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Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments
Science of the Total Environment xxx (xxxx) xxx
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Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments Concepción Abril, Juan Luis Santos ⇑, Julia Martín, Irene Aparicio, Esteban Alonso Departamento de Química Analítica, Escuela Politécnica Superior, Universidad de Sevilla, C/ Virgen de África, 7, E–41011 Sevilla, Spain
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The highest concentrations
corresponded to surfactants, biocides and UV filters. Anaerobic stabilization was the most effective treatment for the removal of EDCs. Biocides and BPA were not removed in any of the studied sludge treatments. After sludge application onto soils, only TCS involved environmental risks.
a r t i c l e
i n f o
Article history: Received 7 August 2019 Received in revised form 26 September 2019 Accepted 16 October 2019 Available online xxxx Editor: Paola Verlicchi Keywords: Endocrine disrupting compounds Sludge stabilization technologies Sorption Biodegradation Sludge environmental risks Sludge-amended soils
a b s t r a c t In this work, twenty-three endocrine disrupting compounds have been monitored in sludge from different stages of four sludge stabilization treatments (anaerobic digestion, aerobic digestion, composting and anaerobic stabilization ponds). Their occurrence and fate in sludge stabilization plants and their potential environmental risk in treated sludge and in treated sludge-amended soils have been evaluated. Monitored compounds were six perfluoroalkyl compounds (PFC), four anionic surfactants (sodium alkylsulfates), a plasticiser (bisphenol A (BPA)), four preservatives (parabens), six UV-filters (benzophenones) and two biocides (triclosan and triclocarban). Only two of the UV-filters were not detected in any of the 141 analysed samples. Anionic surfactants (mean concentrations up to 1673 ng/g dry matter (dm) for the sum of surfactants) were the compounds at the highest concentration levels followed by biocides (up to 512 ng/g dm) and UV-filters (up to 662 ng/g dm). The concentrations of anionic surfactants, preservatives and UV-filters decreased 78, 25 and 80%, respectively, after anaerobic digestion. The concentration of perfluorinated carboxylic acids only decreased after composting (80% reduction) whereas biocides and BPA were not affected by any of the studied treatments. Environmental risks (risk quotients > 1) were obtained for all compounds, except for triclocarban and sodium octadecylsulfate, in treated sludge. In treated sludge-amended soils, risk quotients were lower than 1 for all compounds except for triclosan. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction ⇑ Corresponding author at: Department of Analytical Chemistry, University of Seville, C/ Virgen de África, 7, 41011 Seville, Spain. E-mail address: [email protected] (J.L. Santos).
Currently, the most common sludge stabilization treatments are anaerobic digestion (applied in anaerobic treatment plants (AnTP)), aerobic digestion (applied in aerobic treatment plants (AeTP)),
https://doi.org/10.1016/j.scitotenv.2019.135048 0048-9697/Ó 2019 Elsevier B.V. All rights reserved.
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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composting (applied in composting plants (CP)) and, in small cities, anaerobic digestion in anaerobic stabilization ponds (AnSP) (Anjum et al., 2016, Martín et al., 2015). In Europe, 39% out of the 10.13 million tons dry matter (d.m.) annually generated of treated sludge are estimated to be spread on agricultural lands as fertilizer (Milieu et al., 2008). In some countries, sludge application onto soils is even higher than 60% (France: 70%; United Kingdom: 68%; Ireland: 63% (Milieu et al., 2008); Spain: 76% (MMARM, 2010)). However, sludge application onto soils can involve negative effects such as odours (Rincón et al., 2019) and contamination with pollutants sorbed into sludge from wastewater that can enter into the food chain (Zhang et al., 2015; Aparicio et al., 2018; Urra et al., 2019). To the date, the pollutants usually monitored in sludge have been metals ˇ erne et al., 2019), pesticides (Alonso et al., 2009; Arif et al 2018; C (Xu et al., 2018), polycyclic aromatic hydrocarbons (Mailler et al., 2014) and those included in the list of priority organic pollutants (Directive 39/2013/CE). Nevertheless, the information about the occurrence and fate of emerging concern pollutants in sludge treatment technologies is scarce and mainly focused on anaerobic digestion treatments (Stasinakis et al., 2012; Stasinakis et al., 2013). Moreover, only a few papers have compared the occurrence and fate of certain groups of emerging concern pollutants, such as surfactants (González et al., 2010; Cantarero et al., 2012), the plasticiser bisphenol A (Guerra et al., 2015), pharmaceuticals (Martín et al., 2012; Martín et al., 2015) and the biocide triclosan (Tohidi et al., 2017), in different sludge treatment technologies. Therefore, the aims of this work were i) to determine the occurrence and fate of six groups of endocrine disrupting compounds (Table S1) in sludge from anaerobic and aerobic treatment plants, composting plants and anaerobic stabilization ponds; ii) to compare the influence of the stabilization technologies on the concentrations of the target pollutants; iii) and to evaluate the potential environmental risks in treated sludge and in treated sludgeamended soils.
2. Materials and methods 2.1. Chemicals and reagents HPLC-grade acetonitrile (ACN), methanol (MeOH) and water were supplied by Romil (Barcelona, Spain). Analytical-grade ammonium acetate (98%) was provided by Panreac (Barcelona, Spain). Glacial acetic acid (HAc) was supplied by Scharlab (Barcelona, Spain). High purity standards of methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), benzylparaben (BzP), triclocarban (TCB), triclosan (TCS), bisphenol A (BPA), benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone3 (BP-3), benzophenone-6 (BP-6), benzophenone-8 (BP-8), 4hydroxybenzophenone (4-OH-BP), perfluorobutanoic acid (PFBuA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were supplied by SigmaAldrich (Steinheim, Germany). Sodium dodecylsulfate (AS-C12), sodium tetradecylsulfate (AS-C14), sodium hexadecylsulfate (ASC16) and sodium octadecylsulfate (AS-C18) were supplied by Alfa Aesar (Barcelona, Spain). The chemical structures and physical– chemical properties of the target compounds are shown in Table S1. Isotopically-labelled compounds, used as internal standards (I.S.), were supplied by Sigma-Aldrich (Steinheim, Germany) (EtP-d5, BP-d10, and BPA-d16) and by Cambridge Isotope Laboratories (MA, USA) (PFOA-13C4). C18 sorbent was provided by Scharlab (Barcelona, Spain). Individual stock solutions of each compound were prepared at 1000 lg mL1 in MeOH and stored at 18 °C. Working solutions were prepared by diluting the stock standard solutions in MeOH.
2.2. Sample collection and stabilization treatments Sludge samples were collected from four AnTPs, one CP, two AeTPs and three AnSPs located in the South of Spain. In Fig. 1, it can be seen treatment lines and types and characteristics of sludge sampled from each treatment plant. Characteristics of each plant can be seen in Table S2. Primary sludge (PS), secondary sludge (SS), mixed sludge (MS), anaerobically-digested and dehydrated sludge (AnDS)), aerobically-digested and dehydrated sludge (AeDS)) and composted sludge (CS) were monthly collected. Lagoon sludge (LS) was collected twice in a year, in January and in August, because of the high residence time of sludge in AnSPs (1–2 years) in comparison to the other types of sludge (1 month approximately). PS and SS were introduced in the same proportion in the anaerobic digestor. After digestion and dehydration, the AnDS generated in the four AnTPs were composted in the same CP by means of dynamic batteries thermally-controlled with aeration provided by turning. Two litres of PS, SS, MS, and LS and 1 kg of AnDS, AeDS and CS were collected in glass bottles. Samples were freeze-dried in a Cryodos-50 lyophilizer (Telstar, Terrasa, Spain), homogenized, crushed with a mortar and sieved (particle size <100 mm). When necessary, they were kept in glass bottles and maintained at 18 °C until analysis. 2.3. Analytical determination The analytical determination was carried according to a previously reported method (Abril et al., 2018). The method consisted on ultrasound-assisted extraction with 3 mL of MeOH:HAc (95:5, v/v), clean-up by dispersive solid-phase extraction (d-SPE) with 0.8 g of C18 and analytical determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Chromatographic analysis was performed using an Agilent 1200 series HPLC (Agilent, USA) coupled to a 6410 triple quadrupole (QqQ) mass spectrometer (MS) equipped with an electrospray ionization source (ESI). Chromatographic separation was carried out with a HALO C18 column (50 mm 4.6 mm i.d., 2.7 mm particle size) (Advanced Materials Technology, USA) protected with a HALO C18 guard column (4.6 5 mm, 2.7 m particle size (Advanced Materials Technology, USA) and thermostated at 25 °C. Mobile phase was composed by a 10 mM ammonium acetate aqueous solution and ACN. Gradient elution was carried out at a flow rate of 0.6 mL/min by a linear increase from 30% to 70% of ACN in 14 min; then to 80% ACN in 5 min, held for 6 min, and back to initial conditions by a linear decrease of ACN proportion from 80% to 30% in 1 min, held for 5 min for re-equilibration. The injection volume was 10 mL. MS parameters were as follows: capillary voltage, 3000 V; drying gas flow rate; 9 L/min; drying gas temperature; 350 °C; and nebulizer pressure; 40 psi. Detailed information on LC-MS/MS and method validation parameters can be found in Tables S3 and S4, respectively. 2.4. Quality control Procedural blanks and a matrix-matched calibration standard at a medium concentration level (100 ng g1 for each target compound) were injected every 10 samples in each batch of samples. 2.5. Ecotoxicological risk assessment Environmental risk assessment was carried out using risk quotients (RQ) according to the European Commission Technical Guideline Document (EC-TGD, 2003). RQ value for each compound in sludge was calculated as the ratio between its measured environmental concentration (MEC) and its predicted no-effect concentration (PNEC). The RQs for sludge-amended soils were calculated
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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Fig. 1. Sludge stabilization treatments and location of sampling points.
from the predicted environmental concentration (PEC) calculated from the equation. Eq. (1) (EC-TGD, 2003):
PEC soil ¼ MEC sludge APPLsludge =DEPTHsoil RHOsoil
ð1Þ
where MECsludge is the concentration (ng/g dm) of the organic pollutant measured in sewage sludge; APPLsludge is the sludge application rate (0.5 kg m2 for agricultural soils); DEPTHsoil is the mixing depth (0.20 m for agricultural soils); and RHOsoil is the bulk density of wet soil (1700 kg m3 for agricultural soils). PNECsoil were calculated from the PNECwater value and soil-water distribution coefficient (Kd) of each pollutant calculated from EC50. More information about PNECsoil calculation and calculated PNECsoil values can be found in Table S5. Risk levels were categorised from RQ values as: low risk (RQ values from 0.01 to 0.1), medium risk (RQ values between 0.1 and 1) and high risk (RQ values higher than 1) (Ding et al., 2018; Mungray et al., 2008). 3. Results and discussion 3.1. Distribution of organic pollutants in the evaluated sludge stabilization treatments The occurrence and fate of each group of pollutants in each type of sludge are shown as box-and-whisker plots in Fig. 2. Lines in each box correspond to the lower (5%), median (50%) and upper percentile (95%). The point inside each box shows the mean concentration whereas lines extending from each end of the box show the maximum and minimum concentration values. The highest mean concentrations in untreated sludge corresponded to the
anionic surfactants AS-C12 (1318 ng/g dm in PS, 3590 ng/g dm in MS, 2851 ng/g dm in AeDS and 2133 ng/g dm in LS) and AS-C18 (2361 ng/g dm in SS and 1027 ng/g dm in CS). In AnTPs, the highest mean concentrations of some groups of compounds, such as surfactants and biocides, were measured in SS (sum of mean concentrations: 6210 ng/g dm and 190 ng/g dm, respectively) whereas the highest mean concentrations of other groups, such as PFCs, and BPA, were measured in AnDS (sum of mean concentrations: 365 ng/g dm and 245 ng/g dm, respectively) (Fig. 2). In addition, as indicate the dash arrows in Fig. 2, the concentration of the surfactants and biocides decreased after anaerobic digestion (from 4331 ng/g dm (PS-SS mean value) to 964 ng/g dm (AnDS) and from 117 ng/g dm (PS-SS mean value) to 89 ng/g dm (AnDS), respectively) and increased after aerobic digestion in AeTPs (from 4790 ng/g dm (MS) to 7111 ng/g dm (AeDS) and from 7.0 ng/g dm (MS) to 94 ng/g dm (AeDS), respectively) whereas the concentrations of PFCs and BPA increased after anaerobic digestion (from 207 ng/g dm (PS-SS) to 365 ng/g dm (AnDS) and from 72 ng/g dm (PS-SS) to 245 ng/g dm (AnDS), respectively) and remained constant after aerobic digestion (from 270 ng/g dm (MS) to 272 ng/g dm (AeDS) and from 30 ng/g dm (MS) to 44 ng/g dm (AeDS), respectively) (Fig. 2). These facts can be explained, as described in detail in sections below, not only by a removal of the target compounds by the sludge treatment applied but also to their different sorption behaviour. Sorption onto sludge can be due to hydrophobic interactions and to electrostatic interactions that are conditioned by log Kow and pKa values of the target compounds (data in Table S1), and organic matter content (OM) and pH of sludge (data in Fig. 1) (Verlicchi et al., 2015). For instance, the higher concentrations of surfactants and biocides in SS than in PS can be
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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Concentration (ng/g dm)
AnTP
AeTP
CP
8000
AnSP Anionic surfactants
6000 4000 2000 0
Concentration (ng/g dm)
1000 Biocides 800 600 400 200 0
Concentration (ng/g dm)
1500 UV-Filters 1000
500
0
Concentration (ng/g dm)
600 Preservatives 450 300 150 0
Concentration (ng/g dm)
600 PFCs 450 300 150 0
Concentration (ng/g dm)
600 BPA 450 300 150 0 Primary sludge
Secondary sludge
Anaerobically digested and dehydrated sludge
Composted sludge
Mixed sludge
Aerobically digested and dehydrated sludge
Lagoon sludge
Fig. 2. Box-and-whisker plots of the concentrations of the pollutants in each sludge stabilization technology.
explained by their high log Kow values, in the range from 4.42 to 7.08 (Table S1), and the higher organic matter content of SS (79%) with respect to PS (67%) whereas UV-filters and
preservatives (log Kow values in the range from 1.91 to 3.82) were similarly retained in both types of sewage sludge. In addition, a strong sorption onto sludge can also affect the biodegradation of
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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the pollutant by reducing its bioavailability and, consequently, can result in an increase of the concentration of the most recalcitrant compounds after sludge treatment. This fact could explain the increase of the concentrations of PFCs and BPA after anaerobic digestion and the increase of concentrations of anionic surfactants, UV-filters after aerobic digestion (Fig. 2). 3.1.1. Anionic surfactants The occurrence and fate of each anionic surfactant in each sludge stabilization treatment are shown as box-and-whisker plots in Fig. S1. The sum of mean concentrations of AS-C12, AS-C14, ASC16 and AS-C18 in non-treated sludge (fresh sludge) were 2452, 6210, 4790 and 7111 ng/g dm in PS, SS, MS and LS, respectively. The distribution pattern of the surfactants in PS was similar to that in MS (AS-C12 > AS-C14 > AS-C16 > AS-C18) (Fig S1) and consistent with that used in detergent formulations (Kavitha et al., 2014; Morrall et al., 2006). Nevertheless, in SS, the highest concentrations corresponded to AS-C18 (mean value: 2639 ng/g dm). The different distribution pattern in SS (AS-C18 > AS-C12 ffi AS-C14 ffi AS-C16) could be explained by the higher organic matter content of SS (78.0–84.2%) in comparison to PS (65.8–69.1%), MS (59.0–66.8%) and LS (38.3–49.5%), what ease the sorption of AS-C18. AS-C18 is the anionic surfactant with the highest log Kow value (7.08) (Table S1). After sludge digestion, a different behaviour was observed depending on the anaerobic or aerobic conditions of the digestion process. Concentrations of the four anionic surfactants decreased after anaerobic digestion (Fig. S1) but aerobic treatments such as composting and, especially, aerobic digestion caused a decrease of the concentrations of the shorter chain surfactant (AS-C12) whereas the concentrations of AS-C14 were not affected and the concentrations of the longer chain surfactants (AS-C16 and AS-C18) increased. In the case of LS, the high concentrations (mean values: 2133, 1485, 617 and 924 ng/g dm for AS-C12, ASC14, AS-C16 and AS-C18, respectively) in comparison to PS, SS and MS could be explained by the high sludge age of LS what ease the accumulation of contaminants. 3.1.2. Biocides The occurrence and fate of TCB and TCS in each type of sludge are shown as box-and-whisker plots in Fig. S2. TCS was measured at higher concentrations than TCB what can be explained by its higher use in personal care products (Chen et al., 2019). Mean concentrations of TCS in PS, SS, MS and LS were 64.2, 439, 7.0 and 22.1 ng/g dm, respectively, while mean concentrations of TCB were 0.09, 2.27 and 0.22 ng/g dm in PS, SS and LS, respectively. TCB was not detected in MS. Mean concentrations of TCS in AnDS, CS and AeDS were 88 ng/g dm, 205 ng/g dm, and 93.4 ng/g dm, respectively. Mean concentrations of TCB in AnDS, CS and AeDS were 1.4 ng/g dm, 5.7 ng/g dm and 1.1 ng/g dm, respectively. The concentrations of TCS in this work are higher than those reported by Lehutso et al. (2017) in non-treated sludge (TCS: 3.65–15 ng/g and TCB: 3.65–1 1.8 ng/g) and in treated sludge (TCS: 2.1–7.8 ng/g and TCB: 1.2– 9.2 ng/g) from South Africa but much lower than those reported in sludge from China by Chen et al. (2019) (TCS: 4–4870 ng/g dm and TCB: 3–43300 ng/g dm) and Yu et al. (2011) (TCS: 1188 ng/g dm; TCB: 5088 ng/g dm). This variability can be explained by the different consumption pattern of personal care products where TCB and TCS are used as antimicrobial agents. The higher concentrations of TCB and TCS in SS (2.3 and 439 ng/g, respectively) than in PS (0.09 and 64.2 ng/g) can be due to the higher organic matter content of SS what ease their sorption as described above for anionic surfactants. TCS was detected in 95% of the SS samples at concentrations up to 426 ng/g dm. Concentrations of TCS and TCB increased from AnDS to CS and from MS to AeDS (Fig. S2). For instance, TCB was not detected in MS but was detected in 20% of AeDS samples at concentrations from 2.64 to 7.20 ng/g dm. The
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above-mentioned increase of concentrations could be explained by a poor removal of the TCB and TCS (recalcitrant compounds) under aerobic conditions (composting and AeD) together with the loss of weight of treated sludge by the removal of organic matter. 3.1.3. UV filters In Fig. S3 are shown box and whisker plots of the concentrations of the UV filters in sludge from AnTs, CPs, AeTs and AnSPs. BP-3 was the UV filter most frequently detected (in 95% of the analysed samples) whereas BP-6 and BP-8 were not detected in any of the analysed samples. The highest concentrations of UV filters corresponded to BP-3 and 4-OH-BP in PS (509 ng/g dm and 792 ng/g dm, respectively), to BP-3 in SS (669 ng/g dm) and to 4-OH-BP in AeDS (1089 ng/g dm). BP-3 has a high log Kow value (log Kow: 3.79) what can explain its high sorption onto sludge whereas 4OH-BP has been reported to be the most abundant benzophenone, with the highest concentrations, in influent wastewater (Wang et al., (2017)). Moreover, 4-OH-BP can be also generated by alkylphenol degradation, by the transformation of BP-3 into 4OH-BP in influent wastewater and by its excretion as a human metabolite of BP-3 (Wang and Kannan, 2017). As can be seen in Fig. 2, the sum of UV-filters decreased from PS (mean: 292 ng/g dm) and SS (mean: 161 ng/g dm) to AnDS (mean: 45 ng/g) and CS (mean: 26 ng/g dm). Nevertheless, in AeTPs it was observed an increase of the concentrations of the sum of UV-filters from 393 ng/g dm in MS to 637 ng/g in AeDS. Sum of UV-filters in LS (463 ng/g) were similar to that measured in PS, SS and MS. 3.1.4. Preservatives As can be seen in Fig. 2, the highest concentrations of parabens were found in sludge from AnSPs (mean concentration for the sum of MeP, EtP, PrP and BzP: 287 ng/g dm). In spite of the low log Kow values of the parabens (from 1.91 to 3.59) all of them, except EtP, were detected in all the types of sewage sludge analysed (Fig. S4). EtP was not detected in sludge prior digestion but was detected in two AnDS samples (69 ng/g dm and 55 ng/g dm). This fact could be explained by its persistence to degradation together with the loss of weigh of sewage sludge by the removal of organic matter resulting in an increase of the concentration after sludge digestion. Concentrations measured in this work are similar to those found in other studies carried out in Spain by Nieto et al. (2009) (MeP: 46–202 ng/g dm; EtP: not detected (nd); PrP: 6–7 ng/g dm; BzP: nd-5 ng/g), and in Korea by Liao et al. (2013) (MeP: 4.31–540 ng/ g dm; EtP: nd-2.12 ng/g dm; PrP: nd-32.5 ng/g; BzP: nd-2.89 ng/ g dm). The distribution pattern is similar to that reported by Núñez et al. (2008) in sediments and agricultural soils from Spain (MeP: 0.63–1.80 ng/g dm; EtP: 0.59–1.17 ng/g dm;PrP: 0.59–2.20 ng/g dm; BzP: nd-1.83 ng/g dm); by Lee et al. (2005) in influent (MeP: 0.10–1.47 ng/mL; EtP: 0.02–0.27 ng/mL; PrP: 0.2–2.43 ng/mL; BzP: 0.02–0.26 ng/mL) and effluent sewage sludge (MeP: 0.02–0.03 ng/mL; EtP: nd; PrP: nd-0.04 ng/mL; BzP: nd-0.01 ng/mL) from Canada and in wastewater (GonzálezMariño et al., 2011; Ma et al., 2018; Molins-Delgado et al., 2016;) in Guadiamar River basin in Spain (Garrido et al., 2016) and with their use in cosmetics and in food industry). After anaerobic digestion and composting, the concentrations of MeP and BzP decreased (MeP: from 38.5 ng/g dm in the mixture PS-SS to 26 ng/g in AnDS and 11 ng/g in CS; BzP: from 26.5 ng/g dm in the mixture PS-SS to 9 ng/g in AnDS and 6 ng/g in CS) whereas the concentration of PrP slightly increased (from 21 ng/g dm, in the mixture PS-SS, to 25 ng/g in AnDS and 38 ng/g in CS) (Fig S4). However, after aerobic digestion, the sum of the concentrations of parabens in AeDS (mean: 120 ng/g dm) was slightly higher than that in MS (mean: 72 ng/kg dm) being PrP and BzP the parabens with a higher increase from MS to AeDS (PrP: from 36 ng/g dm in MS to 52 ng/g dm in AeDS; BzP: mean
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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Preservatives
PFCs
100000,00
Biocides
BPA
Anionic surfactants
UV-Filters AnDS
10000,00 1000,00
Risk quotient
100,00 10,00 1,00 0,10 0,01 0,00 0,00 10000,00 AeDS 1000,00
Risk quotient
100,00 10,00 1,00 0,10 0,01 0,00 0,00 100000,00 Composted Sludge
10000,00 1000,00
Risk quotient
100,00 10,00 1,00 0,10 0,01 0,00 0,00 1000,00 Lagoon Sludge 100,00
Risk quotient
10,00 1,00 0,10 0,01 0,00 0,00
Fig. 3. Risk quotients (RQ) for treated sludge calculated from measured concentrations in sludge.
from 24 ng/g dm in MS to 61 ng/g dm in AeDS). The increase of concentrations of PrP and BzP after composting and after AeD could be explained by a poor degradation under aerobic conditions
together with a removal of the organic matter content of sludge resulting in an enhancement of the concentration of the parabens in aerobically-treated sludge.
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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Preservatives
PFCs
Biocides
BPA
Anionic Surfactants
UV-Filters
100,00 AnDS-amended soil Risk quotient
10,00 1,00 0,10 0,01 0,00 0,00 10,00
Risk quotient
AeDS-amended soil 1,00
0,10
0,01
0,00
0,00 100,00 Risk quotient
Composted sludge-amended soil 10,00 1,00 0,10 0,01 0,00 0,00
Risk quotient
10,00 Lagoon sludge-amended soil 1,00
0,10
0,01
0,00
0,00
Fig. 4. Risk quotients (RQ) for treated sludge-amended soils.
This fact contrasts with the better degradation of MeP and PrP under experimental aerobic conditions than under anaerobic conditions reported by Wu et al. (2017). However, the results obtained
in this work are consistent with the stability of MeP and PrP in sludge reported by Li et al. (2015). The highest concentrations of PrP and BzP were found in LS, in spite of the low volume of
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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wastewater treated in AnSPs. This fact can be explained by the high residence time of sludge in AnSP what promotes the accumulation of these compounds. 3.1.5. Perfluoroalkyl compounds The sum of mean concentrations of PFCs were up to 487, 446 and 299 ng/g dm in PS, SS and MS, respectively. A similar distribution pattern was found in all types of sludge (PFHxA > PFHpAPFPeA > PFBuA > PFOA > PFOS) (Fig. S5). In spite of the wide variability in PFC concentration reported from a sewage treatment plant to another (Arvaniti and Stasinakis, 2015; Campo et al., 2014) and from a sampling campaign to another (Campo et al., 2014), the distribution pattern in this work, except for PFOS and PFOA, is consistent with the higher tendency of longer PFCs to be sorbed onto sludge described by Arvaniti et al. (2015). Concentrations for PFOS and PFOA in this work are lower than those of shorter chain PFCs but are within the ranges from 5 to 160 ng/g dm and from 1 to 241 ng/g dm reported by Clarke and Smith (2011) for PFOS and PFOA, respectively, in three sludge treatment plants in USA and in another from Denmark. As can be seen in Fig S5, PFC concentrations increased after AnD and were maintained constant after AeD. This fact is consistent with the high stability provided by the extremely strong carbon-fluorine bonds in their chemical structures (Table S1) (Arvaniti and Stasinakis, 2015). Composting caused a decrease of the concentrations of perfluoroalkyl carboxylic acids but produced an increase of the concentrations of PFOS (Fig. S5). The increase of PFOS concentration after composting could be due to a poor degradation under aerobic conditions together with high decrease of organic matter content of sludge by composting. 3.1.6. BPA Concentrations of BPA in treated sludge were up to 579, 658 and 77 ng/g dm in AnDS, CS and AeDS, respectively (Fig. 2). BPA concentration increased after AnD (mean concentrations in PS, SS and AnDS: 45 ng/g dm, 100 ng/g dm and 245 ng/g dm, respectively) but decreased, or was maintained constant, after composting (from 245 ng/g in AnDS to 187 ng/g in CS) and AeD (from 30 ng/g dm in MS to 44 ng/g in AeDS) (Fig. 2). This fact reveals a poor degradation under anaerobic conditions and better degradation under aerobic conditions what allows maintaining its concentrations similar to those prior sludge treatment. These results are consistent with the poor removal rates of BPA in AnTPs reported by Samaras et al. (2013). The concentrations of BPA in this work are within the range from 4 ng/g dm to 1750 ng/g dm reported by Clarke and Smith (2011) in sewage sludge samples from Germany, Australia, Greece and China but lower than those reported by Petrie et al. (2019) in digested sludge from two treatment plants affected by industrial BPA discharges (4600 ng/g dm-38700 ng/g dm). 3.2. Environmental risk assessment The ecotoxicological risk was evaluated at two possible scenarios: the ecotoxicological risk in treated sludge generated in each stabilization treatment and the risks associated to treated-sludge application onto agricultural soils. In Fig. 3 and Fig. 4, it can be seen box and whisker plots representing RQ values corresponding to treated sludge and to treated sludge-amended soils, respectively. All the compounds, except TCB and AS-C18, imply ecotoxicological risk (mean RQ > 1) in sludge (Fig. 3). but, after sludge application onto soil, the ecotoxicological risks decreased to RQ values lower than 1, except for TCS (Fig. 4). RQ values higher than 1 were obtained for TCS in 40, 40, 50 and 5% of AnDS, AeDS CS and LS analysed samples. A high ecotoxicological risk due to 4-OH-BP was obtained after application onto soils of 95% of AeDS samples.
The obtained results are consistent with the scarce information about environmental risks reported for treated sludge-amended soils. For instance, Thomaidis et al. (2016) reported RQ > 1 for TCS and RQ < 1 for PFOS and PFOA in AnDS-amended soils. Verlicchi and Zambello (2015) also reported RQ > 1 for TCS in sludge-amended soils. In spite of the low RQ values obtained for PFCs, they have been reported to be persistent in soils (>6 months), to be ecologically bio accumulative and to probably enter into the human food chain (Clarke and Smith, 2011). On the other hand, the persistence in soils of other compounds such as TCS and TCB is uncertain although there are evidences of their ecological bioaccumulation and soil ecotoxicity (Clarke and Smith, 2011). 4. Conclusions The highest concentrations in untreated sludge were measured in SS and corresponded to anionic surfactants. Anionic surfactants were also the compounds at the highest concentration levels in all types of sludge. After anaerobic digestion, the concentrations of surfactants, biocides, UV-filters and preservatives were similar to that in untreated sludge whereas the concentrations of PFCs and BPA increased. Nevertheless, composting decreased the concentrations of such compounds (84% for PFCs and 23% for BPA). An increase of concentrations, in the range from 31 to 40%, except biocides (92%), was also observed for all the groups of compounds, after aerobic digestion. Different behaviour was observed for compounds belonging to the same group what could be explained by their different log Kow values what conditions their sorption onto sludge and, therefore, their bioavailability for degradation. Environmental risk assessment revealed environmental risk in treated sludge for 21 out of the 23 target compounds. This fact could involve negative effects on microorganisms responsible of sludge digestion treatments. Environmental risks in treated sludgeamended soils were limited to TCS in soils amended with AnDS, AeDS and CS and to 4-OH-BP in soils amended with AeDS. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2019.135048. References Abril, C., Santos, J.L., Malvar, J.L., Martín, J., Aparicio, I., Alonso, E., 2018. Determination of perfluorinated compounds, bisphenol A, anionic surfactants and personal care products in digested sludge, compost and soil by liquidchromatography-tandem mass spectrometry. J. Chromatogr. A. 1576, 34–41. https://doi.org/10.1016/j.chroma.2018.09.028. Alonso, E., Aparicio, I., Santos, J.L., Villar, P., Santos, A., 2009. Sequential extraction of metals from mixed and digested sludge from aerobic WWTPs sited in the south of Spain. Waste Manage. 29, 418–424. https://doi.org/10.1016/j. wasman.2008.01.009. Anjum, M., Al-Makishah, N.H., Barakat, M.A., 2016. Wastewater sludge stabilization using pre-treatment methods. Process Saf. Environ. 102, 615–632. https://doi. org/10.1016/j.psep.2016.05.022. Aparicio, I., Martín, J., Abril, C., Santos, J.L., Alonso, E., 2018. Determination of household and industrial chemicals, personal care products and hormones in leafy and root vegetables by liquid chromatography-tandem mass spectrometry. J. Chromatogr. A. 1533, 49–56. https://doi.org/10.1016/j. chroma.2017.12.011.re. Arif, M.S., Riaz, M., Shahzad, S.M., Yasmeen, T., Ashraf, M., Siddique, M., Mubarik, M. S., Bragazza, L., Buttler, A., 2018. Fresh and composted industrial sludge restore soil functions in surface soil of degraded agricultural land. Sci. Total Environ. 619–620, 517–527. Arvaniti, O.S., Stasinakis, A.S., 2015. Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Sci. Total Environ. 524–525, 81–92. https://doi.org/10.1016/j.scitotenv.2015.04.023. Campo, J., Masiá, A., Picó, Y., Farré, M., Barceló, D., 2014. Distribution and fate of perfluoroalkyl substances in Mediterranean Spanish sewage treatment plants. Sci. Total Environ. 472, 912–922. https://doi.org/10.1016/j.scitotenv. 2013.11.056.
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Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments Concepción Abril, Juan Luis Santos ⇑, Julia Martín, Irene Aparicio, Esteban Alonso Departamento de Química Analítica, Escuela Politécnica Superior, Universidad de Sevilla, C/ Virgen de África, 7, E–41011 Sevilla, Spain
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The highest concentrations
corresponded to surfactants, biocides and UV filters. Anaerobic stabilization was the most effective treatment for the removal of EDCs. Biocides and BPA were not removed in any of the studied sludge treatments. After sludge application onto soils, only TCS involved environmental risks.
a r t i c l e
i n f o
Article history: Received 7 August 2019 Received in revised form 26 September 2019 Accepted 16 October 2019 Available online xxxx Editor: Paola Verlicchi Keywords: Endocrine disrupting compounds Sludge stabilization technologies Sorption Biodegradation Sludge environmental risks Sludge-amended soils
a b s t r a c t In this work, twenty-three endocrine disrupting compounds have been monitored in sludge from different stages of four sludge stabilization treatments (anaerobic digestion, aerobic digestion, composting and anaerobic stabilization ponds). Their occurrence and fate in sludge stabilization plants and their potential environmental risk in treated sludge and in treated sludge-amended soils have been evaluated. Monitored compounds were six perfluoroalkyl compounds (PFC), four anionic surfactants (sodium alkylsulfates), a plasticiser (bisphenol A (BPA)), four preservatives (parabens), six UV-filters (benzophenones) and two biocides (triclosan and triclocarban). Only two of the UV-filters were not detected in any of the 141 analysed samples. Anionic surfactants (mean concentrations up to 1673 ng/g dry matter (dm) for the sum of surfactants) were the compounds at the highest concentration levels followed by biocides (up to 512 ng/g dm) and UV-filters (up to 662 ng/g dm). The concentrations of anionic surfactants, preservatives and UV-filters decreased 78, 25 and 80%, respectively, after anaerobic digestion. The concentration of perfluorinated carboxylic acids only decreased after composting (80% reduction) whereas biocides and BPA were not affected by any of the studied treatments. Environmental risks (risk quotients > 1) were obtained for all compounds, except for triclocarban and sodium octadecylsulfate, in treated sludge. In treated sludge-amended soils, risk quotients were lower than 1 for all compounds except for triclosan. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction ⇑ Corresponding author at: Department of Analytical Chemistry, University of Seville, C/ Virgen de África, 7, 41011 Seville, Spain. E-mail address: [email protected] (J.L. Santos).
Currently, the most common sludge stabilization treatments are anaerobic digestion (applied in anaerobic treatment plants (AnTP)), aerobic digestion (applied in aerobic treatment plants (AeTP)),
https://doi.org/10.1016/j.scitotenv.2019.135048 0048-9697/Ó 2019 Elsevier B.V. All rights reserved.
Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048
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composting (applied in composting plants (CP)) and, in small cities, anaerobic digestion in anaerobic stabilization ponds (AnSP) (Anjum et al., 2016, Martín et al., 2015). In Europe, 39% out of the 10.13 million tons dry matter (d.m.) annually generated of treated sludge are estimated to be spread on agricultural lands as fertilizer (Milieu et al., 2008). In some countries, sludge application onto soils is even higher than 60% (France: 70%; United Kingdom: 68%; Ireland: 63% (Milieu et al., 2008); Spain: 76% (MMARM, 2010)). However, sludge application onto soils can involve negative effects such as odours (Rincón et al., 2019) and contamination with pollutants sorbed into sludge from wastewater that can enter into the food chain (Zhang et al., 2015; Aparicio et al., 2018; Urra et al., 2019). To the date, the pollutants usually monitored in sludge have been metals ˇ erne et al., 2019), pesticides (Alonso et al., 2009; Arif et al 2018; C (Xu et al., 2018), polycyclic aromatic hydrocarbons (Mailler et al., 2014) and those included in the list of priority organic pollutants (Directive 39/2013/CE). Nevertheless, the information about the occurrence and fate of emerging concern pollutants in sludge treatment technologies is scarce and mainly focused on anaerobic digestion treatments (Stasinakis et al., 2012; Stasinakis et al., 2013). Moreover, only a few papers have compared the occurrence and fate of certain groups of emerging concern pollutants, such as surfactants (González et al., 2010; Cantarero et al., 2012), the plasticiser bisphenol A (Guerra et al., 2015), pharmaceuticals (Martín et al., 2012; Martín et al., 2015) and the biocide triclosan (Tohidi et al., 2017), in different sludge treatment technologies. Therefore, the aims of this work were i) to determine the occurrence and fate of six groups of endocrine disrupting compounds (Table S1) in sludge from anaerobic and aerobic treatment plants, composting plants and anaerobic stabilization ponds; ii) to compare the influence of the stabilization technologies on the concentrations of the target pollutants; iii) and to evaluate the potential environmental risks in treated sludge and in treated sludgeamended soils.
2. Materials and methods 2.1. Chemicals and reagents HPLC-grade acetonitrile (ACN), methanol (MeOH) and water were supplied by Romil (Barcelona, Spain). Analytical-grade ammonium acetate (98%) was provided by Panreac (Barcelona, Spain). Glacial acetic acid (HAc) was supplied by Scharlab (Barcelona, Spain). High purity standards of methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), benzylparaben (BzP), triclocarban (TCB), triclosan (TCS), bisphenol A (BPA), benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone3 (BP-3), benzophenone-6 (BP-6), benzophenone-8 (BP-8), 4hydroxybenzophenone (4-OH-BP), perfluorobutanoic acid (PFBuA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were supplied by SigmaAldrich (Steinheim, Germany). Sodium dodecylsulfate (AS-C12), sodium tetradecylsulfate (AS-C14), sodium hexadecylsulfate (ASC16) and sodium octadecylsulfate (AS-C18) were supplied by Alfa Aesar (Barcelona, Spain). The chemical structures and physical– chemical properties of the target compounds are shown in Table S1. Isotopically-labelled compounds, used as internal standards (I.S.), were supplied by Sigma-Aldrich (Steinheim, Germany) (EtP-d5, BP-d10, and BPA-d16) and by Cambridge Isotope Laboratories (MA, USA) (PFOA-13C4). C18 sorbent was provided by Scharlab (Barcelona, Spain). Individual stock solutions of each compound were prepared at 1000 lg mL1 in MeOH and stored at 18 °C. Working solutions were prepared by diluting the stock standard solutions in MeOH.
2.2. Sample collection and stabilization treatments Sludge samples were collected from four AnTPs, one CP, two AeTPs and three AnSPs located in the South of Spain. In Fig. 1, it can be seen treatment lines and types and characteristics of sludge sampled from each treatment plant. Characteristics of each plant can be seen in Table S2. Primary sludge (PS), secondary sludge (SS), mixed sludge (MS), anaerobically-digested and dehydrated sludge (AnDS)), aerobically-digested and dehydrated sludge (AeDS)) and composted sludge (CS) were monthly collected. Lagoon sludge (LS) was collected twice in a year, in January and in August, because of the high residence time of sludge in AnSPs (1–2 years) in comparison to the other types of sludge (1 month approximately). PS and SS were introduced in the same proportion in the anaerobic digestor. After digestion and dehydration, the AnDS generated in the four AnTPs were composted in the same CP by means of dynamic batteries thermally-controlled with aeration provided by turning. Two litres of PS, SS, MS, and LS and 1 kg of AnDS, AeDS and CS were collected in glass bottles. Samples were freeze-dried in a Cryodos-50 lyophilizer (Telstar, Terrasa, Spain), homogenized, crushed with a mortar and sieved (particle size <100 mm). When necessary, they were kept in glass bottles and maintained at 18 °C until analysis. 2.3. Analytical determination The analytical determination was carried according to a previously reported method (Abril et al., 2018). The method consisted on ultrasound-assisted extraction with 3 mL of MeOH:HAc (95:5, v/v), clean-up by dispersive solid-phase extraction (d-SPE) with 0.8 g of C18 and analytical determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Chromatographic analysis was performed using an Agilent 1200 series HPLC (Agilent, USA) coupled to a 6410 triple quadrupole (QqQ) mass spectrometer (MS) equipped with an electrospray ionization source (ESI). Chromatographic separation was carried out with a HALO C18 column (50 mm 4.6 mm i.d., 2.7 mm particle size) (Advanced Materials Technology, USA) protected with a HALO C18 guard column (4.6 5 mm, 2.7 m particle size (Advanced Materials Technology, USA) and thermostated at 25 °C. Mobile phase was composed by a 10 mM ammonium acetate aqueous solution and ACN. Gradient elution was carried out at a flow rate of 0.6 mL/min by a linear increase from 30% to 70% of ACN in 14 min; then to 80% ACN in 5 min, held for 6 min, and back to initial conditions by a linear decrease of ACN proportion from 80% to 30% in 1 min, held for 5 min for re-equilibration. The injection volume was 10 mL. MS parameters were as follows: capillary voltage, 3000 V; drying gas flow rate; 9 L/min; drying gas temperature; 350 °C; and nebulizer pressure; 40 psi. Detailed information on LC-MS/MS and method validation parameters can be found in Tables S3 and S4, respectively. 2.4. Quality control Procedural blanks and a matrix-matched calibration standard at a medium concentration level (100 ng g1 for each target compound) were injected every 10 samples in each batch of samples. 2.5. Ecotoxicological risk assessment Environmental risk assessment was carried out using risk quotients (RQ) according to the European Commission Technical Guideline Document (EC-TGD, 2003). RQ value for each compound in sludge was calculated as the ratio between its measured environmental concentration (MEC) and its predicted no-effect concentration (PNEC). The RQs for sludge-amended soils were calculated
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Fig. 1. Sludge stabilization treatments and location of sampling points.
from the predicted environmental concentration (PEC) calculated from the equation. Eq. (1) (EC-TGD, 2003):
PEC soil ¼ MEC sludge APPLsludge =DEPTHsoil RHOsoil
ð1Þ
where MECsludge is the concentration (ng/g dm) of the organic pollutant measured in sewage sludge; APPLsludge is the sludge application rate (0.5 kg m2 for agricultural soils); DEPTHsoil is the mixing depth (0.20 m for agricultural soils); and RHOsoil is the bulk density of wet soil (1700 kg m3 for agricultural soils). PNECsoil were calculated from the PNECwater value and soil-water distribution coefficient (Kd) of each pollutant calculated from EC50. More information about PNECsoil calculation and calculated PNECsoil values can be found in Table S5. Risk levels were categorised from RQ values as: low risk (RQ values from 0.01 to 0.1), medium risk (RQ values between 0.1 and 1) and high risk (RQ values higher than 1) (Ding et al., 2018; Mungray et al., 2008). 3. Results and discussion 3.1. Distribution of organic pollutants in the evaluated sludge stabilization treatments The occurrence and fate of each group of pollutants in each type of sludge are shown as box-and-whisker plots in Fig. 2. Lines in each box correspond to the lower (5%), median (50%) and upper percentile (95%). The point inside each box shows the mean concentration whereas lines extending from each end of the box show the maximum and minimum concentration values. The highest mean concentrations in untreated sludge corresponded to the
anionic surfactants AS-C12 (1318 ng/g dm in PS, 3590 ng/g dm in MS, 2851 ng/g dm in AeDS and 2133 ng/g dm in LS) and AS-C18 (2361 ng/g dm in SS and 1027 ng/g dm in CS). In AnTPs, the highest mean concentrations of some groups of compounds, such as surfactants and biocides, were measured in SS (sum of mean concentrations: 6210 ng/g dm and 190 ng/g dm, respectively) whereas the highest mean concentrations of other groups, such as PFCs, and BPA, were measured in AnDS (sum of mean concentrations: 365 ng/g dm and 245 ng/g dm, respectively) (Fig. 2). In addition, as indicate the dash arrows in Fig. 2, the concentration of the surfactants and biocides decreased after anaerobic digestion (from 4331 ng/g dm (PS-SS mean value) to 964 ng/g dm (AnDS) and from 117 ng/g dm (PS-SS mean value) to 89 ng/g dm (AnDS), respectively) and increased after aerobic digestion in AeTPs (from 4790 ng/g dm (MS) to 7111 ng/g dm (AeDS) and from 7.0 ng/g dm (MS) to 94 ng/g dm (AeDS), respectively) whereas the concentrations of PFCs and BPA increased after anaerobic digestion (from 207 ng/g dm (PS-SS) to 365 ng/g dm (AnDS) and from 72 ng/g dm (PS-SS) to 245 ng/g dm (AnDS), respectively) and remained constant after aerobic digestion (from 270 ng/g dm (MS) to 272 ng/g dm (AeDS) and from 30 ng/g dm (MS) to 44 ng/g dm (AeDS), respectively) (Fig. 2). These facts can be explained, as described in detail in sections below, not only by a removal of the target compounds by the sludge treatment applied but also to their different sorption behaviour. Sorption onto sludge can be due to hydrophobic interactions and to electrostatic interactions that are conditioned by log Kow and pKa values of the target compounds (data in Table S1), and organic matter content (OM) and pH of sludge (data in Fig. 1) (Verlicchi et al., 2015). For instance, the higher concentrations of surfactants and biocides in SS than in PS can be
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Concentration (ng/g dm)
AnTP
AeTP
CP
8000
AnSP Anionic surfactants
6000 4000 2000 0
Concentration (ng/g dm)
1000 Biocides 800 600 400 200 0
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600 BPA 450 300 150 0 Primary sludge
Secondary sludge
Anaerobically digested and dehydrated sludge
Composted sludge
Mixed sludge
Aerobically digested and dehydrated sludge
Lagoon sludge
Fig. 2. Box-and-whisker plots of the concentrations of the pollutants in each sludge stabilization technology.
explained by their high log Kow values, in the range from 4.42 to 7.08 (Table S1), and the higher organic matter content of SS (79%) with respect to PS (67%) whereas UV-filters and
preservatives (log Kow values in the range from 1.91 to 3.82) were similarly retained in both types of sewage sludge. In addition, a strong sorption onto sludge can also affect the biodegradation of
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the pollutant by reducing its bioavailability and, consequently, can result in an increase of the concentration of the most recalcitrant compounds after sludge treatment. This fact could explain the increase of the concentrations of PFCs and BPA after anaerobic digestion and the increase of concentrations of anionic surfactants, UV-filters after aerobic digestion (Fig. 2). 3.1.1. Anionic surfactants The occurrence and fate of each anionic surfactant in each sludge stabilization treatment are shown as box-and-whisker plots in Fig. S1. The sum of mean concentrations of AS-C12, AS-C14, ASC16 and AS-C18 in non-treated sludge (fresh sludge) were 2452, 6210, 4790 and 7111 ng/g dm in PS, SS, MS and LS, respectively. The distribution pattern of the surfactants in PS was similar to that in MS (AS-C12 > AS-C14 > AS-C16 > AS-C18) (Fig S1) and consistent with that used in detergent formulations (Kavitha et al., 2014; Morrall et al., 2006). Nevertheless, in SS, the highest concentrations corresponded to AS-C18 (mean value: 2639 ng/g dm). The different distribution pattern in SS (AS-C18 > AS-C12 ffi AS-C14 ffi AS-C16) could be explained by the higher organic matter content of SS (78.0–84.2%) in comparison to PS (65.8–69.1%), MS (59.0–66.8%) and LS (38.3–49.5%), what ease the sorption of AS-C18. AS-C18 is the anionic surfactant with the highest log Kow value (7.08) (Table S1). After sludge digestion, a different behaviour was observed depending on the anaerobic or aerobic conditions of the digestion process. Concentrations of the four anionic surfactants decreased after anaerobic digestion (Fig. S1) but aerobic treatments such as composting and, especially, aerobic digestion caused a decrease of the concentrations of the shorter chain surfactant (AS-C12) whereas the concentrations of AS-C14 were not affected and the concentrations of the longer chain surfactants (AS-C16 and AS-C18) increased. In the case of LS, the high concentrations (mean values: 2133, 1485, 617 and 924 ng/g dm for AS-C12, ASC14, AS-C16 and AS-C18, respectively) in comparison to PS, SS and MS could be explained by the high sludge age of LS what ease the accumulation of contaminants. 3.1.2. Biocides The occurrence and fate of TCB and TCS in each type of sludge are shown as box-and-whisker plots in Fig. S2. TCS was measured at higher concentrations than TCB what can be explained by its higher use in personal care products (Chen et al., 2019). Mean concentrations of TCS in PS, SS, MS and LS were 64.2, 439, 7.0 and 22.1 ng/g dm, respectively, while mean concentrations of TCB were 0.09, 2.27 and 0.22 ng/g dm in PS, SS and LS, respectively. TCB was not detected in MS. Mean concentrations of TCS in AnDS, CS and AeDS were 88 ng/g dm, 205 ng/g dm, and 93.4 ng/g dm, respectively. Mean concentrations of TCB in AnDS, CS and AeDS were 1.4 ng/g dm, 5.7 ng/g dm and 1.1 ng/g dm, respectively. The concentrations of TCS in this work are higher than those reported by Lehutso et al. (2017) in non-treated sludge (TCS: 3.65–15 ng/g and TCB: 3.65–1 1.8 ng/g) and in treated sludge (TCS: 2.1–7.8 ng/g and TCB: 1.2– 9.2 ng/g) from South Africa but much lower than those reported in sludge from China by Chen et al. (2019) (TCS: 4–4870 ng/g dm and TCB: 3–43300 ng/g dm) and Yu et al. (2011) (TCS: 1188 ng/g dm; TCB: 5088 ng/g dm). This variability can be explained by the different consumption pattern of personal care products where TCB and TCS are used as antimicrobial agents. The higher concentrations of TCB and TCS in SS (2.3 and 439 ng/g, respectively) than in PS (0.09 and 64.2 ng/g) can be due to the higher organic matter content of SS what ease their sorption as described above for anionic surfactants. TCS was detected in 95% of the SS samples at concentrations up to 426 ng/g dm. Concentrations of TCS and TCB increased from AnDS to CS and from MS to AeDS (Fig. S2). For instance, TCB was not detected in MS but was detected in 20% of AeDS samples at concentrations from 2.64 to 7.20 ng/g dm. The
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above-mentioned increase of concentrations could be explained by a poor removal of the TCB and TCS (recalcitrant compounds) under aerobic conditions (composting and AeD) together with the loss of weight of treated sludge by the removal of organic matter. 3.1.3. UV filters In Fig. S3 are shown box and whisker plots of the concentrations of the UV filters in sludge from AnTs, CPs, AeTs and AnSPs. BP-3 was the UV filter most frequently detected (in 95% of the analysed samples) whereas BP-6 and BP-8 were not detected in any of the analysed samples. The highest concentrations of UV filters corresponded to BP-3 and 4-OH-BP in PS (509 ng/g dm and 792 ng/g dm, respectively), to BP-3 in SS (669 ng/g dm) and to 4-OH-BP in AeDS (1089 ng/g dm). BP-3 has a high log Kow value (log Kow: 3.79) what can explain its high sorption onto sludge whereas 4OH-BP has been reported to be the most abundant benzophenone, with the highest concentrations, in influent wastewater (Wang et al., (2017)). Moreover, 4-OH-BP can be also generated by alkylphenol degradation, by the transformation of BP-3 into 4OH-BP in influent wastewater and by its excretion as a human metabolite of BP-3 (Wang and Kannan, 2017). As can be seen in Fig. 2, the sum of UV-filters decreased from PS (mean: 292 ng/g dm) and SS (mean: 161 ng/g dm) to AnDS (mean: 45 ng/g) and CS (mean: 26 ng/g dm). Nevertheless, in AeTPs it was observed an increase of the concentrations of the sum of UV-filters from 393 ng/g dm in MS to 637 ng/g in AeDS. Sum of UV-filters in LS (463 ng/g) were similar to that measured in PS, SS and MS. 3.1.4. Preservatives As can be seen in Fig. 2, the highest concentrations of parabens were found in sludge from AnSPs (mean concentration for the sum of MeP, EtP, PrP and BzP: 287 ng/g dm). In spite of the low log Kow values of the parabens (from 1.91 to 3.59) all of them, except EtP, were detected in all the types of sewage sludge analysed (Fig. S4). EtP was not detected in sludge prior digestion but was detected in two AnDS samples (69 ng/g dm and 55 ng/g dm). This fact could be explained by its persistence to degradation together with the loss of weigh of sewage sludge by the removal of organic matter resulting in an increase of the concentration after sludge digestion. Concentrations measured in this work are similar to those found in other studies carried out in Spain by Nieto et al. (2009) (MeP: 46–202 ng/g dm; EtP: not detected (nd); PrP: 6–7 ng/g dm; BzP: nd-5 ng/g), and in Korea by Liao et al. (2013) (MeP: 4.31–540 ng/ g dm; EtP: nd-2.12 ng/g dm; PrP: nd-32.5 ng/g; BzP: nd-2.89 ng/ g dm). The distribution pattern is similar to that reported by Núñez et al. (2008) in sediments and agricultural soils from Spain (MeP: 0.63–1.80 ng/g dm; EtP: 0.59–1.17 ng/g dm;PrP: 0.59–2.20 ng/g dm; BzP: nd-1.83 ng/g dm); by Lee et al. (2005) in influent (MeP: 0.10–1.47 ng/mL; EtP: 0.02–0.27 ng/mL; PrP: 0.2–2.43 ng/mL; BzP: 0.02–0.26 ng/mL) and effluent sewage sludge (MeP: 0.02–0.03 ng/mL; EtP: nd; PrP: nd-0.04 ng/mL; BzP: nd-0.01 ng/mL) from Canada and in wastewater (GonzálezMariño et al., 2011; Ma et al., 2018; Molins-Delgado et al., 2016;) in Guadiamar River basin in Spain (Garrido et al., 2016) and with their use in cosmetics and in food industry). After anaerobic digestion and composting, the concentrations of MeP and BzP decreased (MeP: from 38.5 ng/g dm in the mixture PS-SS to 26 ng/g in AnDS and 11 ng/g in CS; BzP: from 26.5 ng/g dm in the mixture PS-SS to 9 ng/g in AnDS and 6 ng/g in CS) whereas the concentration of PrP slightly increased (from 21 ng/g dm, in the mixture PS-SS, to 25 ng/g in AnDS and 38 ng/g in CS) (Fig S4). However, after aerobic digestion, the sum of the concentrations of parabens in AeDS (mean: 120 ng/g dm) was slightly higher than that in MS (mean: 72 ng/kg dm) being PrP and BzP the parabens with a higher increase from MS to AeDS (PrP: from 36 ng/g dm in MS to 52 ng/g dm in AeDS; BzP: mean
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Preservatives
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Fig. 3. Risk quotients (RQ) for treated sludge calculated from measured concentrations in sludge.
from 24 ng/g dm in MS to 61 ng/g dm in AeDS). The increase of concentrations of PrP and BzP after composting and after AeD could be explained by a poor degradation under aerobic conditions
together with a removal of the organic matter content of sludge resulting in an enhancement of the concentration of the parabens in aerobically-treated sludge.
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Preservatives
PFCs
Biocides
BPA
Anionic Surfactants
UV-Filters
100,00 AnDS-amended soil Risk quotient
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Fig. 4. Risk quotients (RQ) for treated sludge-amended soils.
This fact contrasts with the better degradation of MeP and PrP under experimental aerobic conditions than under anaerobic conditions reported by Wu et al. (2017). However, the results obtained
in this work are consistent with the stability of MeP and PrP in sludge reported by Li et al. (2015). The highest concentrations of PrP and BzP were found in LS, in spite of the low volume of
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wastewater treated in AnSPs. This fact can be explained by the high residence time of sludge in AnSP what promotes the accumulation of these compounds. 3.1.5. Perfluoroalkyl compounds The sum of mean concentrations of PFCs were up to 487, 446 and 299 ng/g dm in PS, SS and MS, respectively. A similar distribution pattern was found in all types of sludge (PFHxA > PFHpAPFPeA > PFBuA > PFOA > PFOS) (Fig. S5). In spite of the wide variability in PFC concentration reported from a sewage treatment plant to another (Arvaniti and Stasinakis, 2015; Campo et al., 2014) and from a sampling campaign to another (Campo et al., 2014), the distribution pattern in this work, except for PFOS and PFOA, is consistent with the higher tendency of longer PFCs to be sorbed onto sludge described by Arvaniti et al. (2015). Concentrations for PFOS and PFOA in this work are lower than those of shorter chain PFCs but are within the ranges from 5 to 160 ng/g dm and from 1 to 241 ng/g dm reported by Clarke and Smith (2011) for PFOS and PFOA, respectively, in three sludge treatment plants in USA and in another from Denmark. As can be seen in Fig S5, PFC concentrations increased after AnD and were maintained constant after AeD. This fact is consistent with the high stability provided by the extremely strong carbon-fluorine bonds in their chemical structures (Table S1) (Arvaniti and Stasinakis, 2015). Composting caused a decrease of the concentrations of perfluoroalkyl carboxylic acids but produced an increase of the concentrations of PFOS (Fig. S5). The increase of PFOS concentration after composting could be due to a poor degradation under aerobic conditions together with high decrease of organic matter content of sludge by composting. 3.1.6. BPA Concentrations of BPA in treated sludge were up to 579, 658 and 77 ng/g dm in AnDS, CS and AeDS, respectively (Fig. 2). BPA concentration increased after AnD (mean concentrations in PS, SS and AnDS: 45 ng/g dm, 100 ng/g dm and 245 ng/g dm, respectively) but decreased, or was maintained constant, after composting (from 245 ng/g in AnDS to 187 ng/g in CS) and AeD (from 30 ng/g dm in MS to 44 ng/g in AeDS) (Fig. 2). This fact reveals a poor degradation under anaerobic conditions and better degradation under aerobic conditions what allows maintaining its concentrations similar to those prior sludge treatment. These results are consistent with the poor removal rates of BPA in AnTPs reported by Samaras et al. (2013). The concentrations of BPA in this work are within the range from 4 ng/g dm to 1750 ng/g dm reported by Clarke and Smith (2011) in sewage sludge samples from Germany, Australia, Greece and China but lower than those reported by Petrie et al. (2019) in digested sludge from two treatment plants affected by industrial BPA discharges (4600 ng/g dm-38700 ng/g dm). 3.2. Environmental risk assessment The ecotoxicological risk was evaluated at two possible scenarios: the ecotoxicological risk in treated sludge generated in each stabilization treatment and the risks associated to treated-sludge application onto agricultural soils. In Fig. 3 and Fig. 4, it can be seen box and whisker plots representing RQ values corresponding to treated sludge and to treated sludge-amended soils, respectively. All the compounds, except TCB and AS-C18, imply ecotoxicological risk (mean RQ > 1) in sludge (Fig. 3). but, after sludge application onto soil, the ecotoxicological risks decreased to RQ values lower than 1, except for TCS (Fig. 4). RQ values higher than 1 were obtained for TCS in 40, 40, 50 and 5% of AnDS, AeDS CS and LS analysed samples. A high ecotoxicological risk due to 4-OH-BP was obtained after application onto soils of 95% of AeDS samples.
The obtained results are consistent with the scarce information about environmental risks reported for treated sludge-amended soils. For instance, Thomaidis et al. (2016) reported RQ > 1 for TCS and RQ < 1 for PFOS and PFOA in AnDS-amended soils. Verlicchi and Zambello (2015) also reported RQ > 1 for TCS in sludge-amended soils. In spite of the low RQ values obtained for PFCs, they have been reported to be persistent in soils (>6 months), to be ecologically bio accumulative and to probably enter into the human food chain (Clarke and Smith, 2011). On the other hand, the persistence in soils of other compounds such as TCS and TCB is uncertain although there are evidences of their ecological bioaccumulation and soil ecotoxicity (Clarke and Smith, 2011). 4. Conclusions The highest concentrations in untreated sludge were measured in SS and corresponded to anionic surfactants. Anionic surfactants were also the compounds at the highest concentration levels in all types of sludge. After anaerobic digestion, the concentrations of surfactants, biocides, UV-filters and preservatives were similar to that in untreated sludge whereas the concentrations of PFCs and BPA increased. Nevertheless, composting decreased the concentrations of such compounds (84% for PFCs and 23% for BPA). An increase of concentrations, in the range from 31 to 40%, except biocides (92%), was also observed for all the groups of compounds, after aerobic digestion. Different behaviour was observed for compounds belonging to the same group what could be explained by their different log Kow values what conditions their sorption onto sludge and, therefore, their bioavailability for degradation. Environmental risk assessment revealed environmental risk in treated sludge for 21 out of the 23 target compounds. This fact could involve negative effects on microorganisms responsible of sludge digestion treatments. Environmental risks in treated sludgeamended soils were limited to TCS in soils amended with AnDS, AeDS and CS and to 4-OH-BP in soils amended with AeDS. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2019.135048. References Abril, C., Santos, J.L., Malvar, J.L., Martín, J., Aparicio, I., Alonso, E., 2018. Determination of perfluorinated compounds, bisphenol A, anionic surfactants and personal care products in digested sludge, compost and soil by liquidchromatography-tandem mass spectrometry. J. Chromatogr. A. 1576, 34–41. https://doi.org/10.1016/j.chroma.2018.09.028. Alonso, E., Aparicio, I., Santos, J.L., Villar, P., Santos, A., 2009. Sequential extraction of metals from mixed and digested sludge from aerobic WWTPs sited in the south of Spain. Waste Manage. 29, 418–424. https://doi.org/10.1016/j. wasman.2008.01.009. Anjum, M., Al-Makishah, N.H., Barakat, M.A., 2016. Wastewater sludge stabilization using pre-treatment methods. Process Saf. Environ. 102, 615–632. https://doi. org/10.1016/j.psep.2016.05.022. Aparicio, I., Martín, J., Abril, C., Santos, J.L., Alonso, E., 2018. Determination of household and industrial chemicals, personal care products and hormones in leafy and root vegetables by liquid chromatography-tandem mass spectrometry. J. Chromatogr. A. 1533, 49–56. https://doi.org/10.1016/j. chroma.2017.12.011.re. Arif, M.S., Riaz, M., Shahzad, S.M., Yasmeen, T., Ashraf, M., Siddique, M., Mubarik, M. S., Bragazza, L., Buttler, A., 2018. Fresh and composted industrial sludge restore soil functions in surface soil of degraded agricultural land. Sci. Total Environ. 619–620, 517–527. Arvaniti, O.S., Stasinakis, A.S., 2015. Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Sci. Total Environ. 524–525, 81–92. https://doi.org/10.1016/j.scitotenv.2015.04.023. Campo, J., Masiá, A., Picó, Y., Farré, M., Barceló, D., 2014. Distribution and fate of perfluoroalkyl substances in Mediterranean Spanish sewage treatment plants. Sci. Total Environ. 472, 912–922. https://doi.org/10.1016/j.scitotenv. 2013.11.056.
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Please cite this article as: C. Abril, J. L. Santos, J. Martín et al., Occurrence, fate and environmental risk of anionic surfactants, bisphenol A, perfluorinated compounds and personal care products in sludge stabilization treatments, Science of the Total Environment, https://doi.org/10.1016/j. scitotenv.2019.135048