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Occurrence of phthalates in surface runoff, untreated and treated wastewater and fate during wastewater treatment
Chemosphere 78 (2010) 1078–1084
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Occurrence of phthalates in surface runoff, untreated and treated wastewater and fate during wastewater treatment M. Clara a,*, G. Windhofer a, W. Hartl a, K. Braun a, M. Simon a, O. Gans a, C. Scheffknecht b, A. Chovanec a a b
Umweltbundesamt GmbH, Spittelauer Lände 5, 1090 Vienna, Austria Environmental Institute of the State of Vorarlberg, Montfortstraße 4, 6901 Bregenz, Austria
a r t i c l e
i n f o
Article history: Received 9 October 2009 Received in revised form 21 December 2009 Accepted 22 December 2009 Available online 22 January 2010 Keywords: Phthalates Surface waters Surface runoff Wastewater Sewage sludge Wastewater treatment
a b s t r a c t Dimethyl phthalate, diethyl phthalate, dibuthyl phthalate, butylbenzyl phthalate, bis(2-ethylbenzyl) phthalate (DEHP) and dioctyl phthalate were analysed in raw and treated wastewater as well as in surface runoff samples from traffic roads. All six investigated phthalates have been detected in all raw sewage samples, in nearly all wastewater treatment plant (WWTP) effluent samples and in all road runoff samples, with DEHP being the most abundant compound. DEHP inflow concentrations ranged 3.4– 34 lg L 1 and effluent concentrations 0.083–6.6 lg L 1. In two WWTPs the fate of the phthalates was assessed by performing mass balances. Overall removal efficiencies of approx 95% were calculated. Removal is attributed to biotransformation and adsorption and the relevance of the removal via adsorption to sludge increased with increasing molecular weight and increasing lipophilic character of the compound. Except DEHP phthalate concentrations were higher in treated effluent samples than in road runoff. The environmental quality standard (EQS) for DEHP in surface waters is exceeded only in a few effluent samples, whereas nearly all road runoff samples were higher than the EQS. An assessment based on pure concentrations is not feasible and a mass balance based approach is required. Nevertheless the observations highlight the relevance of stormwater emissions and direct emissions from separated sewer systems to surface waters in relation to emissions from WWTPs and the necessity to consider all potential influences in the assessment of the status of surface water bodies with reference to xenobiotics. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Phthalates are esters of the phthalic acid and are a group of chemicals of high environmental relevance due to their production rates and ecotoxicological potential. Phthalates are among the most important industrial chemicals and several representatives are high production volume chemicals (ESIS, 2009). Worldwide annual production of phthalates amounts to more than 4 Mt, from which approx 1 Mt is produced in Europe (Peijnenburg and Struijs, 2006). The most important representative was bis(2-ethylhexyl) phthalate (DEHP) (AgPU, 2006; Cardogan, 2007; EU-RAR, 2008). Due to its classification as toxic to reproduction, the corresponding labelling (skull and crossbones) and several restrictions on marketing and use (2003/36/EC, 2004/93/EC, 2005/84/EC) DEHP is replaced with other phthalate plasticizers as di-isodecyl phthalate (DIDP) and di-isononyl phthalate (DINP). With the total amount of plasticizer consumption remaining unchanged in Europe, the consumption of DEHP dropped from 42% in 1999 to 21% in 2006, whereas the share of DIDP and DINP increased from 35% to 60% * Corresponding author. Tel.: +43 1 31304 5612; fax: +43 1 31304 5622. E-mail address: [email protected] (M. Clara). 0045-6535/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2009.12.052
within the same time period (AgPU, 2006; Cardogan, 2007). Phthalates are chemically stable, colour-, odour- and flavourless, liquids over a wide temperature range and hardly soluble in water. The main use of phthalates is as additives in plastics, especially in plasticized polyvinyl chloride (PVC) as well as in the production of paints and varnishes, adhesives, lubricants and cosmetics (EURAR, 2008). Various phthalates are classified as toxic to reproduction and they are known to affect reproduction in animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations (Call et al., 2001a,b; EU-RAR, 2004, 2007, 2008; Oehlmann et al., 2009). Oehlmann et al. (2009) identified molluscs, crustaceans and amphibians to be especially sensitive to phthalates and biological effects occur at environmentally relevant exposures in the low ng L 1–lg L 1 range. As phthalates are not chemically bound to the polymeric matrix in soft PVC they can enter the environment by losses during manufacturing processes and by leaching or evaporating from final products. Once released to the environment they tend to adsorb on particles. Phthalates have been detected in rainwater (Clark et al., 2003; Teil et al., 2006), surface water (Fromme et al., 2002; Clark et al., 2003; EU-RAR, 2004, 2007, 2008; Yuwatini et al.,
M. Clara et al. / Chemosphere 78 (2010) 1078–1084 Table 1 Characterisation of the six investigated phthalates (data taken from EU-RAR, 2004, 2007, 2008; Syracuse model http://www.srcinc.com/what-we-do/databaseforms.aspx?id = 386; KOC values calculated with EPISUITE v3.12). Substance
CAS
Dimethyl phthalate
DMP
Diethyl phthalate
DEP
Dibutyl phthalate
DBP
Butylbenzyl phthalate Bis(2-ethylbenzyl) phthalate Dioctyl phthalate
BBP DEHP DOP
13111-3 8466-2 8474-2 8568-7 11781-7 11784-0
MW
SW (mg L
1
)
log KOW (–)
log KOC (L kg 1)
194.19
4000
1.60
1.569
222.24
1080
2.42
2.101
278.34
10
4.57
3.802
312.37
2.8
4.84
4.021
390.57
0.003
7.5
5.217
390.57
0.022
8.10
5.291
SW: solubility in water; KOW: octanol–water partition constant; KOC: organic carbon–water partition coefficient.
2006; Gasperi et al., 2009), treated and untreated wastewater (Fromme et al., 2002; Fauser et al., 2003; Marttinen et al., 2003; EU-RAR, 2004, 2007, 2008; Roslev et al., 2007; Tan et al., 2007; Dargnat et al., 2009), sewage sludge (Fromme et al., 2002; Marttinen et al., 2003; EU-RAR, 2004, 2007, 2008), sediments (Fromme et al., 2002; Yuwatini et al., 2006; EU-RAR, 2007, 2008; Björklund et al., 2009) and in stormwater (Björklund et al., 2009). In the European Union DEHP is defined as priority substance in the Water Framework Directive (2000/60/EC) with the aim to reduce uses and emissions of DEHP to surface waters. Directive 2008/105/EC defines a limit value for surface waters for DEHP of 1.3 lg L 1. The present article focuses on the occurrence of six phthalate esters in untreated and treated wastewater, in sewage sludge as well as in the runoff from streets. By performing a mass balance the fate of the studied phthalates during wastewater treatment is assessed. The investigated substances and relevant physical– chemical properties are summarised in Table 1. 2. Materials and methods 2.1. Chemicals and reagents Phthalate esters were purchased from Supelco, isotope labeled phthalates from CDN Isotopes Inc. (Dr. Ehrensdorfer, Augsburg, Germany). Solvents of residue grade were from LGC Standards (Wesel, Germany), whereas other reagents were purchased from VWR (Vienna, Austria). 2.2. Sample preparation 2.2.1. Sewage sludge After spiking 1 g of sewage sludge sample with deuterated phthalates 60 mL ethyl acetate were added. The deuterated phthalate standard included all six investigated phthalates. The extraction was carried out on an ultrasonic bath for 30 min. The extract was applied to an aluminium oxide clean up column and afterwards concentrated under a gentle stream of nitrogen to a final volume of 1 mL. 2.2.2. Waste water and road/surface runoff Two hundred millilitre of sample were spiked with deuterated phthalates and sodium chloride was added. The samples were extracted five times with 4 mL of n-hexane. For waste water samples occasionally dichloromethane was used instead of n-hexane. The
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combined extracts were concentrated under a gentle stream of nitrogen to 0.2 mL. 2.3. Chemical analysis Laboratory reagent blanks (extracted and prepared as for samples) and instrumental blanks were analysed with each batch of samples to check and correct for possible contamination and interferences. Ten percent of the samples were repeat determinations, meaning that the whole sample preparation and analysis has been done twice. Prior to GC–MS analysis an injection standard consisting in dicyclohexylphthalate-D4, methylpamitate and di-n-propylphthalateD4 was added to all samples (40 ng to water samples, 100 ng to sludge samples). The GC–MS analysis (Thermoquest Trace GC/MS System) was carried out on a DB-5 column (60 m 0.25 mm inner diameter, 0.25 lm film thickness) using the selected ion monitoring mode. Following temperature programme was employed: temperature increase from 60 to 185 °C with a temperature gradient of 15 °C min 1, holding 185 °C for 1 min, further temperature increase from 185 to 310 °C with a temperature gradient of 6 °C min 1 and held at 310 °C for 5 min. Injection temperature and transfer line temperature were set to 330 °C, source temperature to 255 °C. Limits of quantification (LOQ) as well as limits of detection (LOD) were dependent on sample matrix and volume, blank contamination as well as recovery ratios of the added deuterated surrogate standard. Basic validation was performed by using the statistical software package SQS in accordance with the German standard method DIN 32645 (DIN 32645, 1996). LOD and LOQ were calculated by multiplying those basic validation values with the enrichment factors and the recoveries of the analytes. LOQ and LOD of the investigated wastewater, sludge and road/surface runoff samples are provided in the respective result tables. Beside DBP recovery ratios of the deuterated surrogate standards ranged from 47% up to 125% (for DBP a maximum recovery ratio of 145% was observed) in the water samples and from 77% up to 108% in the sewage sludge samples. Measurements below the LOQ have been considered with the mean of LOD and LOQ and analytical results below the LOD were set equal to zero. 2.4. Sampling and sampling sites 2.4.1. Wastewater treatment plants Seventeen municipal wastewater treatment plants (WWTPs) of different treatment capacities (ranging from 2000 to 4 000 000 population equivalents, pe) and applying different treatment technologies (trickling filters, activated sludge) were sampled. All investigated WWTPs remove carbon and phosphorous and are nitrifying WWTPs. With exception of one plant all sampled WWTPs are also removing nitrogen by applying nitrification–denitrification processes. From 15 of those WWTPs daily composite influent and effluent samples were taken once, whereas from two WWTPs daily composite samples were taken over a period of 2 weeks. Based on these samples 2-d composite samples were mixed in the laboratory and subjected to chemical analysis. For these two WWTPs mass balances were calculated in order to illustrate the fate of the six phthalates during wastewater treatment. Beside the six phthalates also conventional wastewater parameters as COD, total nitrogen and total phosphorus (TP) were determined in all samples. These parameters served to assess general operation and performance of the sampled WWTPs and mass balances of TP and COD served as basis and plausibility control for the phthalates mass balances.
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2.4.2. Road/surface runoff At two stations along traffic roads samples from the surface runoff were taken. At one sampling station surface runoff from a motorway is collected, whereas the second sampling point was situated beside a street in a suburban area. From the motorway runoff grab samples were collected and from the suburban street flow proportional composite samples were taken. The yearly average daily traffic (ADT) on the motorway amounts to approx 42 000 vehicles d 1 of which ca 43% heavy traffic. The drained area at the suburban street includes vehicle and bicycle lanes as well as sidewalks. The ADT amounts to approx 24 000 vehicles d 1 of which ca 5% is attributed to heavy traffic. The sampled road section is exposed to wind (bridge) and characterised by stop and go traffic due to a traffic light. Both sampling stations were sampled four times from October to December 2008. 3. Results and discussion 3.1. Occurrence of phthalate esters 3.1.1. Wastewater Detection frequency as well as a summary of the measured concentrations of the six analysed phthalates in untreated and treated sewage in 15 WWTPs is provided in Table 2. In the influent DEP, BBP and DEHP were found in all samples, whereas detection frequencies for DMP, DBP and DOP amounted to 87%, 53% and 80%, respectively. In the effluent only BBP and DEHP were detected in all samples, whereas detection frequencies for DMP, DEP, DBP and DOP amounted to 60%, 80%, 53% and 7%, respectively. Beside DOP the detection frequencies in influent and effluent are comparable, but the concentrations measured in the influent are notably higher than those in the effluent, highlighting the removal capacity of municipal WWTPs for phthalates. In the influent as well as in the effluent the concentrations of the various phthalates varied strongly. The most abundant compound in the influent was DEHP (3.4–34 ng L 1), followed by DEP (0.77–9.2 ng L 1) and DBP (n.d. 8.7 ng L 1). The remaining phthalates BBP, DMP and DOP were of minor importance with concentrations around or below 1 lg L 1. In the effluent notably lower concentrations than in the influent were observed, but the distribution more or less remained unchanged. Also in the effluent DEHP
was the most abundant compound with concentrations ranging 0.083 up to 6.6 ng L 1, followed by DBP (n.d. 2.4 ng L 1) and BBP (0.088–1.4 ng L 1). DMP (n.d. 0.19) is of minor importance and DOP was detected only in one of the analysed effluent samples. Comparable distributions and comparable concentrations in influent and effluent were reported by Gasperi et al. (2008) and Dargnat et al. (2009). Also Marttinen et al. (2003) and Roslev et al. (2007) observed a comparable distribution but slightly higher concentrations. Higher effluent concentrations are reported also by Fromme et al. (2002) with DEHP ranging 1.74–182 lg L 1 and DBP ranging 0.2–10.4 lg L 1 in treated sewage and also by Marttinen et al. (2003) observing 6 lg L 1 of DEHP. Those higher concentrations in former studies may at least be partially explained by the fact, that DEHP is continuously replaced by other phthalate plasticizers. Specific pe loads in the influents were determined and referred to the industrial wastewater proportion. The industrial influence in the drainage area is calculated by determining the COD mass flux deriving from inhabitants with a specific COD load of 120 g COD pe 1 d 1 and referring this COD load to the total measured COD load in the sampled WWTPs. The difference is attributed to commerce and industry. In order to account uncertainties three categories are defined. Category 1 is a domestic area with influence of industry below 25%, category 2 has a mixed drainage area with industrial/commercial influences between 25% and 75% and category 3 is dominated by industry (more than 75% of the COD flux in the influent attributed to industry). Results for DEP and DEHP as the dominant phthalates are shown in Fig. 1. The specific pe discharges vary within a wide range, but highest values are calculated for drainage areas dominated by households and low industrial/commercial influences. This observation corresponds to the results reported by Vethaak et al. (2005) observing the highest phthalate concentrations in wastewaters from residential areas. 3.1.2. Road/surface runoff (stormwater) The measured concentrations of the analysed phthalate esters in the road runoff samples varied strongly (see Table 3). The most important compound in the runoff from traffic roads is DEHP with concentrations ranging 0.45–24 lg L 1, showing also the highest relative composition of total phthalate concentrations in all samples. In these samples also DINP and DIDP were analysed. Both
Table 2 occurrence of the six analysed phthalates in raw and treated wastewater (n = 15). Substance
Influent LOQ (lg L
a
1
)
Effluent LOD (lg L
1
)
n < LOD (–)
n > LOD (–)
DFa (%)
DMP
0.26–1.5
0.073–0.74
2
13
87
DEP
0.41–0.75
0.12–0.21
0
15
100
DBP
0.29–14
0.083–6.8
7
8
53
BBP
0.25–1
0.066–0.28
0
15
100
DEHP
0.23–0.28
0.061–0.075
0
15
100
DOP
0.48–0.95
0.13–0.26
3
12
80
DF: detection frequency; n.d.: not detected.
DFa (%)
Mean (min–max) (ng L 1)
Median (ng L 1)
9
60
0.062 (n.d.–0.19)
0.090
3
12
80
0.20 (n.d.–1.1)
0.15
0.044–4.8
7
8
53
0.54 (n.d.–2.4)
0.34
0.13–0.56
0.033–0.15
0
15
100
0.31
18
0.12–0.26
0.032–0.07
0
15
100
0.54
0.24–0.51
0.067–0.14
14
1
7
0.36 (0.088– 1.4) 1.6 (0.083– 6.6) 0.017 (n.d.–0.26)
Mean (min– max) (ng L 1)
Median (ng L 1)
LOQ (lg L
0.95 (n.d.– 2.4) 4.1 (0.77– 9.2) 2.2 (n.d.– 8.7) 0.95 (0.31– 3.2) 18 (3.4– 34) 0.49 (n.d.– 1.1)
0.88
0.14–0.81
0.04–0.4
6
3.9
0.23–0.4
0.065–0.11
0.76
0.15–9.6
0.9
1
)
LOD (lg L
1
)
n < LOD (–)
n > LOD (–)
0.50
n.d.
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DINP was detected in all samples and the concentrations are comparable to those observed for DEHP varying from 0.22 up to 23 lg L 1. The other investigated phthalates beside DEHP and DINP are of minor importance, with concentrations all below 0.5 lg L 1. In order to make the various phthalates comparable, the measured concentrations were normalised to M. The relevance of the various phthalates in the investigated samples due to their relative proportions (average ± standard deviation) correspond to DINP (54 ± 15%), DEHP (38 ± 14%), DIDP (4.5 ± 7.4), DEP (1.5 ± 1.5%), DBP (0.9 ± 1.0%), DOP (0.6 ± 0.5%), DMP (0.4 ± 0.4%) and BBP (0.2 ± 0.2%). Hence DINP and DEHP contribute to approx 92 ± 21% of the overall phthalate emission. The detection frequencies for the phthalates were highest for DEHP, DEP and DINP (100%), followed by DOP (88%), DMP (75%), BBP and DBP (63%) as well as DIDP (38%). For all investigated phthalates a strong correlation to the total suspended solids concentrations in the samples is observed, confirming that phthalates in the runoff from traffic roads are to a large extend associated to particles. Thus is in line with the physical–chemical properties summarised in Table 1 showing high partitioning coefficients for the higher molecular phthalates. Only few data on the occurrence of phthalates in stormwater are available. Björklund et al. (2009) detected all phthalates in one or more stormwater samples, but significant variations in the concentrations occurred. Highest concentrations were observed for DINP (up to 85 lg L 1), DIDP (up to 17 lg L 1) and DEHP (up to 5.0 lg L 1) whereas the other five phthalic esters were detected in concentrations below 0.5 lg L 1 (Björklund et al., 2009). Beside the fact, that Björklund et al. (2009) document notably higher concentrations for DINP and DIDP the measured concentrations vary within a comparable range.
14
1a-DEHP 12
specific load [mg pe-1 d-1]
10 8 6 4 2 0 3.0
1b-DEP specific load [mg pe-1 d-1]
2.5 2.0 1.5 1.0 0.5 0.0
Category 1 1
Category 2
Category 3
1
Fig. 1. Specific pe loads (mg pe d ) for (a) DEHP and (b) DEP for the sampled wastewater treatment plants in dependence on the respective industrial influence.
compounds were detected in notable concentrations. DIDP was only found in a few samples but in concentrations up to 9.9 lg L 1.
Table 3 Measured concentrations of the analysed phthalic esters (lg L 1
)
DMP (lg L
1
)
1
) and total suspended solids (TSS) (mg L
DEP (lg L
1
)
DBP (lg L
1
)
BBP (lg L
1
)
1
) in road runoff samples.
DEHP (lg L
1
)
DOP (lg L
1
)
DINP (lg L
1
)
DIDP (lg L
Sampling site
TSS (mg L
LOQ LOD
– –
0.01 0.005
0.02 0.01
0.05 0.025
0.01 0.005
0.2 0.1
0.01 0.005
0.01 0.005
0.02 0.01
Motorway Sampling 1 Sampling 2 Sampling 3 Sampling 4
82 22 26 430
n.d. <0.01 n.d. 0.1
<0.02 0.051 0.021 0.27
n.d. n.d. n.d. 0.079
n.d. n.d. n.d. 0.33
5.3 2.4 0.45 24
0.061 0.01 n.d. 0.53
7.9 2.2 0.22 23
n.d. n.d. n.d. 9.9
Suburban area Sampling 1 Sampling 2 Sampling 3 Sampling 4
18 27 190 75
0.023 0.042 0.079 0.049
0.035 0.048 0.16 0.13
0.13 0.12 0.27 0.2
0.027 0.014 0.082 0.039
2.3 1.4 8.5 5.6
0.05 0.019 0.17 0.37
6.9 4.8 23 12
n.d. n.d. 0.53 4.8
1
)
n.d.: not detected.
Table 4 Measured phthalic esters concentrations in untreated and treated wastewater (lg L Wastewater LOQ (lg L
1
)
LOD (lg L
DMP DEP
0.1 0.1
0.05 0.05
DBP BBP DEHP DOP
0.1 0.1 0.2 0.1
0.05 0.05 0.1 0.05
n.d.: not detected.
1
) and in the sludge samples (lg kg
1
dry weight) of the two mass balance subjected WWTPs.
Sludge WWTP 1
WWTP 2
1
)
Influent (lg L 1)
Effluent (lg L 1)
0.26–0.41 n.d. 1.2–2 n.d.– < 0.1 <0.1–0.47 n.d. n.d.–0.11 n.d. 4.4–8.8 <0.2–0.28 n.d. n.d.
Influent (lg L 1)
Effluent (lg L 1)
LOQ (lg kg
1
)
LOD (lg kg
WWTP 1
WWTP 2
1
)
Primary sludge (lg kg 1)
Excess sludge (lg kg 1)
Primary sludge (lg kg 1)
Excess sludge (lg kg 1)
0.43–0.81 n.d. 2.2–2.7 n.d.
40 40
20 20
74 85
89 85
<40 61
56 70
n.d. 44
n.d. 55
n.d. 130
n.d. <40
0.15–0.41 0.11–0.26 4.1–13 n.d.– < 0.1
100 100 800 40
50 50 400 20
270 140 24 000 130
290 140 25 000 180
810 120 22 000 58
1200 130 27 000 96
310 180 20 000 140
850 380 27 000 260
– 250 27 000 89
640 200 29 000 120
n.d. n.d. <0.2–1.3 n.d.
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3.1.3. Fate of phthalates during wastewater treatment Two WWTPs have been investigated in detail in order to assess the fate of the six phthalates during wastewater treatment. Beside influent and effluent samples also primary and excess sludge were analysed twice for the six phthalates. Measured phthalate concentrations in untreated and treated wastewater as well as in sewage sludges are shown in Table 4. Both WWTPs operate a primary clarification followed by an activated sludge treatment. In WWTP 1 the excess sludge is pumped to the primary clarification where it is removed from the system together with the primary sludge. Totally approx 2350 kg sludge (in terms of TSS) are removed daily. In WWTP 2 primary sludge is removed from primary clarification (approx 5540 kg TSS d 1) whereas the excess sludge (approx 6845 kg TSS d 1) is removed from the sludge recycle. Mean daily inflow amounted to 7780 m3 d 1 in WWTP 1 and to 69 010 m3 d 1 in WWTP 2. Both WWTPs are removing nitrogen by nitrification/denitrification and operating sludge retention times of approx 17 d (WWTP 1) and 12 d (WWTP 2). Results of TP and phthalates mass balances for the two WWTPs are summarised in Fig. 2. As TP is not degraded, the fluxes in effluent and sludge have to be equal to the inflow flux. Therefore TP mass balance is an indicator for the quality of the balanced system. For both WWTPs sound results are obtained with WWTP 2 performing slightly better than WWTP 1. Beside BBP for both WWTPs a comparable distribution and behaviour of the investigated phthalates is observed. The overall removal via adsorption to sludge and biotransformation is higher than 95% for all compounds. Comparable overall removal for DEHP is reported also by Fauser et al. (2003) and Marttinen et al. (2003) and in EU-RAR (2008). Slightly lower overall removal for DEHP is observed by Tan et al. (2007) and Dargnat et al. (2009) whereas total efficiencies obtained for the other investigated phthalates are comparable.
Biotransformation Effluent Sludge
2a - WWTP 1
100 80 60 40
not applicable
specific flux [%] (referred to influent)
120
20 0
2b-WWTP 2
100 80 60 40
not applicable
specific flux [%] (referred to influent)
120
20 0 TP
DMP
DEP
DBP
BBP DEHP DOP
Substance Fig. 2. Mass balance results for the investigated phthalates in two WWTPs ((a) WWTP 1 and (b) WWTP 2).
It has to be considered, that most of the six phthalates were not detected in the effluent of the two WWTPs. In WWTP 1 only DEHP and in WWTP 2 DEHP and DEP were detected in the effluent samples. Setting analytical results below the LOD equal to zero the overall removal as well as the removal attributed to biotransformation are slightly overestimated. Nevertheless the results provide an estimate of the relevance of the two removal pathways. The importance of adsorption and the removal pathway via sludge increases with increasing molecular weight and with increasing lipophilic character of the substance (compare with log KOW values summarised in Table 1). This increasing relevance of adsorption with increasing log KOW is seen in both investigated WWTPs. In WWTP 1 (WWTP 2) the proportional mass fraction removed with the sludge amounts to 3.4% (0%) for DMP, 1.0% (0.7%) for DEP, 76% (64%) for DBP, 21% (74%) for BBP and 78% (81%) for DEHP. Comparable results for the overall removal (91%) for BBP and DBP are reported in the respective risk assessment reports (EU-RAR, 2004, 2007) but slightly higher removals due to biodegradation/biotransformation (50% and 58%) and slightly lower removal via adsorption (42% and 33%) to sludge is reported. A comparable result for DEHP is documented by Marttinen et al. (2003) and EU-RAR (2008). Marttinen et al. (2003) calculated an overall removal efficiency of 97%. Fourteen percent of the DEHP load in the influent is removed by biodegradation/biotransformation and 68% are removed by adsorption to primary and excess sludge. Modelling the removal of DEHP in a WWTP by applying the European Union System for the evaluation of substances, an overall removal efficiency of 93% is obtained, of which 15% are attributed to biodegradation/biotransformation and 78% to adsorption to sludge (EU-RAR, 2008). Fauser et al. (2003) observed higher impact of biodegradation on phthalates removal in WWTPs. Removal efficiencies of 60–70% due to biodegradation/ biotransformation were calculated whereas 20–35% are attributed to removal by sorption to primary and secondary sludge (Fauser et al., 2003). With the calculated removals and considering biomass concentrations in the reactors apparent degradation rate constants kbio were calculated according to the methodology described in Clara et al. (2005). For the calculation of kbio effluent concentrations were set equal to the LOQ as only DEHP was detected in the effluent samples, These estimates for kbio (L g 1 TSS d 1) were calculated with >4.3 and >5.2 for DMP, with >19 and 26 for DEP, with >0.50 and >0.98 for DBP, with >1.2 and >0.26 for BBP and with 1.6 and 4.1 for DEHP in WWTP 1 and WWTP 2, respectively. In the respective risk assessment reports (EU-RAR, 2004, 2007, 2008) DBP, BBP and DEHP are classified as ready biodegradable during wastewater treatment and a degradation rate constant of 1 h 1 is applied. For DBP and BBP notably lower kbio values were observed in the two WWTPs. A possible explanation is the substrate limitation in the biological reactor as all measured effluent concentrations were below the LOD, whereas the risk assessments rely on standardised tests applying high substrate concentrations in order to avoid substrate limitation. Only DEHP was quantified in the effluent. Considering usual TSS concentrations of 3–4 g L 1 in the biological reactor kbio ranges from 0.2 (WWTP 1) to 0.7 h 1 (WWTP 2). Phthalates also strongly tend to accumulate on sludge and the adsorbed mass seems not to be available for biodegradation anymore. Nevertheless the results highlight the high removal potential of biological wastewater treatment systems for phthalate removal from wastewater. Due to the limitations (effluent concentrations below LOQ) the provided values for kbio only can be rough estimates underrating the biodegradation potential but nevertheless they should be useful for a first assessment. In WWTP 2 DEHP was detected in the excess sludge as well as in the effluent. The aeration tank can be regarded as a completely mixed reactor with the dissolved effluent concentration corre-
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a
WWTP effluents Road runoff
10
1
0.1
0.01
100
relative concentration [-] c / cEQS
Concentration [µg L -1]
100
DEHP
DEP
DBP
10
1
1
0.1
BBP DEHP DOP
Fig. 3. Comparison (a) of the phthalate ester concentrations (lg L the EQS for DEHP for treated wastewater and road runoff.
1
100
10
0.1
0.01
DMP
b
0.01
WWTP effluent
Road runoff
) observed in treated wastewater and in road runoff and (b) relative DEHP concentrations (–) referred to
sponding to the dissolved concentration in the reactor. Based on this assumption it is possible to calculate an estimate for the solid–liquid distribution coefficient Kd from the measured values. Considering a mean effluent concentration of <0.20 lg L 1 and an average sludge concentration of 28 000 lg kg 1 an apparent Kd value of >140 000 L kg 1 (log Kd 5.15) is calculated. This calculated apparent Kd value is notably higher than those provided by Fauser et al. (2003) and applied in the risk assessment (EU-RAR, 2008) but it is within the range given in EU-RAR (2008). 3.1.4. Impact of emissions to surface water quality Directive 2008/105/EC defines an environmental quality standard (EQS) in surface waters for DEHP only and sets it equal to 1.3 lg L 1. In Fig. 3 the measured concentrations (mean, minimum and maximum) in the effluents of the investigated WWTPs (n = 15) as well as in the road runoff samples (n = 8) are shown. With exception of DEHP concentrations were notably higher in WWTP effluents than in road runoff. For DEHP the measured concentrations in WWTP effluents and in the road runoff samples are related to the EQS for DEHP (see Fig. 3). Whereas only in a few effluent samples DEHP concentrations exceeding the EQS were detected, in nearly all road runoff samples the ratio of the DEHP concentration in the sample and the EQS was higher than 1. This observation highlights the potential impact of surface water runoff emissions to surface waters. Obviously a pure comparison of concentration is not feasible and a more detailed assessment based on emitted fluxes and on mass balance considerations has to be performed. Nevertheless the results indicate that stormwater overflows as well as surface runoff to surface waters might have considerable impact on surface water quality. Especially considering the fact, that during the last decade a trend towards separate sewer systems was observed and only the sewage is treated in a WWTP whereas the surface runoff often is emitted to surface waters without any treatment. 4. Conclusions All investigated phthalates were detected in raw and treated sewage as well as in the runoff from roads. In the WWTPs a notable removal of up to 95% is observed which is attributed to biodegradation and adsorption to sludge. But even considering these removal efficiencies the emitted concentrations may exceed actual surface water quality standards. Especially in domestic areas and for WWTPs emitting to small receiving waters the emissions may be of relevance for those receiving water bodies. Beside emissions from WWTP also stormwater emissions as well as emissions from separated sewer systems may have a considerable impact on surface water quality. In order to make an in depth assessment of surface waters status with reference to xeno-
biotics on a catchment scale, further research is required to assess the relevance of other emission pathways than WWTPs. In this context one of the major difficulties is the assessment of frequency and duration of stormwater events and the collection of representative samples. Acknowledgement Parts of the work presented were financed by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management in cooperation with the nine Austrian Federal States. References AgPU, 2006. Plasticizers Market Data – Compiled by the Arbeitsgemeinschaft PVC und Umwelt e.V.. Björklund, K., Cousins, A.P., Strömvall, A.-M., Malmqvist, P.-A., 2009. Phthalates and nonylphenols in urban runoff: occurrence, distribution and area emission factors. Sci. Total Environ. 407, 4665–4672. Call, D.J., Cox, D.A., Geiger, D.L., Genisot, K.I., Markee, T.P., Brooke, L.T., Polkinghorne, C.N., VandeVenter, F.A., Gorsuch, J.W., Robillard, K.A., Parkerton, T.F., Reiley, M.C., Ankley, G.T., Mount, D.R., 2001a. An assessment of the toxicity of phthalate esters to freshwater benthos: 1. Aqueous exposures. Environ. Toxicol. Chem. 20, 1798–1804. Call, D.J., Cox, D.A., Geiger, D.L., Genisot, K.I., Markee, T.P., Brooke, L.T., Polkinghorne, C.N., VandeVenter, F.A., Gorsuch, J.W., Robillard, K.A., Parkerton, T.F., Reiley, M.C., Ankley, G.T., Mount, D.R., 2001b. An assessment of the toxicity of phthalate esters to freshwater benthos: 1. Sediment exposures. Environ. Toxicol. Chem. 20, 1805–1815. Cardogan, D., 2007. The Current Plasticizer Situation in Europe. Presentation at Phthalates and New Plasticisers for PVC Conference. Copenhagen, Denmark, September 2007. . Clara, M., Kreuzinger, N., Strenn, B., Gans, O., Kroiss, H., 2005. The solids retention time – a suitable design parameter to evaluate the capacity of wastewater treatment plants to remove micropollutants. Water Res. 39, 97–106. Clark, K., Cousins, I.T., Mackay, D., Yamada, K., 2003. Observed concentrations in the environment. In: Staples, C.A. (Ed.), Phthalate Esters – The Handbook of Environmental Chemistry Part Q, vol. 3. Springer-Verlag, Berlin-Heidelberg, Germany, pp. 125–177. Dargnat, C., Teil, M.J., Chevreuil, M., Blanchard, M., 2009. Phthalate removal throughout wastewater treatment plant: case study of Marne Aval station (France). Sci. Total Environ. 407, 1235–1244. ESIS, 2009. European Chemical Substances Information System. . EU-RAR, 2007. European Union Risk Assessment Report on Benzyl Butyl Phthalate (BBP). Institute of Health and Consumer Protection (IHCP), European Chemicals Bureau, 3rd Priority List, vol. 76. . EU-RAR, 2008. European Union Risk Assessment Report on Bis(2-ethylhexyl) Phthalate (DEHP). Institute of Health and Consumer Protection (IHCP), European Chemicals Bureau, 2nd Priority List, vol. 80.
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ec.europa.eu/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/REPORT/ dehpreport042.pdf>. Fauser, P., Vikelsøe, J., Sørensen, P.B., Carlsen, L., 2003. Phthalates, nonylphenols and LAS in an alternately operated wastewater treatment plant – fate modeling based on measured concentrations in wastewater and sludge. Water Res. 37, 1288–1295. Fromme, H., Küchler, T., Otto, T., Pilz, K., Müller, J., Wenzel, A., 2002. Occurrence of phthalates and bisphenol A and F in the environment. Water Res. 36, 1429–1438. Gasperi, J., Garnaud, S., Rocher, V., Moilleron, R., 2008. Priority pollutants in wastewater and combined sewer overflow. Sci. Total Environ. 407, 263–272. Gasperi, J., Garnaud, S., Rocher, V., Moilleron, R., 2009. Priority pollutants in surface waters and settleable particles within a densely urbanized area: case study of Paris (France). Sci. Total Environ. 407, 2900–2908. Marttinen, S.K., Kettunen, R.H., Sormunen, K.M., Rintala, J.K., 2003. Removal of bis(2ethylhexyl) phthalate at a sewage treatment plant. Water Res. 37, 1385–1393. Oehlmann, J., Schulte-Oehlmann, U., Kloas, W., Jagnytsch, O., Lutz, I., Kusk, K.O., Wollenberger, L., Santos, E.M., Paull, G.C., Van Look, K.J., Tyler, C.R., 2009. A critical analysis of the biological impacts of plasticizers on wildlife. Philos. Trans. R. Soc. B 364, 2047–2062. DIN 32645, 1996. Chemical Analysis – Decision Limit, Detection Limit and Determination Limit – Estimation in Case of Repeatability, Terms, Methods,
Evaluation. Deutsches Institut für Normung e.V., German Standard Method DIN 32 645. Beuth Verlag, Berlin, Wien, Zürich. Peijnenburg, W.J.G.M., Struijs, J., 2006. Occurrence of phthalate esters in the environment of the Netherlands. Ecotox. Environ. Safe. 63, 204–215. Roslev, P., Vorkamp, K., Aarup, J., Frederiksen, K., Nielsen, P.H., 2007. Degradation of phthalate esters in an activated sludge wastewater treatment plant. Water Res. 41, 969–976. Tan, B.L.L., Hawker, D.W., Müller, J.F., Leush, F.D.L., Tremblay, L.A., Chapman, H.F., 2007. Modelling the fate of selected endocrine disruptors in a municipal wastewater treatment plant in South East Queensland, Australia. Chemosphere 69, 644–654. Teil, M.J., Blanchard, M., Chevreuil, M., 2006. Atmospheric fate of phthalate esters in an urban area (Paris-France). Sci. Total Environ. 354, 212–223. Vethaak, A.D., Lahr, J., Schrap, S.M., Belfroid, A.G., Rijs, G.B.J., Gerritsen, A., de Boer, J., Bulder, A.S., Grinwis, G.C.M., Kuiper, R.V., Legler, J., Murk, T.A.J., Peijnenburg, W., Verhaar, H.J.M., de Voogt, P., 2005. An integrated assessment of oestrogenic contamination and biological effects in the aquatic environment of the Netherlands. Chemosphere 59, 511–524. Yuwatini, E., Hata, N., Taguchi, S., 2006. Behaviour of di(2-ethylhexyl) phthalate discharged from domestic waste water into aquatic environment. J. Environ. Monitor. 8, 191–196.
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Occurrence of phthalates in surface runoff, untreated and treated wastewater and fate during wastewater treatment M. Clara a,*, G. Windhofer a, W. Hartl a, K. Braun a, M. Simon a, O. Gans a, C. Scheffknecht b, A. Chovanec a a b
Umweltbundesamt GmbH, Spittelauer Lände 5, 1090 Vienna, Austria Environmental Institute of the State of Vorarlberg, Montfortstraße 4, 6901 Bregenz, Austria
a r t i c l e
i n f o
Article history: Received 9 October 2009 Received in revised form 21 December 2009 Accepted 22 December 2009 Available online 22 January 2010 Keywords: Phthalates Surface waters Surface runoff Wastewater Sewage sludge Wastewater treatment
a b s t r a c t Dimethyl phthalate, diethyl phthalate, dibuthyl phthalate, butylbenzyl phthalate, bis(2-ethylbenzyl) phthalate (DEHP) and dioctyl phthalate were analysed in raw and treated wastewater as well as in surface runoff samples from traffic roads. All six investigated phthalates have been detected in all raw sewage samples, in nearly all wastewater treatment plant (WWTP) effluent samples and in all road runoff samples, with DEHP being the most abundant compound. DEHP inflow concentrations ranged 3.4– 34 lg L 1 and effluent concentrations 0.083–6.6 lg L 1. In two WWTPs the fate of the phthalates was assessed by performing mass balances. Overall removal efficiencies of approx 95% were calculated. Removal is attributed to biotransformation and adsorption and the relevance of the removal via adsorption to sludge increased with increasing molecular weight and increasing lipophilic character of the compound. Except DEHP phthalate concentrations were higher in treated effluent samples than in road runoff. The environmental quality standard (EQS) for DEHP in surface waters is exceeded only in a few effluent samples, whereas nearly all road runoff samples were higher than the EQS. An assessment based on pure concentrations is not feasible and a mass balance based approach is required. Nevertheless the observations highlight the relevance of stormwater emissions and direct emissions from separated sewer systems to surface waters in relation to emissions from WWTPs and the necessity to consider all potential influences in the assessment of the status of surface water bodies with reference to xenobiotics. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Phthalates are esters of the phthalic acid and are a group of chemicals of high environmental relevance due to their production rates and ecotoxicological potential. Phthalates are among the most important industrial chemicals and several representatives are high production volume chemicals (ESIS, 2009). Worldwide annual production of phthalates amounts to more than 4 Mt, from which approx 1 Mt is produced in Europe (Peijnenburg and Struijs, 2006). The most important representative was bis(2-ethylhexyl) phthalate (DEHP) (AgPU, 2006; Cardogan, 2007; EU-RAR, 2008). Due to its classification as toxic to reproduction, the corresponding labelling (skull and crossbones) and several restrictions on marketing and use (2003/36/EC, 2004/93/EC, 2005/84/EC) DEHP is replaced with other phthalate plasticizers as di-isodecyl phthalate (DIDP) and di-isononyl phthalate (DINP). With the total amount of plasticizer consumption remaining unchanged in Europe, the consumption of DEHP dropped from 42% in 1999 to 21% in 2006, whereas the share of DIDP and DINP increased from 35% to 60% * Corresponding author. Tel.: +43 1 31304 5612; fax: +43 1 31304 5622. E-mail address: [email protected] (M. Clara). 0045-6535/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2009.12.052
within the same time period (AgPU, 2006; Cardogan, 2007). Phthalates are chemically stable, colour-, odour- and flavourless, liquids over a wide temperature range and hardly soluble in water. The main use of phthalates is as additives in plastics, especially in plasticized polyvinyl chloride (PVC) as well as in the production of paints and varnishes, adhesives, lubricants and cosmetics (EURAR, 2008). Various phthalates are classified as toxic to reproduction and they are known to affect reproduction in animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations (Call et al., 2001a,b; EU-RAR, 2004, 2007, 2008; Oehlmann et al., 2009). Oehlmann et al. (2009) identified molluscs, crustaceans and amphibians to be especially sensitive to phthalates and biological effects occur at environmentally relevant exposures in the low ng L 1–lg L 1 range. As phthalates are not chemically bound to the polymeric matrix in soft PVC they can enter the environment by losses during manufacturing processes and by leaching or evaporating from final products. Once released to the environment they tend to adsorb on particles. Phthalates have been detected in rainwater (Clark et al., 2003; Teil et al., 2006), surface water (Fromme et al., 2002; Clark et al., 2003; EU-RAR, 2004, 2007, 2008; Yuwatini et al.,
M. Clara et al. / Chemosphere 78 (2010) 1078–1084 Table 1 Characterisation of the six investigated phthalates (data taken from EU-RAR, 2004, 2007, 2008; Syracuse model http://www.srcinc.com/what-we-do/databaseforms.aspx?id = 386; KOC values calculated with EPISUITE v3.12). Substance
CAS
Dimethyl phthalate
DMP
Diethyl phthalate
DEP
Dibutyl phthalate
DBP
Butylbenzyl phthalate Bis(2-ethylbenzyl) phthalate Dioctyl phthalate
BBP DEHP DOP
13111-3 8466-2 8474-2 8568-7 11781-7 11784-0
MW
SW (mg L
1
)
log KOW (–)
log KOC (L kg 1)
194.19
4000
1.60
1.569
222.24
1080
2.42
2.101
278.34
10
4.57
3.802
312.37
2.8
4.84
4.021
390.57
0.003
7.5
5.217
390.57
0.022
8.10
5.291
SW: solubility in water; KOW: octanol–water partition constant; KOC: organic carbon–water partition coefficient.
2006; Gasperi et al., 2009), treated and untreated wastewater (Fromme et al., 2002; Fauser et al., 2003; Marttinen et al., 2003; EU-RAR, 2004, 2007, 2008; Roslev et al., 2007; Tan et al., 2007; Dargnat et al., 2009), sewage sludge (Fromme et al., 2002; Marttinen et al., 2003; EU-RAR, 2004, 2007, 2008), sediments (Fromme et al., 2002; Yuwatini et al., 2006; EU-RAR, 2007, 2008; Björklund et al., 2009) and in stormwater (Björklund et al., 2009). In the European Union DEHP is defined as priority substance in the Water Framework Directive (2000/60/EC) with the aim to reduce uses and emissions of DEHP to surface waters. Directive 2008/105/EC defines a limit value for surface waters for DEHP of 1.3 lg L 1. The present article focuses on the occurrence of six phthalate esters in untreated and treated wastewater, in sewage sludge as well as in the runoff from streets. By performing a mass balance the fate of the studied phthalates during wastewater treatment is assessed. The investigated substances and relevant physical– chemical properties are summarised in Table 1. 2. Materials and methods 2.1. Chemicals and reagents Phthalate esters were purchased from Supelco, isotope labeled phthalates from CDN Isotopes Inc. (Dr. Ehrensdorfer, Augsburg, Germany). Solvents of residue grade were from LGC Standards (Wesel, Germany), whereas other reagents were purchased from VWR (Vienna, Austria). 2.2. Sample preparation 2.2.1. Sewage sludge After spiking 1 g of sewage sludge sample with deuterated phthalates 60 mL ethyl acetate were added. The deuterated phthalate standard included all six investigated phthalates. The extraction was carried out on an ultrasonic bath for 30 min. The extract was applied to an aluminium oxide clean up column and afterwards concentrated under a gentle stream of nitrogen to a final volume of 1 mL. 2.2.2. Waste water and road/surface runoff Two hundred millilitre of sample were spiked with deuterated phthalates and sodium chloride was added. The samples were extracted five times with 4 mL of n-hexane. For waste water samples occasionally dichloromethane was used instead of n-hexane. The
1079
combined extracts were concentrated under a gentle stream of nitrogen to 0.2 mL. 2.3. Chemical analysis Laboratory reagent blanks (extracted and prepared as for samples) and instrumental blanks were analysed with each batch of samples to check and correct for possible contamination and interferences. Ten percent of the samples were repeat determinations, meaning that the whole sample preparation and analysis has been done twice. Prior to GC–MS analysis an injection standard consisting in dicyclohexylphthalate-D4, methylpamitate and di-n-propylphthalateD4 was added to all samples (40 ng to water samples, 100 ng to sludge samples). The GC–MS analysis (Thermoquest Trace GC/MS System) was carried out on a DB-5 column (60 m 0.25 mm inner diameter, 0.25 lm film thickness) using the selected ion monitoring mode. Following temperature programme was employed: temperature increase from 60 to 185 °C with a temperature gradient of 15 °C min 1, holding 185 °C for 1 min, further temperature increase from 185 to 310 °C with a temperature gradient of 6 °C min 1 and held at 310 °C for 5 min. Injection temperature and transfer line temperature were set to 330 °C, source temperature to 255 °C. Limits of quantification (LOQ) as well as limits of detection (LOD) were dependent on sample matrix and volume, blank contamination as well as recovery ratios of the added deuterated surrogate standard. Basic validation was performed by using the statistical software package SQS in accordance with the German standard method DIN 32645 (DIN 32645, 1996). LOD and LOQ were calculated by multiplying those basic validation values with the enrichment factors and the recoveries of the analytes. LOQ and LOD of the investigated wastewater, sludge and road/surface runoff samples are provided in the respective result tables. Beside DBP recovery ratios of the deuterated surrogate standards ranged from 47% up to 125% (for DBP a maximum recovery ratio of 145% was observed) in the water samples and from 77% up to 108% in the sewage sludge samples. Measurements below the LOQ have been considered with the mean of LOD and LOQ and analytical results below the LOD were set equal to zero. 2.4. Sampling and sampling sites 2.4.1. Wastewater treatment plants Seventeen municipal wastewater treatment plants (WWTPs) of different treatment capacities (ranging from 2000 to 4 000 000 population equivalents, pe) and applying different treatment technologies (trickling filters, activated sludge) were sampled. All investigated WWTPs remove carbon and phosphorous and are nitrifying WWTPs. With exception of one plant all sampled WWTPs are also removing nitrogen by applying nitrification–denitrification processes. From 15 of those WWTPs daily composite influent and effluent samples were taken once, whereas from two WWTPs daily composite samples were taken over a period of 2 weeks. Based on these samples 2-d composite samples were mixed in the laboratory and subjected to chemical analysis. For these two WWTPs mass balances were calculated in order to illustrate the fate of the six phthalates during wastewater treatment. Beside the six phthalates also conventional wastewater parameters as COD, total nitrogen and total phosphorus (TP) were determined in all samples. These parameters served to assess general operation and performance of the sampled WWTPs and mass balances of TP and COD served as basis and plausibility control for the phthalates mass balances.
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2.4.2. Road/surface runoff At two stations along traffic roads samples from the surface runoff were taken. At one sampling station surface runoff from a motorway is collected, whereas the second sampling point was situated beside a street in a suburban area. From the motorway runoff grab samples were collected and from the suburban street flow proportional composite samples were taken. The yearly average daily traffic (ADT) on the motorway amounts to approx 42 000 vehicles d 1 of which ca 43% heavy traffic. The drained area at the suburban street includes vehicle and bicycle lanes as well as sidewalks. The ADT amounts to approx 24 000 vehicles d 1 of which ca 5% is attributed to heavy traffic. The sampled road section is exposed to wind (bridge) and characterised by stop and go traffic due to a traffic light. Both sampling stations were sampled four times from October to December 2008. 3. Results and discussion 3.1. Occurrence of phthalate esters 3.1.1. Wastewater Detection frequency as well as a summary of the measured concentrations of the six analysed phthalates in untreated and treated sewage in 15 WWTPs is provided in Table 2. In the influent DEP, BBP and DEHP were found in all samples, whereas detection frequencies for DMP, DBP and DOP amounted to 87%, 53% and 80%, respectively. In the effluent only BBP and DEHP were detected in all samples, whereas detection frequencies for DMP, DEP, DBP and DOP amounted to 60%, 80%, 53% and 7%, respectively. Beside DOP the detection frequencies in influent and effluent are comparable, but the concentrations measured in the influent are notably higher than those in the effluent, highlighting the removal capacity of municipal WWTPs for phthalates. In the influent as well as in the effluent the concentrations of the various phthalates varied strongly. The most abundant compound in the influent was DEHP (3.4–34 ng L 1), followed by DEP (0.77–9.2 ng L 1) and DBP (n.d. 8.7 ng L 1). The remaining phthalates BBP, DMP and DOP were of minor importance with concentrations around or below 1 lg L 1. In the effluent notably lower concentrations than in the influent were observed, but the distribution more or less remained unchanged. Also in the effluent DEHP
was the most abundant compound with concentrations ranging 0.083 up to 6.6 ng L 1, followed by DBP (n.d. 2.4 ng L 1) and BBP (0.088–1.4 ng L 1). DMP (n.d. 0.19) is of minor importance and DOP was detected only in one of the analysed effluent samples. Comparable distributions and comparable concentrations in influent and effluent were reported by Gasperi et al. (2008) and Dargnat et al. (2009). Also Marttinen et al. (2003) and Roslev et al. (2007) observed a comparable distribution but slightly higher concentrations. Higher effluent concentrations are reported also by Fromme et al. (2002) with DEHP ranging 1.74–182 lg L 1 and DBP ranging 0.2–10.4 lg L 1 in treated sewage and also by Marttinen et al. (2003) observing 6 lg L 1 of DEHP. Those higher concentrations in former studies may at least be partially explained by the fact, that DEHP is continuously replaced by other phthalate plasticizers. Specific pe loads in the influents were determined and referred to the industrial wastewater proportion. The industrial influence in the drainage area is calculated by determining the COD mass flux deriving from inhabitants with a specific COD load of 120 g COD pe 1 d 1 and referring this COD load to the total measured COD load in the sampled WWTPs. The difference is attributed to commerce and industry. In order to account uncertainties three categories are defined. Category 1 is a domestic area with influence of industry below 25%, category 2 has a mixed drainage area with industrial/commercial influences between 25% and 75% and category 3 is dominated by industry (more than 75% of the COD flux in the influent attributed to industry). Results for DEP and DEHP as the dominant phthalates are shown in Fig. 1. The specific pe discharges vary within a wide range, but highest values are calculated for drainage areas dominated by households and low industrial/commercial influences. This observation corresponds to the results reported by Vethaak et al. (2005) observing the highest phthalate concentrations in wastewaters from residential areas. 3.1.2. Road/surface runoff (stormwater) The measured concentrations of the analysed phthalate esters in the road runoff samples varied strongly (see Table 3). The most important compound in the runoff from traffic roads is DEHP with concentrations ranging 0.45–24 lg L 1, showing also the highest relative composition of total phthalate concentrations in all samples. In these samples also DINP and DIDP were analysed. Both
Table 2 occurrence of the six analysed phthalates in raw and treated wastewater (n = 15). Substance
Influent LOQ (lg L
a
1
)
Effluent LOD (lg L
1
)
n < LOD (–)
n > LOD (–)
DFa (%)
DMP
0.26–1.5
0.073–0.74
2
13
87
DEP
0.41–0.75
0.12–0.21
0
15
100
DBP
0.29–14
0.083–6.8
7
8
53
BBP
0.25–1
0.066–0.28
0
15
100
DEHP
0.23–0.28
0.061–0.075
0
15
100
DOP
0.48–0.95
0.13–0.26
3
12
80
DF: detection frequency; n.d.: not detected.
DFa (%)
Mean (min–max) (ng L 1)
Median (ng L 1)
9
60
0.062 (n.d.–0.19)
0.090
3
12
80
0.20 (n.d.–1.1)
0.15
0.044–4.8
7
8
53
0.54 (n.d.–2.4)
0.34
0.13–0.56
0.033–0.15
0
15
100
0.31
18
0.12–0.26
0.032–0.07
0
15
100
0.54
0.24–0.51
0.067–0.14
14
1
7
0.36 (0.088– 1.4) 1.6 (0.083– 6.6) 0.017 (n.d.–0.26)
Mean (min– max) (ng L 1)
Median (ng L 1)
LOQ (lg L
0.95 (n.d.– 2.4) 4.1 (0.77– 9.2) 2.2 (n.d.– 8.7) 0.95 (0.31– 3.2) 18 (3.4– 34) 0.49 (n.d.– 1.1)
0.88
0.14–0.81
0.04–0.4
6
3.9
0.23–0.4
0.065–0.11
0.76
0.15–9.6
0.9
1
)
LOD (lg L
1
)
n < LOD (–)
n > LOD (–)
0.50
n.d.
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M. Clara et al. / Chemosphere 78 (2010) 1078–1084
DINP was detected in all samples and the concentrations are comparable to those observed for DEHP varying from 0.22 up to 23 lg L 1. The other investigated phthalates beside DEHP and DINP are of minor importance, with concentrations all below 0.5 lg L 1. In order to make the various phthalates comparable, the measured concentrations were normalised to M. The relevance of the various phthalates in the investigated samples due to their relative proportions (average ± standard deviation) correspond to DINP (54 ± 15%), DEHP (38 ± 14%), DIDP (4.5 ± 7.4), DEP (1.5 ± 1.5%), DBP (0.9 ± 1.0%), DOP (0.6 ± 0.5%), DMP (0.4 ± 0.4%) and BBP (0.2 ± 0.2%). Hence DINP and DEHP contribute to approx 92 ± 21% of the overall phthalate emission. The detection frequencies for the phthalates were highest for DEHP, DEP and DINP (100%), followed by DOP (88%), DMP (75%), BBP and DBP (63%) as well as DIDP (38%). For all investigated phthalates a strong correlation to the total suspended solids concentrations in the samples is observed, confirming that phthalates in the runoff from traffic roads are to a large extend associated to particles. Thus is in line with the physical–chemical properties summarised in Table 1 showing high partitioning coefficients for the higher molecular phthalates. Only few data on the occurrence of phthalates in stormwater are available. Björklund et al. (2009) detected all phthalates in one or more stormwater samples, but significant variations in the concentrations occurred. Highest concentrations were observed for DINP (up to 85 lg L 1), DIDP (up to 17 lg L 1) and DEHP (up to 5.0 lg L 1) whereas the other five phthalic esters were detected in concentrations below 0.5 lg L 1 (Björklund et al., 2009). Beside the fact, that Björklund et al. (2009) document notably higher concentrations for DINP and DIDP the measured concentrations vary within a comparable range.
14
1a-DEHP 12
specific load [mg pe-1 d-1]
10 8 6 4 2 0 3.0
1b-DEP specific load [mg pe-1 d-1]
2.5 2.0 1.5 1.0 0.5 0.0
Category 1 1
Category 2
Category 3
1
Fig. 1. Specific pe loads (mg pe d ) for (a) DEHP and (b) DEP for the sampled wastewater treatment plants in dependence on the respective industrial influence.
compounds were detected in notable concentrations. DIDP was only found in a few samples but in concentrations up to 9.9 lg L 1.
Table 3 Measured concentrations of the analysed phthalic esters (lg L 1
)
DMP (lg L
1
)
1
) and total suspended solids (TSS) (mg L
DEP (lg L
1
)
DBP (lg L
1
)
BBP (lg L
1
)
1
) in road runoff samples.
DEHP (lg L
1
)
DOP (lg L
1
)
DINP (lg L
1
)
DIDP (lg L
Sampling site
TSS (mg L
LOQ LOD
– –
0.01 0.005
0.02 0.01
0.05 0.025
0.01 0.005
0.2 0.1
0.01 0.005
0.01 0.005
0.02 0.01
Motorway Sampling 1 Sampling 2 Sampling 3 Sampling 4
82 22 26 430
n.d. <0.01 n.d. 0.1
<0.02 0.051 0.021 0.27
n.d. n.d. n.d. 0.079
n.d. n.d. n.d. 0.33
5.3 2.4 0.45 24
0.061 0.01 n.d. 0.53
7.9 2.2 0.22 23
n.d. n.d. n.d. 9.9
Suburban area Sampling 1 Sampling 2 Sampling 3 Sampling 4
18 27 190 75
0.023 0.042 0.079 0.049
0.035 0.048 0.16 0.13
0.13 0.12 0.27 0.2
0.027 0.014 0.082 0.039
2.3 1.4 8.5 5.6
0.05 0.019 0.17 0.37
6.9 4.8 23 12
n.d. n.d. 0.53 4.8
1
)
n.d.: not detected.
Table 4 Measured phthalic esters concentrations in untreated and treated wastewater (lg L Wastewater LOQ (lg L
1
)
LOD (lg L
DMP DEP
0.1 0.1
0.05 0.05
DBP BBP DEHP DOP
0.1 0.1 0.2 0.1
0.05 0.05 0.1 0.05
n.d.: not detected.
1
) and in the sludge samples (lg kg
1
dry weight) of the two mass balance subjected WWTPs.
Sludge WWTP 1
WWTP 2
1
)
Influent (lg L 1)
Effluent (lg L 1)
0.26–0.41 n.d. 1.2–2 n.d.– < 0.1 <0.1–0.47 n.d. n.d.–0.11 n.d. 4.4–8.8 <0.2–0.28 n.d. n.d.
Influent (lg L 1)
Effluent (lg L 1)
LOQ (lg kg
1
)
LOD (lg kg
WWTP 1
WWTP 2
1
)
Primary sludge (lg kg 1)
Excess sludge (lg kg 1)
Primary sludge (lg kg 1)
Excess sludge (lg kg 1)
0.43–0.81 n.d. 2.2–2.7 n.d.
40 40
20 20
74 85
89 85
<40 61
56 70
n.d. 44
n.d. 55
n.d. 130
n.d. <40
0.15–0.41 0.11–0.26 4.1–13 n.d.– < 0.1
100 100 800 40
50 50 400 20
270 140 24 000 130
290 140 25 000 180
810 120 22 000 58
1200 130 27 000 96
310 180 20 000 140
850 380 27 000 260
– 250 27 000 89
640 200 29 000 120
n.d. n.d. <0.2–1.3 n.d.
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3.1.3. Fate of phthalates during wastewater treatment Two WWTPs have been investigated in detail in order to assess the fate of the six phthalates during wastewater treatment. Beside influent and effluent samples also primary and excess sludge were analysed twice for the six phthalates. Measured phthalate concentrations in untreated and treated wastewater as well as in sewage sludges are shown in Table 4. Both WWTPs operate a primary clarification followed by an activated sludge treatment. In WWTP 1 the excess sludge is pumped to the primary clarification where it is removed from the system together with the primary sludge. Totally approx 2350 kg sludge (in terms of TSS) are removed daily. In WWTP 2 primary sludge is removed from primary clarification (approx 5540 kg TSS d 1) whereas the excess sludge (approx 6845 kg TSS d 1) is removed from the sludge recycle. Mean daily inflow amounted to 7780 m3 d 1 in WWTP 1 and to 69 010 m3 d 1 in WWTP 2. Both WWTPs are removing nitrogen by nitrification/denitrification and operating sludge retention times of approx 17 d (WWTP 1) and 12 d (WWTP 2). Results of TP and phthalates mass balances for the two WWTPs are summarised in Fig. 2. As TP is not degraded, the fluxes in effluent and sludge have to be equal to the inflow flux. Therefore TP mass balance is an indicator for the quality of the balanced system. For both WWTPs sound results are obtained with WWTP 2 performing slightly better than WWTP 1. Beside BBP for both WWTPs a comparable distribution and behaviour of the investigated phthalates is observed. The overall removal via adsorption to sludge and biotransformation is higher than 95% for all compounds. Comparable overall removal for DEHP is reported also by Fauser et al. (2003) and Marttinen et al. (2003) and in EU-RAR (2008). Slightly lower overall removal for DEHP is observed by Tan et al. (2007) and Dargnat et al. (2009) whereas total efficiencies obtained for the other investigated phthalates are comparable.
Biotransformation Effluent Sludge
2a - WWTP 1
100 80 60 40
not applicable
specific flux [%] (referred to influent)
120
20 0
2b-WWTP 2
100 80 60 40
not applicable
specific flux [%] (referred to influent)
120
20 0 TP
DMP
DEP
DBP
BBP DEHP DOP
Substance Fig. 2. Mass balance results for the investigated phthalates in two WWTPs ((a) WWTP 1 and (b) WWTP 2).
It has to be considered, that most of the six phthalates were not detected in the effluent of the two WWTPs. In WWTP 1 only DEHP and in WWTP 2 DEHP and DEP were detected in the effluent samples. Setting analytical results below the LOD equal to zero the overall removal as well as the removal attributed to biotransformation are slightly overestimated. Nevertheless the results provide an estimate of the relevance of the two removal pathways. The importance of adsorption and the removal pathway via sludge increases with increasing molecular weight and with increasing lipophilic character of the substance (compare with log KOW values summarised in Table 1). This increasing relevance of adsorption with increasing log KOW is seen in both investigated WWTPs. In WWTP 1 (WWTP 2) the proportional mass fraction removed with the sludge amounts to 3.4% (0%) for DMP, 1.0% (0.7%) for DEP, 76% (64%) for DBP, 21% (74%) for BBP and 78% (81%) for DEHP. Comparable results for the overall removal (91%) for BBP and DBP are reported in the respective risk assessment reports (EU-RAR, 2004, 2007) but slightly higher removals due to biodegradation/biotransformation (50% and 58%) and slightly lower removal via adsorption (42% and 33%) to sludge is reported. A comparable result for DEHP is documented by Marttinen et al. (2003) and EU-RAR (2008). Marttinen et al. (2003) calculated an overall removal efficiency of 97%. Fourteen percent of the DEHP load in the influent is removed by biodegradation/biotransformation and 68% are removed by adsorption to primary and excess sludge. Modelling the removal of DEHP in a WWTP by applying the European Union System for the evaluation of substances, an overall removal efficiency of 93% is obtained, of which 15% are attributed to biodegradation/biotransformation and 78% to adsorption to sludge (EU-RAR, 2008). Fauser et al. (2003) observed higher impact of biodegradation on phthalates removal in WWTPs. Removal efficiencies of 60–70% due to biodegradation/ biotransformation were calculated whereas 20–35% are attributed to removal by sorption to primary and secondary sludge (Fauser et al., 2003). With the calculated removals and considering biomass concentrations in the reactors apparent degradation rate constants kbio were calculated according to the methodology described in Clara et al. (2005). For the calculation of kbio effluent concentrations were set equal to the LOQ as only DEHP was detected in the effluent samples, These estimates for kbio (L g 1 TSS d 1) were calculated with >4.3 and >5.2 for DMP, with >19 and 26 for DEP, with >0.50 and >0.98 for DBP, with >1.2 and >0.26 for BBP and with 1.6 and 4.1 for DEHP in WWTP 1 and WWTP 2, respectively. In the respective risk assessment reports (EU-RAR, 2004, 2007, 2008) DBP, BBP and DEHP are classified as ready biodegradable during wastewater treatment and a degradation rate constant of 1 h 1 is applied. For DBP and BBP notably lower kbio values were observed in the two WWTPs. A possible explanation is the substrate limitation in the biological reactor as all measured effluent concentrations were below the LOD, whereas the risk assessments rely on standardised tests applying high substrate concentrations in order to avoid substrate limitation. Only DEHP was quantified in the effluent. Considering usual TSS concentrations of 3–4 g L 1 in the biological reactor kbio ranges from 0.2 (WWTP 1) to 0.7 h 1 (WWTP 2). Phthalates also strongly tend to accumulate on sludge and the adsorbed mass seems not to be available for biodegradation anymore. Nevertheless the results highlight the high removal potential of biological wastewater treatment systems for phthalate removal from wastewater. Due to the limitations (effluent concentrations below LOQ) the provided values for kbio only can be rough estimates underrating the biodegradation potential but nevertheless they should be useful for a first assessment. In WWTP 2 DEHP was detected in the excess sludge as well as in the effluent. The aeration tank can be regarded as a completely mixed reactor with the dissolved effluent concentration corre-
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a
WWTP effluents Road runoff
10
1
0.1
0.01
100
relative concentration [-] c / cEQS
Concentration [µg L -1]
100
DEHP
DEP
DBP
10
1
1
0.1
BBP DEHP DOP
Fig. 3. Comparison (a) of the phthalate ester concentrations (lg L the EQS for DEHP for treated wastewater and road runoff.
1
100
10
0.1
0.01
DMP
b
0.01
WWTP effluent
Road runoff
) observed in treated wastewater and in road runoff and (b) relative DEHP concentrations (–) referred to
sponding to the dissolved concentration in the reactor. Based on this assumption it is possible to calculate an estimate for the solid–liquid distribution coefficient Kd from the measured values. Considering a mean effluent concentration of <0.20 lg L 1 and an average sludge concentration of 28 000 lg kg 1 an apparent Kd value of >140 000 L kg 1 (log Kd 5.15) is calculated. This calculated apparent Kd value is notably higher than those provided by Fauser et al. (2003) and applied in the risk assessment (EU-RAR, 2008) but it is within the range given in EU-RAR (2008). 3.1.4. Impact of emissions to surface water quality Directive 2008/105/EC defines an environmental quality standard (EQS) in surface waters for DEHP only and sets it equal to 1.3 lg L 1. In Fig. 3 the measured concentrations (mean, minimum and maximum) in the effluents of the investigated WWTPs (n = 15) as well as in the road runoff samples (n = 8) are shown. With exception of DEHP concentrations were notably higher in WWTP effluents than in road runoff. For DEHP the measured concentrations in WWTP effluents and in the road runoff samples are related to the EQS for DEHP (see Fig. 3). Whereas only in a few effluent samples DEHP concentrations exceeding the EQS were detected, in nearly all road runoff samples the ratio of the DEHP concentration in the sample and the EQS was higher than 1. This observation highlights the potential impact of surface water runoff emissions to surface waters. Obviously a pure comparison of concentration is not feasible and a more detailed assessment based on emitted fluxes and on mass balance considerations has to be performed. Nevertheless the results indicate that stormwater overflows as well as surface runoff to surface waters might have considerable impact on surface water quality. Especially considering the fact, that during the last decade a trend towards separate sewer systems was observed and only the sewage is treated in a WWTP whereas the surface runoff often is emitted to surface waters without any treatment. 4. Conclusions All investigated phthalates were detected in raw and treated sewage as well as in the runoff from roads. In the WWTPs a notable removal of up to 95% is observed which is attributed to biodegradation and adsorption to sludge. But even considering these removal efficiencies the emitted concentrations may exceed actual surface water quality standards. Especially in domestic areas and for WWTPs emitting to small receiving waters the emissions may be of relevance for those receiving water bodies. Beside emissions from WWTP also stormwater emissions as well as emissions from separated sewer systems may have a considerable impact on surface water quality. In order to make an in depth assessment of surface waters status with reference to xeno-
biotics on a catchment scale, further research is required to assess the relevance of other emission pathways than WWTPs. In this context one of the major difficulties is the assessment of frequency and duration of stormwater events and the collection of representative samples. Acknowledgement Parts of the work presented were financed by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management in cooperation with the nine Austrian Federal States. References AgPU, 2006. Plasticizers Market Data – Compiled by the Arbeitsgemeinschaft PVC und Umwelt e.V.
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