Removal of selected pharmaceuticals, fragrances and endocrine disrupting compounds in a membrane bioreactor and conventional wastewater treatment plants

Removal of selected pharmaceuticals, fragrances and endocrine disrupting compounds in a membrane bioreactor and conventional wastewater treatment plants

ARTICLE IN PRESS Water Research 39 (2005) 4797–4807 www.elsevier.com/locate/watres Removal of selected pharmaceuticals, fragrances and endocrine dis...

220KB Sizes 0 Downloads 5 Views

ARTICLE IN PRESS

Water Research 39 (2005) 4797–4807 www.elsevier.com/locate/watres

Removal of selected pharmaceuticals, fragrances and endocrine disrupting compounds in a membrane bioreactor and conventional wastewater treatment plants M. Claraa, B. Strenna, O. Gansb, E. Martinezb, N. Kreuzingera,, H. Kroissa a

Institute for Water Quality and Waste Management, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria b Umweltbundesamt GmbH, Spittelauer La¨nde 5, 1090 Vienna, Austria Received 10 September 2004; received in revised form 1 September 2005; accepted 13 September 2005 Available online 19 October 2005

Abstract Eight pharmaceuticals, two polycyclic musk fragrances and nine endocrine disrupting chemicals were analysed in several waste water treatment plants (WWTPs). A membrane bioreactor in pilot scale was operated at different solid retention times (SRTs) and the results obtained are compared to conventional activated sludge plants (CASP) operated at different SRTs. The SRT is an important design parameter and its impact on achievable treatment efficiencies was evaluated. Different behaviours were observed for the different investigated compounds. Some compounds as the antiepileptic drug carbamazepine were not removed in any of the sampled treatment facilities and effluent concentrations in the range of influent concentrations were measured. Other compounds as bisphenol-A, the analgesic ibuprofen or the lipid regulator bezafibrate were nearly completely removed (removal rates 490%). The operation of WWTPs with SRTs suitable for nitrogen removal (SRT410 days at 10 1C) also increases the removal potential regarding selected micropollutants. No differences in treatment efficiencies were detected between the two treatment techniques. As in conventional WWTP also the removal potential of MBRs depends on the SRT. Ultrafiltration membranes do not allow any additional detention of the investigated substances due to size exclusion. However, MBRs achieve a high SRT within a compact reactor. Nonylphenolpolyehtoxylates were removed in higher extend in very lowloaded conventional WWTPs, due to variations of redox conditions, necessary for the degradation of those compounds. r 2005 Elsevier Ltd. All rights reserved. Keywords: Wastewater treatment; Endocrine disrupting chemicals; Pharmaceuticals; Musk fragrances; Membrane bioreactor; Removal efficiency

1. Introduction Several pharmaceuticals, ingredients of personal care products and so-called endocrine disrupting compounds Corresponding author. Tel.: +43 1 58801 22622;

fax: +43 1 58801 22699. E-mail addresses: [email protected] (M. Clara), [email protected] (N. Kreuzinger).

(EDCs) (hormones and chemicals, which are suspected to have an impact on humans and wildlife hormone systems) are detected in surface waters in several European countries (Ternes, 1998; Fromme et al., 2002; Heberer, 2002a). Negative adverse health effects on aquatic organisms, which could be attributed to EDCs, are documented in various studies (Sonnenschein and Soto, 1998; Sumpter, 1998). Heberer (2002b) investigated the occurrence of pharmaceuticals in

0043-1354/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2005.09.015

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

4798

drinking water and in wastewater and tracked some persistent compounds from municipal sewage to drinking water. As the concentrations measured in the environment are in the range of nanogram per litre (ng l1) or a few microgram per litre (mg l1) they were often referred to as micropollutants. Most of those compounds are of anthropogenic origin and wastewater treatment plant (WWTP) effluents are important point discharges for the presence of endocrine disrupting compounds and residuals of pharmaceuticals in rivers, streams and surface waters. Therefore the elimination of these substances within the WWTP or their retention is of elementary interest. In conventional activated sludge plants (CASP) the aeration tank and the final clarifier form one process unit. The separation of treated sewage and sludge occurs in the clarifier via sedimentation. Therefore the ability to sediment is an important selection criterion. The biomass concentration in the mixed liquor is limited by the capacity of the clarifier. In membrane bioreactors this parameter is of minor influence, as separation is achieved via membrane filtration. Thus, the plant can be operated at higher biomass concentrations resulting in smaller plant sizes. The most important advantage of MBRs is the complete retention of suspended solids, thus reducing emissions to the dissolved fractions. Higher costs and higher requirements in operation and maintenance as well as power consumption compared to conventional systems are well-known disadvantages. MBRs are often highlighted regarding their potential to improve hazardous sub-

stances removal from sewage and their importance for the aquatic environment, respectively. One reason is linked to the complete retention of solids, as hydrophobic organic substances tend to accumulate onto the sludge. Furthermore, as all bacteria are held back, their adaptation to the more efficient mineralising of the respective compounds is possible (Ivashechkin et al., 2004). Another reason is that molecules larger than the molecular weight cut-off (MWCO) of the membrane cannot penetrate membrane pores due to size exclusion. However, only few comparative studies on the fate of organic micropollutants in MBRs and conventional systems are available. In wastewater treatment usually micro- and ultrafiltration membranes are used. During the last years the number of realized WWTPs equipped with membrane technology increased notably. Especially in regions with no suitable receiving waters or where treated wastewater is used for groundwater infiltration MBRs are suitable alternatives to conventional systems, also due to their disinfection capabilities. The purpose of the present study is neither the optimisation of operational settings at the investigated MBR pilot plant nor the optimisation in respect to nutrient removal. The study investigates the treatment efficiency of a MBR pilot plant equipped with an ultrafiltration membrane and operated at different solids retention times (SRTs) regarding the removal of selected micropollutants. The SRT describes the mean residence time of the biomass in the biological reactor. It is related to the growth rate of micro organisms, as only

Table 1 Investigated compounds (CAS number, molecular weight MW (g mol1)) and respective consumption (kg year1) in Austria according to Sattelberger (1999) and Skutan (2003) Category

Substance

CAS

Consumption

Diclofenac (DCF) Ibuprofen (IBP) Bezafibrate (BZF) Carbamaezpine (CBZ) Iopromide (IPM) Diazepam (DZP) Roxithromycin (ROX) Sulfamethoazole (SMX)

15307-86-5 15687-27-1 41859-67-0 298-46-4 73334-04-3 439-14-5 80214-83-1 723-46-6

6143 6696 4474 6334 5386 125 Not available 963

Musk fragrance Musk fragrance

Tonalide (AHTN) Galaxolide (HHCB)

1506-02-1 1222-05-5

Not available Not available

EDC EDC EDC EDC EDC EDC EDC EDC EDC

Bisphenol-A (BPA) Nonylphenol (NP) Nonylphenol monoethoxylate (NP1EO) Nonylphenol diethoxylate (NP2EO) Nonylphenoxyacetic acid (NP1EC) Nonylphenoxyethoxyacetic acid (NP2EC) Octylphenol (OP) Octylphenol monoethoxylate (OP1EO) Octylphenol diethoxylate (OP2EO)

80-05-7 25154-52-3 104-35-8 20427-84-3 3115-49-9 106807-78-7 140-66-9 2315-67-5 2315-61-9

14,500,000 7,000,000

Pharmaceutical Pharmaceutical Pharmaceutical Pharmaceutical Pharmaceutical Pharmaceutical Pharmaceutical Pharmaceutical

(analgesic) (analgesic) (lipid regulator) (antiepileptic) (contrast media) (tranquilizer) (antibiotic) (antibiotic)

Not available Not available Not available

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

organisms can be detained and enriched that are able to reproduce themselves during this time. WWTPs operating at high SRTs allow the enrichment of slowly growing bacteria and consequently the establishment of a more diverse biocoenosis with broader physiological capabilities (e.g. nitrification). The results observed in the MBR are compared to several conventional WWTPs. Eight pharmaceuticals, two polycyclic musk fragrances and nine endocrine disrupting chemicals were studied (see Table 1).

2. Materials and methods 2.1. Analytical methods Different analytical methods were applied to determine the concentration levels of the analytes in the water samples. Analyses were performed by the Austrian Umweltbundesamt. Statistical evaluation of measurements and determination of limits of quantification (LOQ) were based according to DIN 32645 (1994). Indicated recoveries are mean recovery rates for the whole analytical method, including all steps of the analytical process. Alkylphenols and alkylphenol ethoxylates are present in plastics and detergents and glassware required special treatment prior to use. Therefore, case was taken to avoid—as far as possible—plastics for sampling since traces of the surveyed industrial chemicals may leach the plastics into the sample. Layered sampling bottles (aluminium, 1.2 l; Bu¨rkle, Germany) to avoid contact of the sample with the plastic screw mount were provided by the Umweltbundesamt. The material can withstand freezing of the sampling bottle. In order to avoid contamination, bottles were regularly cleaned, rinsed with acetone and water and heated up to 110 1C over night. Afterwards, they were rinsed with isooctane in order to deactivate the surface and were dried until the remaining solvent evaporated. In the case of the selected pharmaceuticals and personal care products, also aluminium bottles, 1,2 l (Bu¨rkle, Germany) were used for the sampling and the samples were stabilized with sodium azide. For the analysis of the selected EDCs, 500 ml water samples were acidified with sulphuric acid to pHp3 and 25 ml of surrogate standard (BPA-d16 and NP1EC-d2) was added. The conditioning and loading steps were carried out automatically by the Auto Trace extraction Work Station (Zymark, Hopkinton, MA, US), using C18 phase cartridges (1 g, 6 ml). After drying with nitrogen for 20 min, the compounds were eluted by acetone and a mixture of methanol/methyl-tert.-butylether (1:9). The extracts were evaporated in a Turbo Vap II (Zymark, Hopkinton, MA, US) to 0.5 ml by nitrogen and filled up to a final volume of 1 ml with

4799

acetonitrile (ACN). 10 ml of internal standard (4-n-NP, BPA-d8) was added prior to analysis. LC-MS/MS applying electro spray ionisation (ESI) was used for the determination of the analytes. BPA, NP, OP and NP1,2ECs were detected in the negative ion mode, whereas the NPEOs and OPEOs were analysed in the positive ion mode. A detailed description of the analytical method for the determination of alkylphenols is given in Marı´ tnez et al. (2004). To analyse CBZ, IPM, DZP, SMX and ROX, two different solid phase extraction methods with CH (1 g, 6 ml) and ENV+ (200 mg, 6 ml) phases were employed. In the first method 500 ml samples were acidified, whereas in the second method a neutral EDTA buffer was used. Prior to sample extraction a surrogate standard (josamycine, tylosine and dihydro-CBZ) was added to the samples. The conditioning, loading and elution steps were carried out automatically. The analytes were eluted with methanol, ethyl acetate and dichloromethane, in the case of the acidic sample preparation, and with ACN and a mixture of acetonitril/water/tri-ethyl-amine, in the case of neutral sample preparation. The extracts were evaporated to below 0.5 ml and then filled up to a final volume of 1 ml with ACN/H2O 1:9. These compounds were analysed by LCMS/MS with ESI in the positive ion mode. To overcome problems due to ion suppression in the LC-MS method, recoveries of the surrogate standard and measurements of multiple dilutions of the extracts were performed. IBP, DCF, BZF, AHTN and HHCB were separated and analysed by GC-(ESI)MS in the multiple ion detection (MID) mode. Analytes were enriched by solid phase extraction on a RP-18 (3 g, 6 ml) column under acidic conditions. Prior to sample extraction a surrogate standard (meclofenamic acid and AHTN-D3) was added to the samples. After elution with ethyl acetate and dichloromethane a derivatization step with diazomethane was performed, followed by a cleaning up step with silica gel. The extracts were filled up to 1 ml after addition of 50 ml internal standard (decachlorbiphenyl). The results were corrected by the added surrogate standards, where it was possible. In the case where no appropriate surrogate standards were available the results were corrected by the recovery performed in the same serie. Mean recovery rates, the LOQ and the limits of detection (LOD) for the different investigated compounds are summarised in Table 2. 2.2. Membrane bioreactor The MBR is a pilot scale plant situated at the premises of a conventional WWTP (WWTP 1). From the grit chamber of the conventional plant the wastewater is pumped into a feed tank, from which the denitrification vessel is charged. In addition to the mechanic treatment of the full scale plant a 1 mm punched sieve is installed at

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

4800

Table 2 Investigated compounds, limits of detection (LOD) and quantification (LOQ) in ng l1 and mean recovery rates (%) Substance

Formula

MW

LOD (ng l1)

LOQ (ng l1)

a

a

Recovery (%)

DCF IBP BZF CBZ IPM DZP ROX SMX

C14H11Cl2NO2 C13H18O2 C19H20ClNO4 C15H12N2O C18H24I3N3O8 C16H13ClN2O C41H76N2O15 C10H11N3O3S

296.16 206.29 361.83 236.28 791.15 284.70 837.06 253.31

10 (50 ) 10 (50a) 10 (50a) 10 10 10 10 10

20 (100 ) 20 (100a) 20 (100a) 20 20 20 20 20

98 97 99 75 98 88 65 84

AHTN HHCB

C18H26O C18H26O

258.40 258.40

10 20

20 40

83 88

BPA NP NP1EO NP2EO NP1EC NP2EC OP OP1EO OP2EO

C15H16O2 C14H22O C17H28O2 C19H32O3 C17H26O3 C19H30O4 C15H24O C16H26O2 C18H30O3

228.20 220.36 264.41 308.46 278.39 322 206.33 250.38 294

10 10 10 10 10 10 10 10 10

20 20 20 20 20 20 20 20 20

80 79 72 66 90 90 82 89 84

a

Inflow samples.

Table 3 Characterisation of the investigated MBR pilot plant and the sampled conventional activated sludge WWTPs T (1C)

SRT (d)

HRT (d)

TSS (g l1)

VSS TSS1 ()

F/M (g COD g TSS1 d1)

MBR 1st sampling 2nd sampling 3rd sampling

22.2 27.2 5.5

10 27 55

0.5 1.2 4.0

6.3 4.5 11.8

0.75 0.71 0.79

0.24 0.16 0.03

WWTP1 1st sampling 2nd sampling 3rd sampling

16.8 22.1 6.8

114 237 52

13.3 12.5 13.6

4.9 4.0 4.0

0.65 0.60 0.68

0.02 0.02 0.02

WWTP 2

13.5

2

0.08

4.0

0.80

1.70

WWTP 3

10.4

46

1.20

3.1

0.65

0.04

the extraction point, reducing the amount of particulate matter and fibres entering the plant. From the nitrification tank the sludge is pumped to the external situated cross flow membrane module, where an ultrafiltration membrane is installed. The sludge is recycled to the nitrification vessel and the permeate is stored in a permeate tank. The membrane module is regularly backwashed with treated wastewater from the permeate tank. An internal sludge recycle connects nitrification and denitrification to avoid biomass accumulation in the nitrification tank and to obtain further nitrogen removal. The excess sludge is removed from this internal sludge recycle. Both nitrification and denitrification have

a volume of 2.5 m3. Whereas the nitrification tank is continuously aerated, the denitrification tank is mixed by an electric stirrer. No phosphorous precipitation occurred. The MBR was run with different operational settings. Different SRTs were installed during three investigation periods. Characteristic data on the MBR are summarised in Table 3. 2.3. Conventional wastewater treatment The conventional activated sludge WWTP, where the MBR pilot plant is installed, serves a rural community

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

in the South-East of Austria and is designed for 7000 population equivalents (pe). The design capacity is based on 100 g chemical oxygen demand (COD) pe1 day1. Actually approx. 3000 pe are connected to the sewer system. The treatment plant is charged with domestic sewage from a separated sewer system without industrial influents and with strong seasonal fluctuations due to local viniculture. These strong fluctuations are illustrated by means of the COD in the influent. While the mean COD concentration in the influent in 2002 was 1080 mg l1, the maximum 2 weeks mean was 1900 mg l1 and peak values of more than 6000 mg l1 COD were measured in daily composite inflow samples. The sewage plant is operated with simultaneous sludge stabilisation and simultaneous phosphorus precipitation with ferric chloride (FeCl3). Nitrogen removal is achieved by simultaneous and intermittent nitrification and denitrification. The WWTP consists of screen and grit chamber, two aeration tanks (1546 m3 each) and two secondary clarifier for final sedimentation. The excess sludge is removed very infrequently resulting in high SRTs. This conventional WWTP was sampled in parallel to the MBR. In order to compare the results observed for the different SRTs in the MBR, two CASP operating different SRTs were sampled. Twenty four hours composite samples were taken by automatic sampling and preserved by cooling. WWTP2 is a highly loaded plant, designed for carbon removal only. WWTP3 is a low-loaded plant designed for nutrient removal. Characteristic data as temperature (T), SRT, hydraulic retention time (HRT), total suspended solids concentrations (TSS), volatile suspended solids concentrations (VSS) and food to microorganism ratios (F/M) expressed in terms of COD are summarised in Table 3. 2.4. Mass balances A plausibility analysis of the measured values was made, using mass balances for phosphorus, nitrogen and COD according to Nowak et al. (1999). Based on that data, an evaluation of process characteristics (e.g. SRT, specific excess sludge production, etc.) was performed. The most important removal pathways an organic compound is subjected during wastewater treatment are stripping by aeration (volatilisation), adsorption to the sludge (excess sludge removal) and biotransformation/biodegradation. Considering octanol–water partitioning (log POW) and Henry coefficients (KH) of the investigated substances and the aeration systems in the different WWTPs, volatilisation is negligible for most of the selected substances (Struijs et al., 1991; Rogers, 1996). Only in WWTP2 operating superficial aeration systems for the two musk fragrances AHTN and HHCB volatilisation may be of importance.

4801

Daily (24-h) composite samples (time-weighted) of influent and effluent were taken by automated samplers preserved by cooling and filtered by fluted filters. The samples were transported to the analysing institute and the dissolved concentrations were measured. The calculations of the mass balances are based on those measured dissolved concentrations. The absorbed fractions were considered by the application of equilibrium solid/liquid partition coefficients KD. From the investigated substances the EDCs and the musk fragrances are relevant for adsorption and have KD-values higher than 1000 l kg1, whereas for the investigated pharmaceuticals (KD-values below 100 l kg1) adsorption processes are negligible (Ahel et al., 1994; Clara et al., 2004b; Ternes et al., 2004). Removal from the liquid phase corresponds to the difference between influent and effluent mass fluxes. Biodegradation/biotransformation is the removal minus the mass flux removed from the system with the excess sludge. A mathematical description of the mass balances is summarised in Clara et al. (2005).

3. Results and discussion 3.1. Pharmaceuticals and personal care products (PPCPs) Mean dissolved concentrations of the PPCPs in influent and effluent of the investigated WWTPs are summarised in Table 4. The tranquilizer diazepam was not detected in any of the analysed samples. The absence of this compound is explained by the low consumption in Austria, amounting to 125 kg year1 in 1997 (Sattelberger, 1999). The contrast media iopromide was not present in the influent of WWTP1 and the MBR, what is explained with the absence of a hospital in the drainage area. In WWTP2 high concentrations of IPM were measured. Mean measured influent concentrations amounted to 3840 ng l1, and mean measured effluent concentrations to 5060 ng l1. No reasonable justification for the increasing of IPM concentrations within the WWTP could be identified. The antibiotic SMX was only found during the 1st sampling in May. ROX was detected during all sampling campaigns, but notably higher concentrations were detected during the 3rd sampling in December compared to the samplings in May and July. Considering the relatively constant influent flow rates during the three sampling campaigns (240726, 255725, 235725 m3 d1) this fact indicates a seasonal variation of antibiotics in the influent and may be related to higher consumptions during the cold period of the year. This statement remains an assumption as no data on consumption rates for the relevant period are available. Comparable results

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

4802

Table 4 Mean dissolved concentrations (ng l1) of PPCPs in inflow and effluent of the investigated WWTPs DCF

IBP

BZF

CBZ

IPM

DZP

ROX

SMX

AHTN

HHCB

1st sampling Inflow WWTP1 effluent MBR effluent

3250 1536 3464

1480 n.d. 22

1960 n.d. 103

1850 1594 1619

n.d. n.d. n.d.

n.d. n.d. n.d.

26 41 n.d.

145 50 56

1106 145 163

3060 451 455

2nd sampling Inflow WWTP1 effluent MBR effluent

4114 1533 2033

2679 n.d. 22

2014 n.d. 73

1200 1337 1147

n.d. n.d. n.d.

n.d. n.d. n.d.

64 36 42

n.d. 18 n.d.

989 170 92

4443 600 373

3rd sampling Inflow WWTP1 effluent MBR effluent

3190 1680 2140

2448 20 69

6840 692 1550

704 952 794

n.d. n.d. n.d.

n.d. n.d. n.d.

117 69 31

n.d. n.d. n.d.

1046 144 148

3360 652 536

WWTP2 Inflow Effluent

1400 1300

2300 2400

7600 4800

670 690

3840 5060

n.d. n.d.

78 57

24 91

450 160

1400 870

WWTP3 Inflow Effluent

905 780

1200 24

1550 715

325 465

26 250

n.d. n.d.

25 45

75 51

210 170

830 535

were obtained by McArdell et al. (2003) reporting two times higher inflow loads during wintertime than during summer. Considering the low tendency of the antibiotics to accumulate onto sludge, removal rates between 50% and 60% were achieved. But especially in the case of antibiotics it has to be annotated, that metabolites should be included in the mass balances as a significant amount enters WWTPs in metabolised form, e.g. SMX as N4-Acetyl-SMX (Go¨bel et al., 2004). The other PPCPs were detected in all investigated plants during all sampling campaigns. Except in WWTP2, lower effluent than influent concentrations were measured for BZF, IBP, AHTN and HHCB indicating a notable removal potential during wastewater treatment (see Fig. 1). For these substances comparable effluent concentrations and removal rates were observed in the conventional activated sludge plant and the MBR. In WWTP2 no or only slight removal rates were achieved. Those low removal rates are attributed to the low SRT installed in the plant (Clara et al., 2005). The antiepileptic carbamazepine is not removed during wastewater treatment. In all investigated treatment facilities effluent concentrations in the range of the respective influent concentrations were measured (Clara et al., 2004a). Contradictory results were observed for DCF. Whereas in WWTP1 removal rates of up to 70% were calculated, no removal was observed in the other conventional WWTPs. In the MBR no removal

occurred during the first sampling campaign, when the plant was operated with a SRT of approx. 10 days. Dissolved effluent concentrations in the range of influent concentrations were measured. From this observation can be concluded, that the membrane does not detain the substance by size exclusion. With increasing SRT also in the MBR a partial removal of DCF is observed. No reasonable explanation for these findings could be found. The authors were not able to identify why only in WWTP1 remarkable removal of DCF occurred whereas in the other sampled WWTPs no similar behaviour was observed. But also in literature similar contradictory observations are reported. Whereas Zwiener and Frimmel (2003) and Heberer (2002a) report no significant elimination of diclofenac, Ternes (1998) documented elimination rates of up to 70%. 3.2. Endocrine disrupting compounds (EDCs) Mean measured influent and effluent concentrations of the EDCs are summarised in Table 5. BPA is nearly completely removed (495%) in WWTP1 as well as in the MBR and comparable dissolved effluent concentrations were measured. Considering the low effluent concentrations, biodegradation/biotransformation processes are the main removal pathway for BPA. In WWTP2 no removal was observed, indicating a dependency of degradation on the SRT as WWTP2 is a highly loaded plant, operating at SRTs between 1 and 2 days.

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

Sorption to sludge

Removal 120

Biodegradation/biotransformation 120

IBP

BZF

3

2

TP

TP

W W

W W

M

BR

III

II

I M

BR

BR

TP W

W

W

W

W W

120

M

1I

3 TP

TP

III W

BR M

W

I M

BR

BR

M

W

W

TP

TP

TP W

W

W W

2

-20

II

-20

1III

0

1II

0

1III

20

1II

20

40

TP

40

60

W

60

80

TP

80

W

relative amount [%]

100

1I

120

AHTN

HHCB

100

3 TP

2 W W

W

W

TP

III

II

BR M

M

BR

I BR

1III

M

TP W W

W

W

TP

1I

3

2 TP

III W W

BR M

M

BR

I BR

M

TP W

W

W

W

TP

TP W W

II

-20

1III

-20

1II

0

1I

0

1II

20

TP

20

40

W

40

60

TP

60

80

W

80

W

relative amount [%]

100

W

relative amount [%]

100

relative amount [%]

4803

Fig. 1. Removal of ibuprofen, bezafibrate, tonalide and galaxolide by adsorption to the sludge and biodegradation/biotransformation in the investigated wastewater treatment facilities ( removal, ’ sorption, & biodegradation/biotransformation).

Nonylphenol, nonylphenol ethoxylates and the nonylphenol carboxylates cannot be treated substance by substance. Due to the interactions between the different fractions an integrated evaluation of the behaviour of those compounds during wastewater treatment has to be performed. Biodegradation of nonylphenol polyethoxylates (NPnEOs) in wastewater treatment plants or in the environment is generally believed to start with a shortening of the ethoxylates (EO) chain, generating more persistent shorterchain NPEOs and NP (Ying et al., 2002). Partial NPnEO degradation seems to occur already in the sewer system as NP1EO is the dominant fraction in the influent of the sampled WWTPs. Further transformation proceeds via oxidation of the EO chain, producing mainly nonylphenoxy ethoxy acetic acid (NP2EC) and nonylphenoxy acetic acid (NP1EC) (Ying et al., 2002). According to Brunner et al. (1988) NPnEOs are degraded more easily under aerobic, than under anaerobic, conditions, whereas a complete deethoxyla-

tion with formation of NP was observed under anaerobic conditions only (Ahel et al., 1994). As described in literature (Ying et al., 2002; Ahel et al., 1994), a change in the distribution of NP, NPEOs and NPECs was observed between inflow and effluent. Whereas in the influent NP and NP1EO were the main fractions, in the effluent NP1EC and NP2EC predominated (see Fig. 2). The following numbers (a  b) indicate the proportionate fractions of the sum of NP, NPEO and NPEC and the respective standard deviations (n ¼ 19). In WWTP1 and the MBR NP contributed to approx. 32714% and NP1EO to 51713% to the influent, whereas NP2EO (775%), NP1EC (674%) and NP2EC (372%) are of minor importance. In the effluent the distribution shifts to nonylphenol carboxylates. In the effluent of WWTP1 (MBR) the relative fractions amount to 1977% (1678%) for NP, to 373% (472%) for NP1EO, to 272% (271%) for NP2EO, to 5379% (58715%) for NP1EC and to

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807

4804

Table 5 Mean dissolved concentrations (ng l1) of EDCs in inflow and effluent of the investigated WWTPs BPA

NP

NP1EO

NP2EO

OP

OP1EO

OP2EO

1st sampling Inflow WWTP1 effluent MBR effluent

2025 26 28

4031 487 371

7116 84 192

866 69 133

724 905 2039

362 196 589

118 29 65

213 20 19

36 n.d. 15

2nd sampling Inflow WWTP1 effluent MBR effluent

2376 35 16

2673 280 297

7299 n.d. 38

767 n.d. 44

737 1117 4900

107 290 1047

436 n.d. n.d.

552 n.d. n.d.

55 n.d. n.d.

3rd sampling Inflow WWTP1 effluent MBR effluent

2151 76 158

3129 326 482

4450 64 93

835 78 60

429 1544 1164

471 1648 874

215 15 74

42 n.d. n.d.

n.d. n.d. n.d.

WWTP2 Inflow Effluent

1710 1530

1950 370

4060 2580

600 1360

490 4730

840 8530

680 90

660 470

n.d. 150

WWTP3 Inflow Effluent

720 125

1280 285

6905 141

4645 78

2325 5235

3635 7760

146 106

281 n.d.

114 n.d.

120

WWTP 1 100 80 60 40 20

cumulative frequency [%]

cumulative frequency [%]

120

0

MBR

100 80 60 40 20

NP1EO NP2EO NP1EC NP2EC

NP

WWTP 2

100 80 60 40 20 0

NP1EO NP2EO NP1EC NP2EC

120

cumulative frequency [%]

cumulative frequency [%]

180 120

NP2EC

0

NP 200

NP1EC

WWTP 3 100 80 60 40 20 0

NP

NP1EO NP2EO NP1EC NP2EC

NP

NP1EO NP2EO NP1EC NP2EC

Fig. 2. Cumulative frequencies of nonylphenol and nonylphenolethoxylates in inflow and effluent ( inflow, & effluent) of the investigated treatment plants, with 100% equal to 44.5 nmol l1 (WWTP1), 44.5 nmol l1 (MBR), 30.5 nmol l1 (WWTP2) and 66.6 nmol l1 (WWTP3).

22714% (2078%) for NP2EC and no differences between the conventional activated sludge plant (WWTP1) and the MBR were detected. Also in WWTP2 and WWTP3 this shifting in the distribution between NP, NPEOs and NPECs can be observed.

Different removal rates were calculated for the alkylphenolic compounds in the different investigated WWTPs. The results of the mass balances are summarised in Fig. 3. The highest removal rates were observed in WWTP1, achieving more than 90%. The

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807 Sorption to sludge

Removal

Biodegradation/biotransformation

NP+NPEO+NPEC

120

OP+OPEO

120

100

40

TP

1III M BR I M BR II M BR III W W TP 2 W W TP 3

1I

1-

TP W

M

BR

W

W

TP

TP

TP

W

W W

W

I M BR II M BR III W W TP 2 W W TP 3

-20

III

-20 1II

0

1I

0

1II

20

W

20

60

TP

40

80

W

60

W

80

W

relative amount [%]

100

W

relative amount [%]

4805

Fig. 3. Removal of alkylphenols and alkylphenol ethoxylates by adsorption to the sludge and biodegradation/biotransformation in the investigated wastewater treatment facilities ( removal, ’ sorption, & biodegradation/biotransformation).

MBR showed comparable results. Significantly lower removal of alkylphenolic compounds occurred in WWTP3 and no removal was observed in the high loaded WWTP2. A complete degradation of alkylphenol ethoxylates requires an anaerobic treatment step in order to obtain a de-ethoxylation (Ahel et al., 1994). WWTP2 is continuously aerated and in the effluent aerobic degradation metabolites as NP1EO and NP1EC are accumulated. WWTP3 operates an anaerobic cascade for biological phosphorous removal, but as in WWTP2 also in WWTP3 an accumulation of nonylphenol carboxylates is observed. Due to the anaerobic cascade and the low loading of the plant higher removal rates would be expected to occur. No reason for those comparably low removal rates could be found. WWTP1 is a very low-loaded plant achieving very high SRTs. Mean daily aeration time’s amount to approx. 5 h and especially during summer the formation of anaerobic zones in the biological reactor is realistic. Due to this and the high retention times a nearly complete removal occurs. Comparable results are reported by Ahel et al. (1994). The authors observed the highest removal rates for NPEOs in low-loaded conventional municipal WWTPs. In the MBR anaerobic zones are expected to appear in the denitrification tank due to high organic loading. In the MBR the sludge recirculation is important in order to avoid sludge concentration in one compartment of the plant. Oxygen transfer from the aerated compartments to the denitrification due to this sludge recirculation may influence the removal of alkylphenolic compounds and be the reason for the slightly lower removals in the MBR compared to WWTP1. Summarising it can be stated that only negligible differences in the removal potential for the investigated substances could be detected between conventional

WWTPs and the sampled MBR. This observation leads to the conclusion, that the operated ultrafiltration membrane does not allow any further retention of the investigated substances and degradation is dependent on the operated SRT (Clara et al., 2005). Comparable results for BPA and NP are reported also by Ivashechkin et al. (2004) and comparable observations for pharmaceuticals are reported by Joss et al. (2005). Considering the molecular weight of the investigated compounds (see Table 2), an additional detention due to pure filtration effects by the applied ultrafiltration membrane based on size exclusion is not to be expected (Stephenson et al., 2000).

4. Conclusions Comparable effluent concentrations and removal rates for the different investigated substances were observed in the conventional WWTP and the membrane bioreactor. Some substances are not removed during wastewater treatment (e.g. carbamazepine). They pass the investigated plants without any reduction and effluent concentrations in the range of influent concentrations were measured. Other substances as BPA, IBP, BZF, etc are degraded during wastewater treatment, achieving notable removal rates of more than 90% and resulting in low-effluent concentrations. For these compounds only slight differences in the effluent concentrations could be detected between conventional activated sludge wastewater treatment and membrane bioreactors. This observation leads to the conclusion, that the operated ultrafiltration membrane does not allow any further retention of the investigated substances due to size exclusion. Dense membranes as usually applied in reverse osmosis and/or nanofiltration

ARTICLE IN PRESS 4806

M. Clara et al. / Water Research 39 (2005) 4797–4807

processes would be required, to detain the substances investigated in the present study; this would add further to the increased power consumptions of MBRs. Nevertheless the MBR offers advantages compared to conventional systems. The membrane allows the detention of particulate matter leading to an effluent free of suspended solids. Slightly lower total emissions can be achieved in MBRs compared to conventional WWTPs for strongly adsorbing substances. MBRs achieve high SRTs within compact reactor volumes and as degradation is a function of the operated SRT, this fact represents another advantage of MBRs in comparison to conventional systems. Especially in regions with no suitable receiving waters or where a reuse of the treated wastewater is planned, MBRs represent an attractive solution due to the mentioned advantages.

Acknowledgments The results presented in this work were obtained within the EU-funded project POSEIDON (EVK1-CT2000-00047), the ARCEM project (Austrian Research Cooperation on Endocrine Modulators) funded by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management, Kommunalkredit Austria AG and the nine Austrian Federal States. The results for the membrane bioreactor were derived from the VALIUM project (Verhalten von bestimmten ArzneimitteLru¨cksta¨nden, Industrie- und Umweltchemikalien in Membranbioreaktoren), funded by the Government of Burgenland, Department Gewa¨sseraufsicht. The authors acknowledge the VA-TECH WABAG for installation and operation of the membrane pilot plant.

References Ahel, M., Giger, W., Koch, M., 1994. Behaviour of alkylphenol polyethoxylate surfactants in the aquatic environment—I. Occurrence and transformation in sewage treatment. Water Res. 28 (5), 1131–1142. Brunner, P.H., Capri, S., Marcomini, A., Giger, W., 1988. Occurrence and behaviour of linear alkylbenenesulphonates, nonylphenol, nonylphenol mono- and nonylphenoldiethoxylats in sewage and sewage sludge treatment. Water Res. 22 (12), 1465–1472. Clara, M., Strenn, B., Kreuzinger, N., 2004a. Carbamazepine as a possible anthropogenic marker in the aquatic environment: investigations on the behaviour of Carbamazepine in wastewater treatment and during groundwater infiltration. Water Res. 38 (4), 947–954. Clara, M., Strenn, B., Saracevic, E., Kreuzinger, N., 2004b. Adsorption of bisphenol-A, 17b-estradiole and 17a-ethinylestradiole to sewage sludge. Chemosphere 56 (9), 843–851.

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 (1), 97–106. DIN 32645, 1994. Chemische Analytik; Nachweis-, Erfassungsund Bestimmungsgrenze; Ermittlung unter Wiederholbedingungen; Begriffe, Verfahren, Auswertung. Beuth Verlag GmbH, Berlin-Wien-Zu¨rich. Fromme, H., Ku¨chler, T., Otto, T., Pilz, K., Mu¨ller, J., Wenzel, A., 2002. Occurrence of phthalates and bisphenol A and F in the environment. Water Res. 36 (6), 1429–1438. Go¨bel, A., McArdell, C.S., Suter, M.J.F., Giger, W., 2004. Trace determination of macrolide and sulfonamide antimicrobials, a human sulfonamide metabolite, and trimethoprim in wastewater using liquid chromatography coupled to electrospray tandem mass spectrometry. Anal. Chem. 76 (16), 4756–4764. Heberer, T., 2002a. Occurrence, fate and removal of pharmaceutical residues in the aquatic environment: a review of recent research data. Toxicol. Lett. 131 (1–2), 5–17. Heberer, T., 2002b. Tracking persistent pharmaceutical residues from municipal sewage to drinking water. J. Hydrol. 266 (2–3), 175–189. Ivashechkin, P., Corvini, P., Fahrbach, M., Hollender, J., Konietzko, M., Meesters, R., Schro¨der, H.F., Dohmann, M., 2004. Comparison of the elimination of endocrine disrupters in conventional wastewater treatment plants and membrane bioreactors. In: Conference Proceedings of the Second IWA Leading-Edge Conference on Water and Wastewater Treatment Technologies, 1–4 June 2004, Prague, Czech Republic. Joss, A., Keller, E., Alder, A.C., Go¨bel, A., McArdell, C.S., Ternes, T., Siegrist, H.R., 2005. Removal of pharmaceuticals and fragrances in biological wastewater treatment. Water Res. 39 (14), 3139–3152. Martı´ nez, E., Gans, O., Weber, H., Scharf, S., 2004. Analysis of nonylphenol polyethoxylates and their metabolites in water samples by high-performance liquid chromatography with electrospray mass spectrometry detection. Water Sci. Technol. 50 (5), 157–163. McArdell, C.S., Molnar, E., Suter, M.J.F., Giger, W., 2003. Occurrence and fate of macrolide antibiotics in wastewater treatment plants and in the Glatt Valley watershed, Switzerland. Environ. Sci. Technol. 37 (24), 5479–5486. Nowak, O., Franz, A., Svardal, K., Mu¨ller, V., Ku¨hn, V., 1999. Parameter estimation for activated sludge models with the help of mass balances. Water Sci. Technol. 39 (4), 113–120. Rogers, H.R., 1996. Sources, behaviour and fate of organic contaminants during sewage treatment and in sewage sludges. Sci. Total Environ. 185 (1–3), 3–26. Sattelberger, R., 1999. Arzneimittelru¨cksta¨nde in der UmweltBestandsaufnahme und Problemdarstellung. Reports R162, Umweltbundesamt GmbH. Vienna, Austria, ISBN 385457-510-6. Skutan, S., 2003. Risikomanagement: Modulteil Stoffstromanalysen. In: Umweltbundesamt GmbH (Ed.), Hormonwirksame Stoffe in O¨sterreichs Gewa¨ssern—Ein Risiko? Final Report, July 2003, Vienna, Austria, IV-14–IV-45, ISBN 3-85457-695-1. Available from http://www.arcem.at/ endbericht.pdf

ARTICLE IN PRESS M. Clara et al. / Water Research 39 (2005) 4797–4807 Sonnenschein, C., Soto, A.M., 1998. An updated review of environmental estrogen and androgen mimics and antagonists. J. Steroid Biochem. 65 (1–6), 143–150. Stephenson, T., Judd, S., Jefferson, B., Brindle, K., 2000. Membrane Bioreactors for Wastewater Treatment. IWA Publishing, London, UK. Struijs, J., Stoltenkamp, J., Meent, D.V.D., 1991. A spreadsheet-based box model to predict the fate of xenobiotics in a municipal treatment plant. Water Res. 25 (7), 891–900. Sumpter, J.P., 1998. Xenoendocrine disrupters—environmental impacts. Toxicol. Lett. 102–103, 337–342. Ternes, T.A., 1998. Occurrence of drugs in German sewage treatment plants and rivers. Water Res. 32 (11), 3245–3260.

4807

Ternes, T., Hermann, N., Bonerz, M., Knacker, T., Siegrist, H.R., Joss, A., 2004. A rapid method to measure the solid–water distribution coefficient (Kd) for pharmaceuticals and musk fragrances in sewage sludge. Water Res. 38 (19), 4075–4084. Ying, G.-G., Williams, B., Kookana, R., 2002. Environmental fate of alkylphenols and alkylphenol ethoxylates—a review. Environ. Int. 28, 215–226. Zwiener, C., Frimmel, F.H., 2003. Short-term tests with a pilot sewage plant and biofilm reactors for the biological degradation of the pharmaceutical compounds clofibric acid, ibuprofen, and diclofenac. Sci. Total Environ. 309 (1–3), 201–211.