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Removal of steroid estrogens from waste activated sludge using Fentonoxidation: Influencing factors and degradation intermediates

Yongmei Li ⇑, Ai ZhangState Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China

h i g h l i g h t s

� Fenton oxidation is effective in removing estrogens from waste activated sludge.� The proper reaction conditions are recommended for both estrogen removal and sludge solubilization.� Hydroxyl radical takes the most important role in Fenton oxidation of estrogens in sludge.� Pregn-4-ene-3,20-dione and pregn-4-en-20-yn-3-one are first observed as intermediates of estrogens.

a r t i c l e i n f o

Article history:Received 31 January 2013Received in revised form 12 October 2013Accepted 14 October 2013Available online 9 November 2013

Keywords:Endocrine disrupting compoundsFenton oxidationWaste activated sludgeReaction conditionDegradation intermediate

a b s t r a c t

The presence of endocrine disrupting compounds (EDCs) in waste activated sludge (WAS) is raising con-cerns about their influence on animals and the overall food cycle. Traditional sludge stabilization pro-cesses cannot remove EDCs effectively. The main objective of this work was to study the removal offour estrogens (estrone (E1), 17b-estradiol (E2), estriol (E3), and 17a-ethinylestradiol (EE2)) in wasteactivated sludge treated with Fenton oxidation. The effects of H2O2 dosage, initial pH, reaction time,and Fe(II) to H2O2 molar ratio were investigated. Base on both the removal of estrogens and the solubi-lization of WAS, the proper reaction conditions were recommended as follows: H2O2 dos-age = 15.62 mmol g�1, initial pH = 3, reaction time = 60 min, Fe(II) to H2O2 molar ratio = 0.167. Underthese conditions, the removal efficiencies of E1, E2, EE2, and E3 were 70%, 90%, 84% and 98%, respectively;compared with non-Fenton treatment, a 24-fold increase in STOC was achieved, and the extent of solu-bilization of TSS and VSS was close to 13 and 20%, respectively. The degradation intermediates weredetected using GC/MS. Results showed that the phenol structures of targets were mostly oxidized tocyclohexenone moieties and quinone-like structures, which indicated that estrogenic activity was weak-ened. Pregn-4-ene-3,20-dione and pregn-4-en-20-yn-3-one were observed for the first time. Fenton oxi-dation was shown to offer a promising alternative method of removing EDCs from sludge in pretreatmentapplications.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Endocrine disrupting compounds (EDCs) are chemicals thathave negative effects on the endocrine systems of humans andwildlife. These include natural estrogens, natural androgens, artifi-cial synthetic estrogens, phytoestrogens, and other industrial com-pounds (Liu et al., 2009). Among steroid estrogens, estrone (E1),17b-estradiol (E2), estriol (E3), and 17a-ethinylestradiol (EE2) arereported to be highly disruptive to the endocrine system (Terneset al., 1999).

During wastewater treatment, some estrogens present in sew-age may be transferred to activated sludge in biological treatmentsystems due to their hydrophobic properties (Li et al., 2011).

Ternes et al. (2002) reported that in activated and digested sludge,concentrations of E1, E2, and EE2 were in the ranges of <2–37, 5–49 and <2–17 ng g�1, respectively. Nieto et al. (2008) indicated thatestrogen concentrations in sludge exceeded 50–100 ng g�1 for E1and 272–406 ng g�1 for E3. These concentrations are high enoughto pose risks to the environment and human health (Mulleret al., 2010). The presence of EDCs in sludge raises concerns regard-ing the use of sludge as fertilizer in agriculture (Kinney et al.,2006). Reducing the impact of EDCs in sludge systems is of consid-erable environmental relevance.

So far, the fate of estrogens during sludge stabilization processis poorly documented (Hamid and Eskicioglu, 2012). Little workhas been done on degradation of E1, E2, EE2, and E3 in sludge treat-ment units despite the fact that these estrogens have been found toexert the majority of estrogenic activity (Nelson et al., 2007). Pre-viously published articles show that effective removal of estrogens

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⇑ Corresponding author. Tel.: +86 21 65982692; fax: +86 21 65986313.E-mail address: liyongmei@tongji.edu.cn (Y. Li).

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is not achieved during traditional sludge stabilization processes.Andersen et al. (2003) measured E1, E2 and EE2 in a wastewatertreatment plant (WWTP) and found a notable increase in the con-centration of E1 and E2 during sludge stabilization. Czajka and Lon-dry (2006) monitored the concentration of EE2 over a 271-d periodin a municipal WWTP anaerobic digester and suggested that EE2degradation was minimal even though electron acceptors had beenreduced and methanogenesis occurred. Muller et al. (2010) con-firmed that full-scale anaerobic digestion did not remove estrogensfrom sludge efficiently. They further indicated that final sludge sta-bilization and dewatering using a thermal-pressurized treatmenttended to increase the estrogen content from anaerobically di-gested sludge to dewatered sludge. This shows that alternativemethods are needed to remove the estrogens from sludge priorto their release into receiving media.

Advanced oxidation processes (AOPs) have drawn particularattention for degradation of emerging micropollutants like EDCs,pharmaceuticals, and personal care products in various aqueousmatrices (Klavarioti et al., 2009). However, only a few investiga-tions into the ability of AOPs to remove EDCs from sludge havebeen conducted (Hamid and Eskicioglu, 2012). Bernal-Martinezet al. (2007) used O3 to pretreat sludge for the removal of polycy-clic aromatic hydrocarbon (PAH) and noted an increase in biode-gradability of PAH. Carballa et al. (2007) studied the effect of O3

on the removal of E1, E2, and EE2 from sludge and noted high re-moval efficiencies for natural estrogens. Qiang et al. (2013) studiedthe degradation of EDCs for O3-treated activated sludge and indi-cated that the EDCs present in activated sludge were effectivelyremoved.

The Fenton process has been used for organic compound oxida-tion due to its highly efficient generation of �OH, as shown in Eq.(1):

Fe2þ þH2O2 ! Fe3þ þ �OHþ OH� ð1Þ

This is an attractive oxidation system because iron is an abun-dant, non-toxic element and H2O2 is environmentally safe (Frontis-tis et al., 2011). The Fenton process can also be used in sludgepretreatment because it can disintegrate extracellular polymersubstances and rupture cell walls, releasing intracellular material.Fenton oxidation can transform refractory organic compounds intoreadily available and soluble compounds, which ultimately in-creases the generation of biogas (Tyagi and Lo, 2011). Dewil et al.(2007) investigated biogas production of sludge with Fenton per-oxidation during anaerobic digestion and showed a 75% increaseover non-Fenton treatments. To date, no studies on the removalof steroid estrogens from sludge with Fenton oxidation have beenconducted.

This research investigated Fenton oxidation of E1, E2, EE2 andE3 in waste activated sludge (WAS). Its purpose was to produceand confirm a useful technology suitable for pretreatment ofsludge containing estrogens. The bulk of the present work is con-cerned with (i) the effects of Fenton oxidation conditions on re-moval of estrogens in WAS and solubilization of WAS; (ii)degradation intermediates of tested estrogens identified by GC/MS to predict their degradation mechanisms and the changes inestrogenicity.

2. Materials and methods

2.1. Chemicals

Estrogens and all organic solvents of HPLC grade were pur-chased from Sigma–Aldrich (USA). Stock estrogen solutions(200 mg L�1) were prepared by dissolving relevant amount of

estrogen in methanol and stored at 4 �C. They were spiked intothe sludge to produce the desired estrogen concentrations.

2.2. Was

The sludge was collected from a sludge thickener in a WWTP inShanghai, China. The main characteristics (average data plus stan-dard deviations of triplicates) were as follows: pH 6.2–6.8, totalsolids (TS) 28.5 ± 1.0 g L�1, volatile solids (VS) 22.3 ± 0.2 g L�1, totalsuspended solids (TSS) 26.8 ± 1.5 g L�1, volatile suspended solids(VSS) 21.2 ± 0.3 g L�1, soluble chemical oxygen demand (SCOD)471 ± 86 mg L�1, and total chemical oxygen demand (TCOD)29.4 ± 5.9 g L�1.

2.3. Fenton oxidation experiments

Fenton oxidation experiments were carried out in 500 mL offlasks stirred with magnetic stirrers at room temperature. 300 mLof sludge containing 1 mg L�1 of estrogens was transferred to theflask. The initial pH was adjusted by NaOH and HCl as appropriate.Specific amounts of ferrous sulfate (0.5 M) and H2O2 (30% v/v) wereimmediately added. The reaction was allowed to proceed for a spe-cific length of time. Then 2 M NaOH was injected into the flask toincrease the pH to 10 to terminate the reaction. Then the sludgewas taken for analysis. Fresh H2O2 and FeSO4 solutions wereprepared daily.

Experiments evaluating the effects of H2O2 dosage, initial pH,reaction time, and Fe(II) to H2O2 molar ratio were conducted bychanging one factor while keeping the others constant. Exceptwhere otherwise stated, the pH was around 3; the H2O2 dosagewas 15.62 mmol g�1; the Fe(II) to H2O2 molar ratio was 0.1, andthe reaction time was 60 min. 6 pHs (1.6–6.8) were tested; theH2O2 dosage ranged from 1.56 to 46.86 mmol g�1; Fe(II) to H2O2

molar ratios of 0.0667–0.25 were tested. Reaction times were setfrom 15 to 120 min. In order to verify the role of �OH radicals,tert-butyl alcohol (t-BuOH, a �OH scavenger) was added at a H2O2

dosage of 6.25 mmol g�1, pH 3, reaction time of 60 min, and Fe(II)to H2O2 molar ratio of 0.146.

2.4. Analytical methods

2.4.1. Estrogen analysisThe sample preparation procedure followed the method of

sludge samples described by Zeng et al. (2009). An HPLC equippedwith a reversed-phase C-18 column (4.6 mm � 250 mm, 5 lm, Agi-lent, USA) was used to analyze samples. The injection volume was50 lL and the flow rate was 1 mL min�1. The separation was per-formed under gradient elution conditions using (A) acetonitrileand (B) water. The solvent program used for E2, EE2, and E3 wasas follows: initial conditions 70% B linearly reduced to 30% B over12 min, then linearly decreased to 0% B over 0.3 min, and then keptisocratic for 10 min. An excitation wavelength of 228 nm and emis-sion wavelength of 316 nm were used for fluorescence detection ofE2, EE2, and E3. For E1, a wavelength of 200 nm was used for UVdetection at a temperature of 40 �C. The solvent program usedfor E1 was kept initial conditions of 50% B for 15 min. Under theseexperimental conditions, the quantification limits of target com-pounds were 62.5 ng g�1. The recoveries were in ranges of 85–92%, 90–101%, 83–94% and 83–93% for E1, E2, EE2 and E3,respectively.

2.4.2. Other analysisTSS and VSS were analyzed before the termination of reactions

according to Standard Methods (APHA, 1999). STOC (soluble totalorganic carbon) was measured using a TOC-VCPN analyzer (Shima-dzu, Japan). TSS0, VSS0, and STOC0 referred to as the parameters of

Y. Li, A. Zhang / Chemosphere 105 (2014) 24–30 25

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WAS before Fenton oxidation. The extent of solubilized TSS andVSS were calculated as follows:

STSS ¼TSS0 � TSS

TSS0� 100% ð2Þ

SVSS ¼VSS0 � VSS

VSS0� 100% ð3Þ

2.5. Identification of degradation intermediates

Identification of intermediates of estrogens during Fenton oxida-tion was achieved using a GC/MS system (ThermoFocus DSQ, USA)equipped with a VF-5MS column (30 m � 0.25 mm � 0.25 lm).

After oxidization for 30 min, 60 mL of sludge sample was takenand freeze-dried. The dried pellets were dissolved in 200 mL ofmethanol and then ultrasonically extracted for 60 min. The samplewas then separated by centrifugation at 8000 rpm for 10 min. Thesupernatant was finally concentrated to 1 mL using rotary evapo-ration equipment in a water bath at 38–39 �C and then used foranalysis.

1 lL of the sample was injected into GC at 200 �C in splitlessmode. The column temperature was controlled at 60 �C for 2 min,heated to 300 �C in 30 �C min�1 increments, and kept at this tem-perature for 8 min. Helium was used as the carrier gas. Tempera-ture for MS ion source was 250 �C and electron energy was70 eV. The MS was operated in total ion chromatogram mode forqualitative analysis from m/z 50 to 600. Blank experiments withouttarget estrogens were conducted to exclude the disturbance of ma-trix of sludge.

3. Results and discussion

3.1. Factors affecting the removal of estrogens and solubilization ofWAS

3.1.1. Effect of H2O2 dosageThe effect of H2O2 dosage on the removal of target estrogens is

shown in Fig. 1a. The removal efficiencies of target estrogens in-creased when H2O2 dosage increased from 1.56 to 31.24 mmol g�1.They were 77%, 94%, 88% and 95% for E1, E2, EE2 and E3, respec-tively, at H2O2 dosage of 31.24 mmol g�1. As the H2O2 dosage fur-ther increased to 46.86 mmol g�1, however, the removalefficiencies decreased to 64%, 81%, 67% and 87% for E1, E2, EE2and E3, respectively.

The reacting system of Fenton oxidation applicable in this studyis summarized in Fig. S1. As shown in Eq. (1), more �OH radicalswere produced at increased dosages of H2O2, resulting in higher re-moval of tested estrogens. However, due to the self-decompositionof H2O2 shown in Eq. (4), extremely high dosages of H2O2 did notimprove removal efficiency (Bouasla et al., 2010).

2H2O2 ! O2 þ 2H2O ð4Þ

Excess H2O2 can also react with Fe3+ forming weaker HO2�

radicals and trapping �OH radicals, as shown in Eqs. (5) and (6)(Mendez-Arriaga et al., 2010).

Fe3þ þH2O2 ! Fe2þ þHO�2 þHþ ð5Þ

H2O2 þ �OH! HO�2 þH2O ð6Þ

Solubilization of WAS during Fenton oxidation was evaluatedbased on the changes of the sludge characteristics such as TSS,VSS and STOC. As shown in Fig. 2a, with the increase of H2O2

dosage, the STSS and SVSS increased and STOC decreased. The STSS

and SVSS at H2O2 dosage of 15.62 mmol g�1 were 10.7% and13.3%, respectively (Fig. 2a). The formation of �OH can rupture cellwalls and release intracellular material, causing the decrease of TSSand VSS (Mohapatra et al., 2011). The STOC observed during Fentonoxidation at H2O2 dosage of 1.56 mmol g�1 was 30.3 times greaterthan STOC0, while at H2O2 dosage of 15.62 mmol g�1, this numberwas decreased to 17.1 times (Fig. 2a). With the improvement of thesludge’s solubilization during Fenton oxidation, organic substanceswere transferred from the solid to the aqueous phase, resulting inan increase in soluble protein and soluble carbohydrate concentra-tions in the aqueous phase (Mohapatra et al., 2010). However, thecontinuous oxidation with excess oxidant may also make the re-leased organic material mineralized, resulting in the decrease ofSTOC. Torres et al. (2007) also observed that 75% of COD and 20%of TOC were removed using the Fenton oxidation for sludge pre-treatment after 180 min.

Taking the estrogen removal and sludge solubilization as wellas sludge treatment cost into consideration, the H2O2 dosage of15.62 mmol g�1 is recommended for the pre-treatment of sludgeusing Fenton oxidation.

3.1.2. Effect of initial pHThe effect of initial pH on the removal of tested estrogens is

illustrated in Fig. 1b. The removal efficiencies of target compoundsdecreased with the increase of pH, because pH can influence thegeneration of �OH radical. The removal efficiencies of EDCs in-creased notably with the decrease of pH from 6.8 to 3.1, but some-what slowed down when the pH value decreased below 3.1(Fig. 1b). For example, when pH decreased from 6.8 to 3.1, the re-moval efficiencies of E1, E2, EE2 and E3 increased from 45%, 69%,50% and 92% to 54%, 78%, 65% and 95%, respectively; when pH fur-ther decreased to 1.6, the removal efficiencies of E1, E2, EE2 and E3only increased to 56%, 78%, 68% and 97%, respectively (Fig. 1b). Therise of pH can cause the formation of an inactive hydroperoxide an-ion due to H2O2 dissociation (Fig. S1). The HO�2 acts as an efficientscavenger of �OH radicals as presented in Eq. (7), which leads toinhibition of degradation (Bouasla et al., 2010).

HO�2 þ �OH! H2Oþ O��2 ð7Þ

When pH was greater than 4, the concentration of free iron spe-cies decreased due to formation of complexes that could not reactwith H2O2 easily (Neyens and Baeyens, 2003). H2O2 became unsta-ble and decomposed to oxygen when pH was high. It also lost itsoxidation ability, as presented in Eq. (4).

The decrease in pH caused the increase of STSS, SVSS, and STOC(Fig. 2b). When pH decreased from 6.8 to 2.5, the STSS, SVSS, andSTOC/STOC0 increased slightly. However, when pH further de-creased from 2.5 to 1.6, STSS and STOC increased notably (Fig. 2b).Extreme acidic conditions may lead to serious lysis or disintegra-tion of sludge cells, and thus cause the significant decrease ofTSS and increase of STOC. Furthermore, such low pH does not facil-itate the subsequent sludge treatment. Therefore, considering bothestrogen removal and sludge solubilization, the proper pH valueshould be set around 3.

3.1.3. Effect of reaction timeThe removal of target estrogens increased at longer reaction

times (Fig. 1c). The degradation of target estrogens was fast duringthe first 15 min but did not vary significantly at reaction timesexceeding 60 min.

Reaction time was mainly influenced by the rate of formation of�OH and its reaction rate with organics. At the beginning of thereaction, the concentration of �OH was high, which allowed

26 Y. Li, A. Zhang / Chemosphere 105 (2014) 24–30

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considerable contact with target estrogens. As �OH was consumed,the degradation rates began to slow down.

The sludge solubilization also increased with the increase ofreaction time (Fig. 2c), indicating the organic part of the solidswas released continuously into the water phase during Fenton oxi-dation. When the reaction time increased from 15 to 60 min, thesolubilization rate increased slightly. However, when the reactiontime further increased from 60 to 120 min, the VSS solubilizationrate and STOC increased significantly (Fig. 2c). This means reactiontime of >60 min is needed for effective solubilization of WAS.

The extension of reaction time may increase the expenditure ofconstruction, taking both the removal of EDCs and sludge treat-ment cost into consideration, the reaction time of 60–90 min isrecommended.

3.1.4. Effect of Fe(II) to H2O2 molar ratioThe effect of Fe(II) to H2O2 molar ratio on removal of target

estrogens is illustrated in Fig. 1d. The rate of removal of targetcompounds increased when the molar ratio increased from0.0667 to 0.167. As the molar ratio increased to 0.25, removal effi-ciencies decreased. In all likelihood, more �OH radicals were gener-ated at high molar ratios, but �OH radicals were also scavenged byreacting with excess Fe(II) as shown in Eq. (8) (Bouasla et al., 2010).

Fe2þ þ �OH! Fe3þ þ OH� ð8Þ

Excess �OH radicals may react with themselves, as shown in Eq.(9) (Mendez-Arriaga et al., 2010).

HO� þHO� ! H2O2 ð9Þ

Therefore, extremely high Fe(II) to H2O2 molar ratio is not ben-eficial to the removal of estrogens.

The increase of Fe(II) to H2O2 molar ratio can also improve thesolubilization of the sludge (Fig. 2d). The �OH radicals generatedduring Fenton oxidation have an oxidizing potential of 2.8 V andare capable of oxidizing a wide range of organic compoundsincluding sludge cells which resulted in the increase of STOC anddecrease of TSS and VSS (Kavitha and Palanivelu, 2004). Resultsshow that the solubilization rate of the sludge increased with theincrease of Fe(II) to H2O2 molar ratio, but somewhat slowed downwhen the Fe(II) to H2O2 molar ratio reached above 0.167 (Fig. 2d).

Taking both estrogen removal and sludge solubilization intoconsideration, the Fe(II) to H2O2 molar ratio of 0.167 is recom-mended. The excess ferric ions formed in the process of Fenton oxi-dation can be further removed through precipitation and

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Fig. 1. Effects of H2O2 dosage (a), initial pH (b), reaction time (c), and Fe(II) to H2O2 molar ratio (d) on removal efficiencies of E1, E2, EE2, and E3. Data are means of threereplicates and error bars show standard deviations.

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polymerization, thus strengthen and improve the dewaterability ofsludge (Neyens and Baeyens, 2003).

As a result of the experimental findings, Fenton oxidation can beconsidered as a useful sludge pretreatment method. Under the fol-lowing recommended conditions: H2O2 dosage = 15.62 mmol g�1,initial pH = 3, reaction time = 60 min, and Fe(II) to H2O2 molar ra-tio = 0.167, the removal efficiencies of E1, E2, EE2, and E3 were70%, 90%, 84% and 98%, respectively; STOC increased by 24-fold,and the solubility increments of TSS and VSS were 12.6% and19.6%, respectively.

3.2. Verification of the role of the �OH radical

The removal efficiencies of E1, E2, EE2, and E3 with and withoutscavenger are shown in Fig. 3. Without scavenger, the removal

efficiencies of E1, E2, EE2, and E3 were 33%, 59%, 49% and 89%,respectively. With 0.5 M t-BuOH, the removal efficiencies of E1,E2, EE2, and E3 were only 3%, 2%, 4% and 4%, respectively. The addi-tion of t-BuOH significantly decreased the removal efficiencies ofthe target estrogens. This shows that the �OH radical took the mostimportant role during Fenton oxidation of estrogens in sludge.

3.3. Degradation intermediates of estrogens during Fenton oxidation

Table 1 shows the intermediates of tested estrogens during Fen-ton oxidation. 1,4-estradien-3-one (DEO), estra-1,3,5(10),9(11)-tetraene-3,17-diol (ETD-9), estrone (E1), and testosterone (TS)were also reported in previous studies in which other AOPs wereused to degrade E2 and EE2 in water (Ohko et al., 2002; Zhaoet al., 2008). However, pregn-4-ene-3,20-dione and pregn-4-en-20-yn-3-one were not previously observed. Generally, most endo-crine disruptors that have potent estrogenic activity also have phenolgroups, and compounds without phenol groups exhibit little estro-genic activity (Pereira et al., 2011). As shown in Table 1, the phenolstructures of the estrogens were mostly oxidized to cyclohexenonemoieties and quinone-like structures. TS is the intermediate of E1,EE2, and E3 formed during Fenton oxidation. It has a cyclohexe-none moiety instead of a phenol moiety. Its estrogenic activity ismuch weaker than that of the target compounds (Gaido et al.,1997). This rule was also true for pregn-4-ene-3,20-dione andpregn-4-en-20-yn-3-one. DEO has a quinone-like moiety insteadof a phenol moiety compared to E2. It might be formed by the addi-tion of �OH to E2 through the carbon atom at the aromatic ring, asindicated by frontier electron density calculations performed byOhko et al. (2002). The hydroxyl group of DEO, located at atomC10, increases the hydrophilicity of the molecule, decreases its

E1 E2 EE2 E30

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Fig. 3. Removal efficiencies of E1, E2, EE2, and E3 without scavenger versus with 0.5M scavenger during Fenton’s oxidation. Data are means of three replicates and errorbars show standard deviations.

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28 Y. Li, A. Zhang / Chemosphere 105 (2014) 24–30

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estrogenic activity. These products can subsequently undergo�OH and HO2

� attacks and become completely mineralized (Zhaoet al., 2008). Residual intermediates, such as ETD-9, might formwhen �OH attacks the aliphatic rings. These single aromatic inter-mediates are presumably further oxidized through ring-ruptur-ing reactions into aliphatic compounds containing acids andacetaldehyde (Zhao et al., 2008). The results indicated that theFenton oxidation products are less active than the original targetcompounds.

4. Conclusions

The removal of estrogens from WAS through Fenton oxidationwas investigated. The effects of H2O2 dosage, initial pH, reactiontime, and the Fe(II) to H2O2 molar ratio were studied. The properreaction conditions were recommended as follows: H2O2 dos-age = 15.62 mmol g�1, initial pH = 3, reaction time = 60 min,Fe(II) to H2O2 molar ratio = 0.167. Under these conditions, the re-moval efficiencies of E1, E2, EE2, and E3 were 70%, 90%, 84%, and98%, respectively; STOC increased by 24-fold, and the extent ofsolubilization of TSS and VSS was close to 13% and 20%, respec-tively. Experiments with t-BuOH indicated that �OH takes themost important role in Fenton oxidation of estrogens in sludge.

The degradation intermediates of tested estrogens during Fen-ton oxidation were determined by GC/MS. As indicated by thestructures of the intermediates, the phenol structures of targetcompounds were mostly oxidized to cyclohexenone moietiesand quinone-like structures, which indicated that estrogenicactivity had been weakened. Pregn-4-ene-3,20-dione andpregn-4-en-20-yn-3-one were observed for the first time. The re-sults show that Fenton oxidation could be useful for the treat-ment of sludge containing estrogens.

Acknowledgements

This work was supported by the National Hi-Tech Researchand Development Program of China (863) (2011AA060902) andScience and Technology Commission of Shanghai Municipality(STCSM) (11230700700).

Appendix A. Supplementary material

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.chemosphere.2013.10.043.

References

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312

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330

302

Y. Li, A. Zhang / Chemosphere 105 (2014) 24–30 29

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