase column (Waters, SepPak plus PS-2). The samples were eluted with acetone (for RP, PCB Anal., Kanto Chemical Co., Inc.). The eluents were evaporated to dryness with a gentle stream of nitrogen, and reconstituted by addition of 3 103 dm3 of borate buffer solution mixed boric acid (GR, Wako) with sodium hydroxide (GR, Kanto Chemical Co., Inc.) of the pH value of 9.0. The solutions were extracted two times with 2 103 dm3 of ethylacetate (for RP, PCB Anal., Kanto Chemical Co., Inc.). The extracted solutions were purged with
ARTICLE IN PRESS A. Kimura et al. / Radiation Physics and Chemistry 76 (2007) 699–706
nitrogen gas, and were added to 6 106 dm3 of dimethylsulfoxide (for Biochem., Wako) and 1.44 104 dm3 of MSD medium. The estrogen activities of the solutions were measured by the yeast twohybrid assay with hERa or mERa. Detailed procedure of the assay was described elsewhere (Shiraishi et al., 2003). The wastewater samples after g-ray irradiation were extracted by dichloromethane (for Dioxin Anal. Wako), and dried until removal of the solvent. Each sample was dissolved into 10% aqueous methanol solution and analyzed by ELISA (E2 ELISA Kit, Japan EnviroChemicals) to estimate E2 equivalent concentration (Goda et al., 2000).
3. Results and discussion 3.1. Decrease in estrogen activity of real wastewater Evaluation of estrogen activity is significant for the treatment of EDCs in wastewater because primary products of the EDCs by irradiation show estrogen activity (Kimura et al., 2004a, 2006). Three samples of the real wastewater before irradiation were analyzed by the yeast two-hybrid assay, ELISA and TOC analysis as shown in Table 1. Subtraction of estrogen activities (hEA) using hERa from estrogen activities (mEA) using mERa gives existence of the artificial EDCs in wastewater. ELISA with E2 antibody which selectively reacts with E2 was used to confirm the value of hEA. The hEA and the E2 equivalent concentration of sample 1 were 0.5 and 0.8 ng dm3, respectively, which are lower than the mEA of 8.3 ng dm3. Little estrogenic compound, therefore, is included in sample 1. The hEA of sample 2 was measured at 0.4 ng dm3 but the E2 equivalent concentration was higher (2.8 ng dm3), considering that the hERa would be affected by antagonists to suppress the cross reaction. The mEA of 3.1 ng dm3 was higher than the hEA, and the estrogen activity of sample 2 comes from the artificial chemicals. Sample 3 has 5.1 ng dm3 of the hEA and 3.3 ng dm3 of the E2 equivalent concentration before irradiation, and the difference between hEA and E2 equivalent
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concentration derives from estrogen activities of estrogenic compounds except E2. The mEA which is considered to be the sum of estrogen activity of the estrogenic compounds and the artificial EDCs was 11.3 ng dm3. Estrogen activity of sample 3 partly comes from the estrogenic compounds. Treatment of the wastewater is required to decrease the estrogen activity to less than 1 ng dm3, which is a lower limit concentration of appearance of endocrine disrupting property. Estrogen activities of the real wastewaters as a function of dose of g-ray irradiation are shown in Fig. 1. The doses for decrease in mEA of sample 1–3 below 1 ng dm3, D1 ng, were estimated at 100, 200 and 150 Gy, respectively. The D1 ng of sample 2 were estimated by an extrapolation of the decomposition curves of mEA. Since the D1 ng of E2 at 1.8 nmol dm3 in pure water is estimated at 5 Gy in a previous work (Kimura et al., 2004a), elimination of estrogen activity of real wastewater is considered to be interfered by organic impurities. Every mEA initially increased and then decreased by the irradiation, indicating that decomposition products in the real wastewaters also have the estrogen activity. The decomposition curves of a trace amount of E2 and NPs in pure water by g-ray irradiation under air saturated conditions are in agreement with that under deoxygenated condition (Kimura et al., 2004a, 2006). Since concentration of the EDCs is very low, a trace amount of dissolved oxygen would enhance the oxidation of EDCs. The decomposition efficiency of EDCs by g-ray irradiation is constant in the range of pH 2–8 (Kimura et al., 2004b), being enough to cover the standard pH values of the rivers in Japan (6.0–8.5). Effects of the pH and oxygen, therefore, would be negligible even with coexisting organics in this study. 3.2. Decomposition of E2 and NPs in model wastewater Decomposition efficiency of EDCs by hydroxyl radicals would be interfered by the organic compounds in wastewater. The EDCs react with hydroxyl radicals within a short time span (Kimura et al., 2004a, 2006): k1
EDCs þ OH ! Product 1a; Product 1b
(1)
Table 1 Estrogen activity, 17b-estradiol equivalent concentration and the amount of total organic carbon in wastewaters Estrogen activity/ng dm3
1 2 3
hEA
mEA
0.5 0.4 5.1
8.3 3.1 11.3
E2 equivalent conc./ng dm3
TOC/mg dm3
0.8 2.8 3.3
7.25 8.66 25.4
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Product 1a has estrogen activity and aromaticity, but Product 1b does not have and is counted in organic compounds:
Estrogen acitivity / ng dm-3
15 mEA hEA
k2
Product 1a þ OH ! Product 2 ðsecondary productÞ. 10
(2) Product 2 is assumed to have no estrogen activity. Organic compounds (OC) having no estrogen activity in wastewater also react with hydroxyl radicals:
5
k3
OC þ OH ! Unknown products:
(3)
These reactions competitively occur and the rate of elimination of [EDCs] is given as follows: 0
0
50
(a)
100
150
Dose / Gy
Estrogen activity / ng dm-3
15 mEA hEA
where D, GOH and Na are absorbed dose of the wastewater, G-value of hydroxyl radical and Avogadro’s number, respectively. The k1, k2 and k3 are considered to be about 107–1010 mol1 dm3 s1, and the concentration of OC is about 107 times higher than that of EDCs and that of Product 1a. Eq. (4) leads to
10
5
0
0
50
(b)
100
150
Dose / Gy 20
Estrogen activity / ng dm-3
mEA hEA
10
0 (c)
0
50
100
d½EDCs GOH ¼ dD 100 1:6 1019 N a k1 ½EDCs , k1 ½EDCs þ k2 ½Product1a þ k3 ½OC ð4Þ
150
Dose / Gy
Fig. 1. Estrogen activities estimated using medaka estrogen receptor (&) and human estrogen receptor (n) for real wastewaters by g-ray irradiation.
d½EDCs G OH k1 ½EDCs ¼ , dD 100 1:6 1019 N a k3 ½OC
A ½EDCs ¼ ½EDCs0 exp D ½OC G OH k1 A¼ . 19 100 1:6 10 N a k3
(5)
ð6Þ
Decomposition efficiency of EDCs was represented as A/[OC]. Because these E2 or NPs are the typical chemicals in estrogenic compounds and artificial EDCs, respectively, the model wastewaters containing these samples were investigated. The amount of TOC is the sum of the concentration of EDCs and the other OC. The concentration of EDCs, however, was about 106 times lower than that of the other OC, the amount of TOC was used as the substitution of [OC] in this research. Decomposition of E2 in the model wastewaters by g-ray irradiation at each TOC concentration is shown in Fig. 2. Although E2 at an initial concentration of 1.8 nmol dm3 in pure water (TOC: 4 106 g dm3) was decomposed at a dose of 10 Gy, the model wastewaters required doses in the range of 50–200 Gy. Each plot was fitted with Eq. (6). The decomposition efficiencies, A/[OC], decreased with the increase in the amount of TOC in the model wastewaters as shown in Fig. 3. The value of A is estimated to be 2.5 104 g dm3 Gy1, and A/[OC] decreases sharply
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[×10-9]
[×10-6] 1
2
20.3×10-3 g dm-3
20.3×10-3 g dm-3 10.2×10-3 g dm-3
10.2×10-3 g dm-3
0.8
1.02×10-3 g dm-3
Concentration / mol dm-3
Concentration / mol dm-3
703
4×10-6 g dm-3 1
1.02×10-3 g dm-3 4×10-6 g dm-3
0.6
0.4
0.2
0
0 0
100 Dose / Gy
200
Fig. 2. Concentration of 17b-estradiol in model wastewater after g-ray irradiation: the amount of total organic carbon in each sample was set by dilution of Mill-Q water at 20.3 103 g dm3 (&), 10.3 103 g dm3 (J), 1.03 103 g dm3 (n) and 4 106 g dm3 (K: Mill-Q water).
200
400 600 Dose / Gy
800
1000
Fig. 4. Concentration of p-nonylphenol in model wastewater as a function of g-ray dose: the amount of total organic carbon in each sample was set at 20.3 103 g dm3 (&), 10.3 103 g dm3 (J), 1.03 103 g dm3 (n) and 4 106 g dm3 (K: Mill-Q water).
be carried out in reactions (1)–(3), and decomposition efficiency decreased with the increasing amount of TOC as the function of the inverse proportion.
0.5
Decomposition efficiency (A/[OC]) / Gy-1
0
0.4
3.3. Simulation of decrease in estrogen activity of real wastewater
0.3
Decrease in estrogen activities of the real wastewaters was simulated with Eqs. (1)–(6). The estrogen activity of the real wastewater, EA, is defined as follows:
0.2
EA ¼ CR1 ½EDC1 þ CR2 ½EDC2 þ þ CRn ½EDCn , (7)
0.1
0
0
10
20
30
Total organic carbon / ×10-3 g dm-3 Fig. 3. Decomposition efficiency (A/[OC]) of 17b-estradiol in model wastewater depending on the amount of total organic carbon.
with the concentration of TOC up to 10 mg dm3 and then slowly decreases. The decomposition of NPs in the model wastewater was also gradual with the increase in the amount of TOC as shown in Fig. 4, and could be fitted with Eq. (6). The value of A is estimated to be 1.0 104 g dm3 Gy1. The decomposition of the EDCs by hydroxyl radicals in model wastewater would
where CR is the cross reactivity of the EDCs with the estrogen receptors. If the primary products have estrogen activity while the secondary ones do not have, the estrogen activity after irradiation will be presented as follows: EA ¼ CR1 ½EDC1 þ CR2 ½Product 1a.
(8)
Formation of Product 1a is assumed to be equal with that of Product 1b. Formation and decomposition of Product 1a is represented by Eq. (5) as follows: d½Product 1a A A k2 ½Product 1a. ¼ ½EDCs1 dD ½OC ½OC k1 (9) Dose dependences of hEA and mEA of the real wastewater are calculated with Eqs. (6), (8) and (9) by FACSIMILE for Windows (version 2.0104, AEA Technology plc) as shown in Fig. 5. The k1 is set at
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products would be less than that of E2, which shows one of the highest estrogen activity in the chemicals. The values of A are used at 1.0 104 and 2.5 104 g dm3 Gy1 obtained by the decomposition of NPs and E2 in the model wastewater. Samples 1 and 2 have low concentration of TOC and simulation curves of mEA for these samples have shoulder. While the estrogen activity of sample 3 which have high TOC concentration decrease exponentially. Each hEA of samples describes the exponential function and the irradiation products from EDCs in wastewater contribute little increment in hEA. The amounts of TOC are significant for treatment of EDCs in wastewater by advanced oxidation technologies.
Estrogen acitivity / ng dm-3
15 Sample 1 Sample 2 Sample 3 10
5
0
0
50
(a)
100
150
6 Sample 1 Sample 2 Sample 3
Estrogen acitivity / ng dm-3
5
4
3
2
1
0 (b)
3.4. Economical evaluation
Dose / Gy
0
50
100
150
Dose / Gy
Fig. 5. Simulation of decrease in estrogen activity using medaka estrogen receptor (a) and human estrogen receptor (b).
1.6 1010 mol1 dm3 s1, which is the rate constant of E2 or NPs with hydroxyl radicals evaluated by the competition reaction method with phenol in a previous work (Kimura et al., 2004a). This value is the diffusioncontrolled limit of aromatic compounds with hydroxyl radicals (Ashton et al., 1995; Roder et al., 1999). We consider that Product 1a has the same rate constant, because Savel’eva et al. (1972) suggest that the rate constant of aromatic compounds with hydroxyl radicals increases with OH-addition. The CR1 and CR2 for mEA are determined to be 1.0 104 and 2.0 104 being constituent with the fact that the irradiation products from NPs would have higher estrogen activity than the NPs (Kimura et al., 2006). The CR1 and CR2 for hEA is set at 1 and 0.1 since estrogen activity of the irradiation
Application of radiation to the treatment of EDCs in secondary effluent from sewage treatment plant is discussed on the basis of the results of the decomposition of EDCs in wastewater by g-ray irradiation. The irradiation system is assumed to be the electron beam accelerator which is easy to newly establishment and to attach to the existent wastewater treatment facilities. Electron beam is used to decrease chemical oxygen demand (COD) in the secondary effluent from the sewage treatment plant (JAERI, 1995). Electron beam accelerator (5 MeV, total beam power 300 kW) has been applied for the commercial plant of wastewater from a papermill (Shin et al., 2002). Economical cost for decomposition of EDCs in wastewater by electron beam is evaluated on the basis of these pilot plant experiments. Consistency of dose evaluation by g-ray and electron beam has been confirmed by Kojima et al (2000), and the replacement of g-ray to electron beam is suitable for the pilot plant experiment. Elimination of the estrogen activity of wastewater by electron beam is sufficiently accomplished at a dose of about 200 Gy. The treatment plant of electron beam for the recirculation of 10,000 m3 day1 requires electron beam accelerator at a total power of 280 kW (5 MeV, 56 mA) (JAERI, 1995). The irradiation is carried out under continuous flow condition, and the wastewater is supplied with the jet nozzle as a thin layer. The initial investment is set at about 600 million yen (15 yen m3), which is the sum of the cost of the electron beam accelerator having the endurance life of 15 years and the personnel costs. The consumption of the electric power for an operation of the electron beam accelerator is estimated to be 2 yen m3, and the total running cost for the plant is estimated to be 17 yen m3 in Japan. For example, the charges of the treatment plants in Gunma, Japan were set in the range of 30–140 yen m3, the electron beam treatment system is considered to have the potentiality of the attachment to the treatment plants.
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4. Conclusion Ionizing radiation was tested for the treatment of wastewater having estrogen activities, which were estimated by the yeast two-hybrid assay using human or medaka estrogen receptors. The estrogen activity derived from the estrogenic compounds in the real wastewater decreased with dose. On the other hands, estrogen activity of the real wastewaters containing artificial endocrine disrupting chemicals (EDCs) increased initially and then decreased. The D1 ng of the wastewater was estimated to be about 200 Gy. The result of the decomposition of E2 or NPs in model wastewater suggests that the D1 ng is determined by the amounts of TOC in the wastewater. The economic cost of the treatment plant of EDCs using electron beam was estimated to be 17 yen m3. Ionizing radiation should contribute for the wastewater treatment as the advanced oxidation technology in the near future.
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Radiation Physics and Chemistry 76 (2007) 699–706 www.elsevier.com/locate/radphyschem
Treatment of wastewater having estrogen activity by ionizing radiation Atsushi Kimuraa,c,, Mitsumasa Taguchia,c, Yoshimi Ohtanib, Yoshitaka Shimadab, Hiroshi Hiratsukac, Takuji Kojimaa,c a Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki-shi, Gunma 370-1292, Japan Gunma Prefectual Institute of Public Health and Environmental Sciences, 378 Kamioki-machi, Maebashi-shi, Gunma 371-0052, Japan c Gunma University, 1-5-1 Tenjin-cho, Kiryu-shi, Gunma 376-8515, Japan
b
Received 21 March 2006; accepted 7 April 2006
Abstract Decomposition of endocrine disrupting chemicals (EDCs) in wastewater was investigated by use of 60Co g-ray. Estrogen activities of wastewaters were estimated by the yeast two-hybrid assay based on human or medaka estrogen receptors. The dose required for the elimination of estrogen activity of wastewater below 1 ng dm3 was about 200 Gy (J kg1). The elimination dose of the estrogen activity depended on the amounts of total organic carbons in wastewater. The economic cost of the treatment process of EDCs using electron beam was estimated at 17 yen m3. r 2006 Elsevier Ltd. All rights reserved. Keywords: Endocrine disrupting chemicals; Wastewater;
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Co g-rays; Yeast two-hybrid assay; Total organic carbon; Economic cost
1. Introduction Environmental pollution by toxic and persistent organic chemicals is widely spread. Some of such chemicals that mimic a natural hormone or disrupt endocrine system in livings to give ill effects are so-called endocrine disrupting chemicals (EDCs) (Colborn et al., 1996). The endocrine disrupting properties of the EDCs were investigated by the cell proliferation bioassay in the 1990s (Soto et al., 1991; Sumpter and Jobling, 1995). Monitoring and screening tests of EDCs have been carried out from the latter half of the 1990s in Japan (Ministry of the Environment, Japan, 1998). Corresponding author. Japan Atomic Energy Agency, 1233 Watanuki-machi, Takasaki-shi, Gunma 370-1292, Japan. E-mail address: [email protected] (A. Kimura).
17b-estradiol (E2: 1,3,5(10)-estratriene-3,17b-diol) is a natural chemical having the highest estrogen activity in water-environment and draws much attention as one of the EDCs (Routledge and Sumpter, 1996, 1997; Routledge et al., 1998; Sumpter and Jobling, 1995). p-Nonylphenols (NPs), 2,2-bis-(4-hydroxyphenyl)-propane and tert-octylphenol were definitely recognized as EDCs (Ministry of the Environment, Japan, 2001). Treatment of EDCs already released into waterenvironment has been attempted by the activated sludge system, and a result of this system is found to be insufficient to eliminate them. Advanced oxidation technologies such as ozolysis, ozone–UV system, ozone–hydrogen peroxide system, photocatalytic processes and radiolysis have been actively studied to achieve complete elimination of persistent organic
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compounds (Boye et al., 2002; Getoff, 1996, 2002; He et al., 2002; Jun et al., 2006; Ku et al., 1997; Liu et al., 2004; Mezyk et al., 2004; Nakashima et al., 2002; Ohko et al., 2001; Winarno and Getoff, 2002). However, the commercial plant based on these methods was not applied since the reactions of oxidation species with the EDCs have not been clearly understood for real-scale treatment. In the series of our research work, hydroxyl radicals generated in water by 60Co g-rays are useful for the decomposition of trace amounts of EDCs (Kimura et al., 2004a, b, 2006). The E2 concentration initially at 1.8 nmol dm3 in water decreases lower than the detection level of LC-MS (o 0.1 nmol dm3) at a dose of 10 Gy but ‘‘the estrogen activity’’ of the E2 solution is not eliminated up to 50 Gy, in other words the decomposition products from E2 have also ‘‘the estrogen activity’’. ‘‘The estrogen activity’’ of chemicals is the cross reactivity of chemicals with the estrogen receptor, and E2 is used as a standard samples of the bioassay because of its 100% cross reactivity. NPs, which exhibit one of the highest estrogen activity among artificial chemicals, have about 0.1% of the cross reactivity with the estrogen receptor. NPs are also decomposed by radiation-induced hydroxyl radicals to produce two OHadducts ascribed to p-nonylcatechol and 1-(p-hydroxyphenyl)-1-nonanol. We showed that irradiation products also have higher estrogen activity than NPs by use of the yeast two-hybrid assay. Estrogen activities of the NP solution with an initial concentration of 20 mmol dm3 were also eliminated at 5000 Gy. Now, our research is in the stage to examine whether the ionizing radiation is applicable or not to the treatment of the EDCs in wastewater as the advanced oxidation technologies. Treatment of real wastewater having the estrogen activity was studied by use of g-ray irradiation in the present paper. Estrogen activity of the wastewater was analyzed by the yeast two-hybrid assay, which can estimate estrogen activities using human estrogen receptor (hERa) and medaka estrogen receptor (mERa). The hERa has a high reactivity with estrogenic compounds such as estrone, E2 and estriol released by animals. The mERa reacts not only with the estrogenic compounds but also artificial EDCs such as NPs. The elimination rate of the estrogen activity of the wastewater by radiation-induced hydroxyl radicals was lower than that of pure water. E2 and NPs were dissolved into the wastewaters having no estrogen activity, and then used as the model wastewater. The decomposition efficiencies of E2 or NPs were found to depend on the amount of total organic carbon (TOC) in their solutions, which were obtained from the decomposition curves of them in model wastewater by g-ray irradiation. These results enable to estimate doses for essential treatment of EDCs in wastewater.
2. Experimental 2.1. Sample preparation and irradiation Real wastewater samples were obtained from the three different secondary effluents of water treatment plants with the activated sludge system. The amounts of TOC of these samples were 7.25, 8.66 and 25.4 mg dm3, and the pH values were 8.24, 8.28 and 7.49, respectively. Each sample at 0.1 dm3 was used after filtration with a paper (Whatman, Qualitative Circles 150 mm f) to remove dusts. A model wastewater, which has no estrogen activity, of pH value at 7.45 and the amount of TOC at 20.3 mg dm3, was collected at an effluent of a water treatment facility. A part of the model wastewater was diluted into one-second or one-twenties with pure water (TOC : 4 ppb, electric resistance : 18.2 MO cm1) supplied from Milli-pore Milli-Q system in order to prepare the samples containing different amounts of TOC. 17b-estradiol (GR, Tokyo Chemical Industry) at 1.8 nmol dm3 or p-nonylphenols (mixture of isomers with branched side chains, Tokyo Chemical Industry) at 1 mmol dm3 were added to each wastewater to prepare the model wastewater samples. The g-ray irradiations were carried out at 298 K using 60 Co g-ray sources at JAEA, Takasaki, to the doses in the range of 133–1000 Gy (Gy ¼ J kg1) at dose rates ranging from 5 to 2000 Gy h1. 2.2. Analysis An HPLC (Agilent, 1100 series) with a reverse-phase column (Shodex, RS pak DE-613) was used for analyses of E2 or NP solutions at 313 K before and after g-ray irradiations. Mixture of pure water and methanol (for HPLC Analysis, Wako) were used as an eluent. Mass spectrometer (JEOL, LC-mate) connected with the HPLC was used to determine the concentration of E2 before and after g-ray irradiation. Amounts of the TOC were measured by a TOC analyzer (Shimadzu, TOCVwp). pH value of the wastewater was determined using pH/DO meter (HORIBA, D-25). The real wastewaters after g-ray irradiation prepared at pH value of about 3.5 by adding hydrochloric acid were extracted with solid-phase column (Waters, SepPak plus PS-2). The samples were eluted with acetone (for RP, PCB Anal., Kanto Chemical Co., Inc.). The eluents were evaporated to dryness with a gentle stream of nitrogen, and reconstituted by addition of 3 103 dm3 of borate buffer solution mixed boric acid (GR, Wako) with sodium hydroxide (GR, Kanto Chemical Co., Inc.) of the pH value of 9.0. The solutions were extracted two times with 2 103 dm3 of ethylacetate (for RP, PCB Anal., Kanto Chemical Co., Inc.). The extracted solutions were purged with
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nitrogen gas, and were added to 6 106 dm3 of dimethylsulfoxide (for Biochem., Wako) and 1.44 104 dm3 of MSD medium. The estrogen activities of the solutions were measured by the yeast twohybrid assay with hERa or mERa. Detailed procedure of the assay was described elsewhere (Shiraishi et al., 2003). The wastewater samples after g-ray irradiation were extracted by dichloromethane (for Dioxin Anal. Wako), and dried until removal of the solvent. Each sample was dissolved into 10% aqueous methanol solution and analyzed by ELISA (E2 ELISA Kit, Japan EnviroChemicals) to estimate E2 equivalent concentration (Goda et al., 2000).
3. Results and discussion 3.1. Decrease in estrogen activity of real wastewater Evaluation of estrogen activity is significant for the treatment of EDCs in wastewater because primary products of the EDCs by irradiation show estrogen activity (Kimura et al., 2004a, 2006). Three samples of the real wastewater before irradiation were analyzed by the yeast two-hybrid assay, ELISA and TOC analysis as shown in Table 1. Subtraction of estrogen activities (hEA) using hERa from estrogen activities (mEA) using mERa gives existence of the artificial EDCs in wastewater. ELISA with E2 antibody which selectively reacts with E2 was used to confirm the value of hEA. The hEA and the E2 equivalent concentration of sample 1 were 0.5 and 0.8 ng dm3, respectively, which are lower than the mEA of 8.3 ng dm3. Little estrogenic compound, therefore, is included in sample 1. The hEA of sample 2 was measured at 0.4 ng dm3 but the E2 equivalent concentration was higher (2.8 ng dm3), considering that the hERa would be affected by antagonists to suppress the cross reaction. The mEA of 3.1 ng dm3 was higher than the hEA, and the estrogen activity of sample 2 comes from the artificial chemicals. Sample 3 has 5.1 ng dm3 of the hEA and 3.3 ng dm3 of the E2 equivalent concentration before irradiation, and the difference between hEA and E2 equivalent
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concentration derives from estrogen activities of estrogenic compounds except E2. The mEA which is considered to be the sum of estrogen activity of the estrogenic compounds and the artificial EDCs was 11.3 ng dm3. Estrogen activity of sample 3 partly comes from the estrogenic compounds. Treatment of the wastewater is required to decrease the estrogen activity to less than 1 ng dm3, which is a lower limit concentration of appearance of endocrine disrupting property. Estrogen activities of the real wastewaters as a function of dose of g-ray irradiation are shown in Fig. 1. The doses for decrease in mEA of sample 1–3 below 1 ng dm3, D1 ng, were estimated at 100, 200 and 150 Gy, respectively. The D1 ng of sample 2 were estimated by an extrapolation of the decomposition curves of mEA. Since the D1 ng of E2 at 1.8 nmol dm3 in pure water is estimated at 5 Gy in a previous work (Kimura et al., 2004a), elimination of estrogen activity of real wastewater is considered to be interfered by organic impurities. Every mEA initially increased and then decreased by the irradiation, indicating that decomposition products in the real wastewaters also have the estrogen activity. The decomposition curves of a trace amount of E2 and NPs in pure water by g-ray irradiation under air saturated conditions are in agreement with that under deoxygenated condition (Kimura et al., 2004a, 2006). Since concentration of the EDCs is very low, a trace amount of dissolved oxygen would enhance the oxidation of EDCs. The decomposition efficiency of EDCs by g-ray irradiation is constant in the range of pH 2–8 (Kimura et al., 2004b), being enough to cover the standard pH values of the rivers in Japan (6.0–8.5). Effects of the pH and oxygen, therefore, would be negligible even with coexisting organics in this study. 3.2. Decomposition of E2 and NPs in model wastewater Decomposition efficiency of EDCs by hydroxyl radicals would be interfered by the organic compounds in wastewater. The EDCs react with hydroxyl radicals within a short time span (Kimura et al., 2004a, 2006): k1
EDCs þ OH ! Product 1a; Product 1b
(1)
Table 1 Estrogen activity, 17b-estradiol equivalent concentration and the amount of total organic carbon in wastewaters Estrogen activity/ng dm3
1 2 3
hEA
mEA
0.5 0.4 5.1
8.3 3.1 11.3
E2 equivalent conc./ng dm3
TOC/mg dm3
0.8 2.8 3.3
7.25 8.66 25.4
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Product 1a has estrogen activity and aromaticity, but Product 1b does not have and is counted in organic compounds:
Estrogen acitivity / ng dm-3
15 mEA hEA
k2
Product 1a þ OH ! Product 2 ðsecondary productÞ. 10
(2) Product 2 is assumed to have no estrogen activity. Organic compounds (OC) having no estrogen activity in wastewater also react with hydroxyl radicals:
5
k3
OC þ OH ! Unknown products:
(3)
These reactions competitively occur and the rate of elimination of [EDCs] is given as follows: 0
0
50
(a)
100
150
Dose / Gy
Estrogen activity / ng dm-3
15 mEA hEA
where D, GOH and Na are absorbed dose of the wastewater, G-value of hydroxyl radical and Avogadro’s number, respectively. The k1, k2 and k3 are considered to be about 107–1010 mol1 dm3 s1, and the concentration of OC is about 107 times higher than that of EDCs and that of Product 1a. Eq. (4) leads to
10
5
0
0
50
(b)
100
150
Dose / Gy 20
Estrogen activity / ng dm-3
mEA hEA
10
0 (c)
0
50
100
d½EDCs GOH ¼ dD 100 1:6 1019 N a k1 ½EDCs , k1 ½EDCs þ k2 ½Product1a þ k3 ½OC ð4Þ
150
Dose / Gy
Fig. 1. Estrogen activities estimated using medaka estrogen receptor (&) and human estrogen receptor (n) for real wastewaters by g-ray irradiation.
d½EDCs G OH k1 ½EDCs ¼ , dD 100 1:6 1019 N a k3 ½OC
A ½EDCs ¼ ½EDCs0 exp D ½OC G OH k1 A¼ . 19 100 1:6 10 N a k3
(5)
ð6Þ
Decomposition efficiency of EDCs was represented as A/[OC]. Because these E2 or NPs are the typical chemicals in estrogenic compounds and artificial EDCs, respectively, the model wastewaters containing these samples were investigated. The amount of TOC is the sum of the concentration of EDCs and the other OC. The concentration of EDCs, however, was about 106 times lower than that of the other OC, the amount of TOC was used as the substitution of [OC] in this research. Decomposition of E2 in the model wastewaters by g-ray irradiation at each TOC concentration is shown in Fig. 2. Although E2 at an initial concentration of 1.8 nmol dm3 in pure water (TOC: 4 106 g dm3) was decomposed at a dose of 10 Gy, the model wastewaters required doses in the range of 50–200 Gy. Each plot was fitted with Eq. (6). The decomposition efficiencies, A/[OC], decreased with the increase in the amount of TOC in the model wastewaters as shown in Fig. 3. The value of A is estimated to be 2.5 104 g dm3 Gy1, and A/[OC] decreases sharply
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[×10-9]
[×10-6] 1
2
20.3×10-3 g dm-3
20.3×10-3 g dm-3 10.2×10-3 g dm-3
10.2×10-3 g dm-3
0.8
1.02×10-3 g dm-3
Concentration / mol dm-3
Concentration / mol dm-3
703
4×10-6 g dm-3 1
1.02×10-3 g dm-3 4×10-6 g dm-3
0.6
0.4
0.2
0
0 0
100 Dose / Gy
200
Fig. 2. Concentration of 17b-estradiol in model wastewater after g-ray irradiation: the amount of total organic carbon in each sample was set by dilution of Mill-Q water at 20.3 103 g dm3 (&), 10.3 103 g dm3 (J), 1.03 103 g dm3 (n) and 4 106 g dm3 (K: Mill-Q water).
200
400 600 Dose / Gy
800
1000
Fig. 4. Concentration of p-nonylphenol in model wastewater as a function of g-ray dose: the amount of total organic carbon in each sample was set at 20.3 103 g dm3 (&), 10.3 103 g dm3 (J), 1.03 103 g dm3 (n) and 4 106 g dm3 (K: Mill-Q water).
be carried out in reactions (1)–(3), and decomposition efficiency decreased with the increasing amount of TOC as the function of the inverse proportion.
0.5
Decomposition efficiency (A/[OC]) / Gy-1
0
0.4
3.3. Simulation of decrease in estrogen activity of real wastewater
0.3
Decrease in estrogen activities of the real wastewaters was simulated with Eqs. (1)–(6). The estrogen activity of the real wastewater, EA, is defined as follows:
0.2
EA ¼ CR1 ½EDC1 þ CR2 ½EDC2 þ þ CRn ½EDCn , (7)
0.1
0
0
10
20
30
Total organic carbon / ×10-3 g dm-3 Fig. 3. Decomposition efficiency (A/[OC]) of 17b-estradiol in model wastewater depending on the amount of total organic carbon.
with the concentration of TOC up to 10 mg dm3 and then slowly decreases. The decomposition of NPs in the model wastewater was also gradual with the increase in the amount of TOC as shown in Fig. 4, and could be fitted with Eq. (6). The value of A is estimated to be 1.0 104 g dm3 Gy1. The decomposition of the EDCs by hydroxyl radicals in model wastewater would
where CR is the cross reactivity of the EDCs with the estrogen receptors. If the primary products have estrogen activity while the secondary ones do not have, the estrogen activity after irradiation will be presented as follows: EA ¼ CR1 ½EDC1 þ CR2 ½Product 1a.
(8)
Formation of Product 1a is assumed to be equal with that of Product 1b. Formation and decomposition of Product 1a is represented by Eq. (5) as follows: d½Product 1a A A k2 ½Product 1a. ¼ ½EDCs1 dD ½OC ½OC k1 (9) Dose dependences of hEA and mEA of the real wastewater are calculated with Eqs. (6), (8) and (9) by FACSIMILE for Windows (version 2.0104, AEA Technology plc) as shown in Fig. 5. The k1 is set at
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products would be less than that of E2, which shows one of the highest estrogen activity in the chemicals. The values of A are used at 1.0 104 and 2.5 104 g dm3 Gy1 obtained by the decomposition of NPs and E2 in the model wastewater. Samples 1 and 2 have low concentration of TOC and simulation curves of mEA for these samples have shoulder. While the estrogen activity of sample 3 which have high TOC concentration decrease exponentially. Each hEA of samples describes the exponential function and the irradiation products from EDCs in wastewater contribute little increment in hEA. The amounts of TOC are significant for treatment of EDCs in wastewater by advanced oxidation technologies.
Estrogen acitivity / ng dm-3
15 Sample 1 Sample 2 Sample 3 10
5
0
0
50
(a)
100
150
6 Sample 1 Sample 2 Sample 3
Estrogen acitivity / ng dm-3
5
4
3
2
1
0 (b)
3.4. Economical evaluation
Dose / Gy
0
50
100
150
Dose / Gy
Fig. 5. Simulation of decrease in estrogen activity using medaka estrogen receptor (a) and human estrogen receptor (b).
1.6 1010 mol1 dm3 s1, which is the rate constant of E2 or NPs with hydroxyl radicals evaluated by the competition reaction method with phenol in a previous work (Kimura et al., 2004a). This value is the diffusioncontrolled limit of aromatic compounds with hydroxyl radicals (Ashton et al., 1995; Roder et al., 1999). We consider that Product 1a has the same rate constant, because Savel’eva et al. (1972) suggest that the rate constant of aromatic compounds with hydroxyl radicals increases with OH-addition. The CR1 and CR2 for mEA are determined to be 1.0 104 and 2.0 104 being constituent with the fact that the irradiation products from NPs would have higher estrogen activity than the NPs (Kimura et al., 2006). The CR1 and CR2 for hEA is set at 1 and 0.1 since estrogen activity of the irradiation
Application of radiation to the treatment of EDCs in secondary effluent from sewage treatment plant is discussed on the basis of the results of the decomposition of EDCs in wastewater by g-ray irradiation. The irradiation system is assumed to be the electron beam accelerator which is easy to newly establishment and to attach to the existent wastewater treatment facilities. Electron beam is used to decrease chemical oxygen demand (COD) in the secondary effluent from the sewage treatment plant (JAERI, 1995). Electron beam accelerator (5 MeV, total beam power 300 kW) has been applied for the commercial plant of wastewater from a papermill (Shin et al., 2002). Economical cost for decomposition of EDCs in wastewater by electron beam is evaluated on the basis of these pilot plant experiments. Consistency of dose evaluation by g-ray and electron beam has been confirmed by Kojima et al (2000), and the replacement of g-ray to electron beam is suitable for the pilot plant experiment. Elimination of the estrogen activity of wastewater by electron beam is sufficiently accomplished at a dose of about 200 Gy. The treatment plant of electron beam for the recirculation of 10,000 m3 day1 requires electron beam accelerator at a total power of 280 kW (5 MeV, 56 mA) (JAERI, 1995). The irradiation is carried out under continuous flow condition, and the wastewater is supplied with the jet nozzle as a thin layer. The initial investment is set at about 600 million yen (15 yen m3), which is the sum of the cost of the electron beam accelerator having the endurance life of 15 years and the personnel costs. The consumption of the electric power for an operation of the electron beam accelerator is estimated to be 2 yen m3, and the total running cost for the plant is estimated to be 17 yen m3 in Japan. For example, the charges of the treatment plants in Gunma, Japan were set in the range of 30–140 yen m3, the electron beam treatment system is considered to have the potentiality of the attachment to the treatment plants.
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4. Conclusion Ionizing radiation was tested for the treatment of wastewater having estrogen activities, which were estimated by the yeast two-hybrid assay using human or medaka estrogen receptors. The estrogen activity derived from the estrogenic compounds in the real wastewater decreased with dose. On the other hands, estrogen activity of the real wastewaters containing artificial endocrine disrupting chemicals (EDCs) increased initially and then decreased. The D1 ng of the wastewater was estimated to be about 200 Gy. The result of the decomposition of E2 or NPs in model wastewater suggests that the D1 ng is determined by the amounts of TOC in the wastewater. The economic cost of the treatment plant of EDCs using electron beam was estimated to be 17 yen m3. Ionizing radiation should contribute for the wastewater treatment as the advanced oxidation technology in the near future.
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