Indicator compounds for assessment of wastewater effluent contributions to flow and water quality

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Indicator compounds for assessment of wastewater effluent contributions to flow and water quality Eric R.V. Dickenson a, Shane A. Snyder b, David L. Sedlak c, Jo¨rg E. Drewes a,* a

Advanced Water Technology Center (AQWATEC), Environmental Science and Engineering Division, Colorado School of Mines, Golden, CO 80401, USA b Applied Research and Development Center (ARDC), Water Quality Research and Development Division, Southern Nevada Water Authority, Henderson, NV 89015, USA c Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA

article info

abstract

Article history:

Numerous studies have reported the presence of trace (i.e., ng/L) organic chemicals in

Received 6 March 2010

municipal wastewater effluents, but it is unclear which compounds will be useful to

Received in revised form

evaluate the contribution of effluent to overall river flow or the attenuation processes that

30 October 2010

occur in receiving streams. This paper presents a new approach that uses a suite of

Accepted 9 November 2010

common trace organic chemicals as indicators to assess the degree of impact and atten-

Available online 16 November 2010

uation of trace organic chemicals in receiving streams. The utility of the approach was validated by effluent monitoring at ten wastewater treatment plants and two effluent-

Keywords:

impacted rivers with short retention times (<17 h). A total of 56 compounds were partic-

Indicator

ularly well suited as potential indicators, occurring frequently in effluent samples at

Trace organic chemical

concentrations that were at least five times higher than their limit of quantification.

Wastewater treatment

Monitoring data from two effluent-impacted rivers indicated that biotransformation was

Performance monitoring

not important for these two river stretches, whereas photolysis attenuation was possibly

Pharmaceuticals

important for the shallow river. The application of this approach to receiving waters and

Water reclamation and reuse

water reclamation and reuse systems will allow for more effective allocation of resources in future monitoring programs. ª 2010 Elsevier Ltd. All rights reserved.

1.

Introduction

Drinking water sources that receive treated wastewater discharge or that are augmented in part through potable water reuse can contain trace organic chemicals at concentrations that may have the potential to elicit adverse effects to aquatic life or human health. A 30-year old scoping study published by the United States (U.S.) Environmental Protection Agency in 1980 estimated that about 15 million people in the U.S. were served by surface supplies containing at least 10 percent treated wastewater at low flow conditions and 4 million people use municipal supplies that contain close to 100 percent treated wastewater

during low flow conditions (Swayne et al., 1980). With increasing water demand and dwindling water resources in many communities the proportion of treated wastewater impacted drinking water supplies in the U.S. has likely risen significantly. In this decade, several monitoring campaigns (e.g., Kolpin et al., 2002; Glassmeyer et al., 2005) indicated the presence of trace organic chemicals in U.S. surface waters and groundwaters susceptible to treated wastewater discharge. More recently, Benotti et al. (2009) reported the presence of wastewater-derived chemicals in finished water of 19 U.S. drinking water utilities. These chemicals span a wide range of categories, such as pharmaceutical residues, personal care products, household

* Corresponding author. Tel.: þ1 (303) 273 3401; fax: þ1 (303) 273 3413. E-mail address: [email protected] (J.E. Drewes). 0043-1354/$ e see front matter ª 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2010.11.012

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w a t e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 1 9 9 e1 2 1 2

chemicals, suspected endocrine disrupting compounds, transformation products, and others. Despite the strong interest in these findings, the occurrence of wastewater-derived trace organic compounds at concentrations in the nanogram-perliter (ng/L) range has been reported sporadically over the last 40 years. The recently reported detection of these compounds was driven mainly by the availability of more sensitive analytical instruments. The most important sources for release of trace organic chemicals into surface and groundwater are discharges from municipal wastewater treatment plants (WWTPs), industrial manufacturing processes, leaky sewers, combined sewer overflows, onsite wastewater treatment systems, agricultural practices including confined animal feeding operations (Drewes and Shore, 2001). Generally, the occurrence levels of these trace organic chemicals in drinking water sources primarily depend upon physicochemical properties, their fate in the environment after discharge, and the relative contribution of treated wastewater to the overall flow. However, the degree of treated wastewater impact for the majority of occurrence studies is frequently either not reported or not known. Additional factors affecting occurrence are different usage patterns (e.g., pharmaceutical prescription practices), which can vary with region, per-capita water consumption (resulting in different levels of dilution) and substitution and phase-out programs for specific chemicals. This denotes that the occurrence pattern of currently detected trace organic chemicals is not static. Providing certain chemicals occur at quantifiable concentrations, conservative and nonconservative anthropogenic indicator markers can be used to assess wastewater contamination in receiving waters. Conservative inorganic markers, such as boron (B) isotopes (Vengosh et al., 1994; Bassett et al., 1995) and gadolinium (Gd) (Verplanck et al., 2005), have been successfully used to indicate wastewater impact, but they have their limitations. In order for B isotopes to be applicable to a particular site they need to be well characterized in all relevant water sources and the resulting B isotopic signatures need to be distinguishable from background water sources. Also, the occurrence of Gd is usually associated with and limited to communities with magnetic resonance imaging facilities. Conservative organic markers may provide a more robust alternative, where several studies have proposed select markers to indicate the influence of wastewater into receiving water bodies (Buerge et al., 2003, 2008, 2009; Clara et al., 2004; Fono and Sedlak, 2005; Glassmeyer et al., 2005; Nakada et al., 2008). However, little information is available on the use of frequently occurring nonconservative indicators to indicate the reduction of co-occurring compounds with similar physiochemical and biodegradable characteristics in receiving rivers. These types of indicator compounds are important as they provide a more complete evaluation regarding the attenuation of wastewater-derived chemicals that is not solely due to dilution. However, implementing suitable conservative and nonconservative indicator compounds is currently hindered since a comprehensive identification of unregulated trace organic chemicals that commonly occur in treated wastewater effluents regardless of location is lacking. Therefore, the objective of this study was to identify and verify viable indicator compounds by evaluating the occurrence of the most frequently detected trace organic chemicals occurring in North American conventional secondary- or tertiary-treated

wastewater effluents and to assess the fate and transport of trace organic chemicals by monitoring select indicator compounds in two rivers highly impacted by treated wastewater discharge.

2.

Materials and methods

2.1.

Full-scale monitoring

Ten full-scale wastewater treatment facilities were selected to evaluate the occurrence of trace organic chemicals in secondary, tertiary, or membrane bioreactor treated effluents (Table 1). Biologically treated effluent samples were collected prior to disinfection with exceptions to facilities 2 and 8, where biologically treated effluent samples were collected after chloramine and chlorine application, respectively. Multiple sampling events were performed at some facilities (Table 1). Efforts were made to reduce, if not eliminate, the use of plastics during the sampling process because of the propensity to either cause adsorptive losses of target compounds or leaching of compounds targeted in the study into the sample (i.e., bisphenol A). Only glass or metal collection containers were used during sample collections, and if plastic tubing was employed, well-conditioned tubing was used. Initially, samples were collected directly in a single, cooled 20 L glass container, then split into various sample containers and shipped overnight to participating laboratories. Samples were collected as composites over a short period (2e4 h). Prior to sampling, the normal operation of the plant was confirmed by assuring that operational parameters were within their technical design specifications. Care was also taken not to collect samples within 48 h following a rain event.

2.2.

Receiving river monitoring

The attenuation of select trace organic compounds was assessed at two river sites impacted by treated wastewater discharge. A sampling campaign was conducted at river site 1 during the day of June 21, 2006. This river, which usually is dry and only carries water upstream of the site during flooding conditions, received chlorinated (followed by dechlorination) secondary-treated wastewater (non-nitrified; trickling filter process) from a 150 ML/day plant, which made up 100% of the flow in the river (no flow upstream of the discharge). Downstream water flows were monitored on the day of sampling using USGS stream gauging stations. The average flow on the day of sampling was 1.0 m3/s. The studied river stretch was not influenced by major river tributaries or other treated wastewater outfalls. Synoptic grab sampling occurred downstream of the discharge (8.3 km), which represented an estimated travel time of 6 h based on time studies performed by the USGS using peak flow measurements. During the time of sampling the weather was sunny, clear skies, zero precipitation, and the air temperature ranged from 31.7 to 36.1  C as recorded by the National Weather Service. The river stretch between the discharge and downstream sampling point was shallow, ranging from 10 cm to 35 cm in depth. Site and water quality data at river site 1 are presented in Table 2. River site 1 was characterized by high TOC (14 mg/L), ammonia (20 mg N/L), and phosphate (10 mg/L) concentrations.

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Table 1 e Conventional full-scale wastewater treatment facilities in the U.S. Facility

Capacity

Treatment train

# Sampling events

Facility 1

40 mgd 151 ML/day 6 mgd 23 ML/day 2.5 mgd 9.5 ML/day 20 mgd 76 ML/day 88.5 mgd 335 ML/day 14 mgd 53 ML/day 21 mgd 79 ML/day 15 mgd 57 ML/day 25 gpm 95 L/min 5 mgd 19 ML/day

Primary, secondary (trickling filter; partly nitrifying), disinfection (chloramine) Primary, secondary (activated sludge; non nitrifying), disinfection (chloramine), microfiltration Primary, secondary (activated sludge; partly nitrifying/denitrifying), disinfection (chloramine) Primary, secondary (activated sludge; nitrifying), chemical phosphorus-removal, ultrafiltration, disinfection (ozone) Primary, secondary (activated sludge; nitrifying), tertiary filtration, disinfection (UV irradiation) Primary, secondary (activated sludge; nitrifying), disinfection (chloramine) Primary, secondary (activated sludge; nitrifying), tertiary filtration, disinfection (chloramine) Primary, secondary (activated sludge; nitrifying/denitrifying), tertiary filtration, disinfection (chlorine) Primary, MBRb (activated sludge; nitrifying/denitrifying)

2

MBR (activated sludge; nitrifying/denitrifying), disinfection (UV irradiation)

2

Facility 2 Facility 3 Facility 4 Facility 5 Facility 6 Facility 7 Facility 8 Facility 9a Facility 10

2 1 2 4 1 1 3 2

Primary treatment: mechanical treatment. ML/day e Million liters per day; mgd e million gallons per day. a Pilot-scale system. b Membrane bioreactor.

At river site 2 a sampling campaign was conducted on April 30, 2006. The river sampled at site 2 received a blend of nonnitrified (130 ML/day) and nitrified (375 ML/day) chlorinated (followed by dechlorination) secondary-treated wastewater (activated sludge treatments), which made up 35% of the flow in the river during the time of sampling, since there was an existing upstream flow. The studied river stretch was not influenced by major river tributaries or other treated wastewater outfalls. Water flows were monitored on the day of sampling using USGS downstream gauging stations. The average flow on the day of sampling was 5.7 m3/s. Synoptic and 1 h time-composite sampling occurred at four locations downstream of the WWTP. These locations are representative of approximate travel times of 30 min, 5 h, 12 h, and 17 h downstream from the point of wastewater discharge, as determined by previous tracer studies performed at similar river flow conditions. The approximate travel distances of the river from the point of discharge were 0.8, 8, 19, and 27 km, respectively. During the time of sampling the weather was mostly cloudy or scattered clouds with 0.25 mm of precipitation. The air temperature ranged from 7.2 to 19.4  C as recorded by the National Weather Service. The river stretch between the discharge and downstream sampling points was approximately 1.2 m. Site and water quality data at river site 2 are presented in Table 2. The river at site 2 was characterized by relatively high TOC levels (8 mg/L), but it had lower ammonia (<0.1 mg N/L) and moderate phosphate concentrations (2.5 mg/ L) though it was higher in nitrate levels (3 mg N/L) than the river at site 1.

2.3.

Analytical methods

Multiple methods were used to quantify trace organic chemicals. Liquid chromatography (LC) followed by UV detection was

used for the analysis of total EDTA (Bedsworth and Sedlak, 2001). LC with tandem mass spectrometry (LC/MS-MS) was used for the analysis for a suite of pharmaceutical residues, personal care products, suspected endocrine disrupting compounds and pesticides (Trenholm et al., 2006; Vanderford and Snyder, 2006). Gas chromatography/mass (GC/MS) spectrometry was used for a suite of pharmaceutical residues, pesticides and chlorinated flame retardant compounds (Reddersen and Heberer, 2003; Hoppe-Jones et al., 2010). Gas chromatography/tandem mass (GC/MS-MS) spectrometry was used for pharmaceutical b-blockers (Fono and Sedlak, 2005, Kolodziej et al., 2004) and N-nitrosodimethlyamine (NDMA) (Mitch et al., 2003). Samples were extracted within two weeks and were stored at 4  C until analyses of extracts were completed. Field and laboratory blanks were processed like field samples. Findings from two analytical Round Robin experiments and split samples analyzed during field monitoring efforts indicated that the methods employed during this study were comparable for common analytes (i.e., diclofenac, gemfibrozil, ibuprofen, naproxen, tris[2-chloroethyl]-phosphate) with relative standard deviations (RSDs) of less than 30% (Drewes et al., 2008).

3.

Results and discussion

3.1. Selection of potential indicator compounds from a literature survey Numerous past studies have reported the presence of trace organic chemicals in effluents of North American (U.S. and Canada) conventional wastewater treatment facilities. However, if trace organic chemicals do not occur at concentrations significantly above their detection limits and at high

1.53 1.58 1.57 1.52 N/R N/M 8.5 8.3 8.0 7.9 N/R 2.6 91 91 89 100 65 83 N/M e not measured; N/R e not reported; DO e dissolved oxygen; TOC e total organic carbon; SUVA e ultraviolet absorbance at 254 nm/TOC. a Sample collected at site 4 in Fono et al. (2006) on September 1, 2005 by the USGS. b Sample collected at site 3 in Gross et al. (2004).

2.7 2.7 2.3 2.5 1.47 N/R 3.7 3.2 2.6 3.0 3.8 6.9 990 964 970 1050 618 N/R 0.8 8 19 27 N/R 12 River Site 2 (5.7 m3/s) Downstream location #1 Downstream location #2 Downstream location #3 Downstream location #4 Trinity Rivera (23 m3/s) Santa Ana Riverb (1.4 m3/s)

0.5 5 12 17 264 7.5

7.7 7.8 7.6 7.7 8.4 N/R

14.3 16.2 18.7 18.0 30.2 N/R

7.8 8.9 9.0 7.2 7.5 8.5

0.10 0.10 0.09 0.15 <0.04 N/R

1.21 1.24 14.2 14.0 112 128 10 11 0.7 0.5 17 23 1182 1159 <2 <2 N/M N/M 0 8.3 River Site 1 (1.0 m3/s) River discharge Downstream location

0 6

7.6 7.6

Cond. (uS/cm) DO (mg/L) Distance from WWTP discharge (km)

Travel time from WWTP discharge (h)

pH

Temp. (C)

Ammonia (mg N/L)

Nitrate (mg N/L)

Phosphate (mg/L)

Chloride (mg/L)

TOC (mg/L)

SUVA (L/mg m)

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Sample location

Table 2 e River site information and water quality data at river sites 1 and 2 and the Santa Ana and Trinity Rivers studied by Lin et al. (2006) and Fono et al. (2006), respectively.

1202

frequencies, many of these compounds may not represent good indicator candidates for monitoring efforts. Using these criteria, compound occurrence data was screened and compounds that did not occur at a frequency above 80% or were not present in secondary- or tertiary-treated wastewater at concentrations at least five times higher than their respective limits of quantification were eliminated. Compounds considered during screening are presented in Table SI. Based on this analysis a list of 52 potential indicator compounds was identified in North American wastewater effluents (Table 3). For most compounds, their occurrence in effluent was reported in more than one study and in multiple WWTP effluents, where the median total number of WWTPs was 13. Pharmaceutical residues and fragrance compounds were the dominant types of compounds identified among the compounds targeted in this study. It is noteworthy, that this screening of compounds is biased through the application of analytical methods that targeted compounds that were of interest to the researchers who initiated the study. It is possible that other viable indicator compounds are present, but analytical methods may not exist for these compounds or existing methods have not been applied to measure these compounds in treated wastewater. A successful indicator compound is one that can be used to quantify changes in concentration that occur in receiving waters. However, it is difficult to detect the loss of a compound, if it is initially present at a concentration near the detection limit. Therefore, it is necessary to consider a compound’s concentration relative to the limit of quantification (LOQ). To address this issue, Sedlak et al. (2004) proposed a detection ratio (DR):

DR ¼

½Concentrationmedian ½LOQ

(1)

The detection ratio was calculated for a compound for a given study based on the reported median concentration and the LOQ. However, when the median concentration was not reported or could not be calculated for a given study, the reported average concentration was used in Eq. (1). In this study a detection ratio of 5 was selected to identify potential indicator compounds as this ratio allows attenuation evaluation of a particular compound in excess of 80%. Potential indicator compounds with detection ratio 5 are reported in Table 3. The detection ratios reported in Table 3 are representative average detection ratios across studies. The LOQ was sometimes variable among studies that employed different analytical methods. Therefore, in order to compare detection ratios evenly among studies the median concentrations were normalized by the same LOQ. LOQs employed in Eq. (1) were based upon reported analytical methods that are less than 30 ng/L, which allows for a greater probability of detection of a compound. These LOQs are reported in Table 3 and ranged from 0.25 to 30 ng/L, with the majority of LOQs between 1 and 10 ng/L. The number of WWTPs evaluated for a given study varied, therefore in order to take into account this bias, the weighted-average detection ratio (and standard deviation) that considers the number of WWTPs that was examined per study was calculated and represents the detection ratio reported in Table 3. With the exception of eight compounds, the detection ratio exceeded 10 for most of the compounds (Table 3). Therefore,

Table 3 e Average detection frequencies (DF) and detection ratios (DR) calculated from literature for potential organic indicator compounds in North American treated wastewater effluents. Method detection limit (MDL) and limit of quantification (LOQ) and corresponding analytical method and reference are listed. Compound

Compound category Fragrance PhAC DBP

Isobornyl acetate Hexylcinnamaldehyde Benzophenone

Fragrance Fragrance UV absorber

Terpineol Codeine

Fragrance PhAC

Fluoxetine

PhAC

Musk xylene TDCPP Methyl salicylate Bisphenol A Propylparaben g-Methyl ionine Propranolol Metoprolol Caffeine

Oxybenzone Dibutyl phthalate Acetyl cedrene OTNE, ethanone TCEP

Benzyl acetate Diclofenac

Simonich et al. (2002) Glassmeyer et al. (2005) Sedlak et al. (2005a), Najm and Trussell (2001) Simonich et al. (2002) Simonich et al. (2002) Glassmeyer et al. (2005), Loraine and Pettigrove (2006), Drewes et al. (2009) Simonich et al. (2002) Glassmeyer et al. (2005), Benotti and Brownawell (2007)

Analytical Method

Ref.

12 10 8

100 91 88

n/a n/a 7

5 5 5

n/a n/a 3

n/a n/a n/a

2 15 10

GC/MS LC/MS GC/MS

Simonich et al. (2002) Glassmeyer et al. (2005) Najm and Trussell (2001)

12 12 16

100 100 100

n/a n/a 0

6 7 7

n/a n/a 1

n/a n/a n/a

4 2 25

GC/MS GC/MS LC/MS-MS

Yang and Carlson (2004) Simonich et al. (2002) Trenholm et al. (2008)

12 11

100 84

n/a 6

8 9

n/a 1

n/a n/a

5 15

GC/MS LC/MS

Simonich et al. (2002) Glassmeyer et al. (2005)

5

94

14

10

3

0.19

1

LC/MS-MS

Trenholm et al. (2006)

12 10 12 7 6 12 25

92 100 100 100 83 100 79

n/a n/a n/a n/a n/a n/a 14

10 10 11 14 16 17 19

n/a n/a n/a n/a n/a n/a 6

n/a n/a n/a n/a n/a n/a 0

1 30 4 1 0.25 2 1

GC/MS GC/MS GC/MS LC/MS-MS LC/MS-MS GC/MS GC/MS/MS

Simonich et al. (2002)

18

98

3

20

21

0

10

GCeMS/MS Fono and Sedlak (2005)

15

81

13

21

27

n/a

10

LC/MS-MS

Trenholm et al. (2006)

11

91

8

23

8

0.48

1

LC/MS-MS

Trenholm et al. (2006)

6 12 12 16

100 100 100 94

n/a n/a n/a 9

24 25 28 28

n/a n/a n/a 8

n/a n/a n/a 1.6

25 7 4 10

GC/MS-MS GC/MS GC/MS LC/MS-MS

Simonich et al. (2002) Simonich et al. (2002) Simonich et al. (2002) Trenholm et al. (2006)

12 28

100 75

n/a 29

29 36

n/a 23

n/a 0.14

3 1

GC/MS LC/MS-MS

Simonich et al. (2002) Trenholm et al. (2006)

Simonich et al. (2002) Vanderford and Snyder (2006) Trenholm et al. (2008) Simonich et al. (2002) Fono and Sedlak (2005)

1203

Snyder et al. (2007), Vanderford et al. (2003) Fragrance Simonich et al. (2002) Flame retardant Glassmeyer et al. (2005) Fragrance Simonich et al. (2002) Plasticizer Drewes et al. (2005) Biocide Trenholm et al. (2008) Fragrance Simonich et al. (2002) Beta Blocker Fono et al. (2006), Sedlak et al. (2005b), Fono and Sedlak (2005) Beta Blocker Fono et al. (2006), Sedlak et al. (2005b) Stimulant Glassmeyer et al. (2005), Snyder et al. (2007), Vanderford et al. (2003) UV absorber Snyder et al. (2007), Drewes et al. (2009) Plasticizer Drewes et al. (2009) Fragrance Simonich et al. (2002) Fragrance Simonich et al. (2002) Flame retardant Glassmeyer et al. (2005), Snyder et al. (2007), Vanderford et al. (2003) Fragrance Simonich et al. (2002) PhAC Snyder et al. (2007), Vanderford et al. (2003), Drewes et al. (2002), Miao et al. (2004), Fono et al. (2006), Sedlak et al. (2005b)

Total # Averageb Stand. Averageb Stand. MDL LOQc DR dev. (ng/L) (ng/L) WWTPsa DF (%) dev. (%)

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Hexyl salicylate Diphenhydramine NDMA

Occurrence reference

(continued on next page)

Compound

p-t-Bucinal Musk ketone

Compound category Fragrance Fragrance

Methyl dihydrojasmonate Fragrance Benzyl salicylate Fragrance Ibuprofen Pharmaceutical

Pharmaceutical

Ofloxacin

Pharmaceutical

Sulfapyridine Nonylphenol

Pharmaceutical Surfactant

Dilantin

Pharmaceutical

Clarithromycin Carbamazepine

Pharmaceutical Pharmaceutical

Galaxolide

Fragrance

Primidone Erythromycin

Pharmaceutical Pharmaceutical

Iopromide Naproxen

X-ray contrast agent Pharmaceutical

Indol-3-butyric acid

Plant Hormone

Simonich et al. (2002) Snyder et al. (2007), Simonich et al. (2002) Simonich et al. (2002) Simonich et al. (2002) Snyder et al. (2007), Vanderford et al. (2003), Miao et al. (2004), Fono et al. (2006), Sedlak et al. (2005b) Benotti and Brownawell (2007), Snyder et al. (2007), Vanderford et al. (2003) Miao et al. (2004), Sedlak et al. (2005b) Miao et al. (2004) Drewes et al. (2005), Snyder et al. (1999) Snyder et al. (2007), Vanderford et al. (2003) Miao et al. (2004) Glassmeyer et al. (2005), Benotti and Brownawell (2007), Snyder et al. (2007), Drewes et al. (2002) Glassmeyer et al. (2005), Snyder et al. (2007), Simonich et al. (2002) Drewes et al. (2002) Glassmeyer et al. (2005), Snyder et al. (2007), Miao et al. (2004), Yang and Carlson (2004) Snyder et al. (2007), Vanderford et al. (2003) Snyder et al. (2007), Vanderford et al. (2003), Drewes et al. (2002), Miao et al. (2004), Fono et al. (2006), Sedlak et al. (2005b) Drewes et al. (2009)

Total # Averageb Stand. Averageb Stand. MDL LOQc DR dev. (ng/L) (ng/L) WWTPsa DF (%) dev. (%)

Analytical Method

Ref.

12 13

100 87

n/a 7

41 42

n/a 24

n/a 5.5

1 10

GC/MS GC/MS

Simonich et al. (2002) Simonich et al. (2002)

12 12 28

100 100 78

n/a n/a 21

43 44 49

n/a n/a 30

n/a n/a 0.18

2 2 1

GC/MS GC/MS LC/MS-MS

Simonich et al. (2002) Simonich et al. (2002) Trenholm et al. (2006)

7

100

0

54

21

0.29

1

LC/MS-MS

Trenholm et al. (2006)

15

93

7

67

22

2

n/a

LC/MS/MS

Miao et al. (2004)

8 13

100 100

n/a 0

81 85

n/a 17

1 15

n/a n/a

LC/MS/MS GC/MS

Miao et al. (2004) Drewes et al. (2005)

6

100

0

87

4

0.33

1

LC/MS-MS

Trenholm et al. (2008)

8 21

80 88

n/a 13

87 94

n/a 28

1 n/a

n/a 1

LC/MS/MS LC/MS-MS

Miao et al. (2004) Trenholm et al. (2006)

23

100

0

95

60

5.8

10

GC/MS-MS

Trenholm et al. (2006)

5 24

100 83

n/a 14

115 124

n/a 41

<1 0.22

1 1

GC/MS LC/MS-MS

Drewes et al. (2002) Trenholm et al. (2006)

6

100

0

125

5

0.58

1

LC/MS-MS

Trenholm et al. (2006)

28

92

8

126

120

0.23

1

LC/MS-MS

Trenholm et al. (2006)

6

100

n/a

127

n/a

n/a

1

LC/MS-MS

Trenholm et al. (2008)

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Hydrocodone

Occurrence reference

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Table 3 (continued)

Pharmaceutical

Meprobamate

Pharmaceutical

Triclosan

Biocide

Gemfibrozil

Pharmaceutical

Tonalide (AHTN)

Fragrance

DEET

Insecticide

Triclocarban

Biocide

Sulfamethoxazole

Pharmaceutical

Total EDTA

Chelating agent

Glassmeyer et al. (2005), Benotti and Brownawell (2007), Snyder et al. (2007), Vanderford et al. (2003), Sedlak et al. (2005b), Batt et al. (2006) Snyder et al. (2007), Vanderford et al. (2003) Glassmeyer et al. (2005), Snyder et al. (2007), Loraine and Pettigrove (2006), Drewes et al. (2009), Halden and Paull (2005), McAvoy et al. (2002) Snyder et al. (2007), Vanderford et al. (2003), Miao et al. (2004), Fono et al. (2006), Sedlak et al. (2005b) Glassmeyer et al. (2005), Simonich et al. (2002) Glassmeyer et al. (2005), Snyder et al. (2007), Vanderford et al. (2003), Loraine and Pettigrove (2006), Drewes et al. (2009) Drewes et al. (2009), Halden and Paull (2005) Glassmeyer et al. (2005), Benotti and Brownawell (2007), Snyder et al. (2007), Miao et al. (2004), Sedlak et al. (2005b), Yang and Carlson (2004) Drewes et al. (2003)

26

86

14

241

222

0.19

1

LC/MS-MS

Trenholm et al. (2006)

6

83

10

242

37

0.16

1

LC/MS-MS

Trenholm et al. (2006)

27

98

11

303

328

0.39

1

LC/MS-MS

Trenholm et al. (2006)

28

92

11

308

401

0.17

1

LC/MS-MS

Trenholm et al. (2006)

22

100

0

357

22

n/a

3

GC/MS

Simonich et al. (2002)

23

89

16

380

414

0.44

1

LC/MS-MS

Trenholm et al. (2006)

7

100

0

382

58

n/a

0.25

LC/MS-MS

Trenholm et al. (2008)

32

94

7

426

470

0.22

1

LC/MS-MS

Trenholm et al. (2006)

1

100

n/a

656

n/a

n/a

18

GC/MS

Drewes et al. (2003)

w a t e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 1 9 9 e1 2 1 2

Trimethoprim

WWTP: Wastewater Treatment Plant; n/a: Not Available. a Total number of plants where a compound was measured. Summed across studies. b Weighted-average DF or DR across studies. c When the LOQ was not reported and the MDL was only reported, the MDL was used as the LOQ in Eq. (1) to calculate DR.

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at least 1-log removal can be assessed for these potential indicator compounds. The detection ratio was exceeding 100 for 14 potential indicator compounds, thus 2-log removal can be potentially quantified for these compounds. However, the detection ratio was less than 100 for some of these 14 compounds (i.e., erythromycin, naproxen, trimethoprim, triclosan, gemfibrozil, DEET) for a given study. Therefore, 2-log removal may not always be able to be determined. Conversely, iopromide, meprobamate, tonalide, triclocarban, and sulfamethoxazole always had detection ratios exceeding 100 across all studies and are possibly more suitable indicator compounds to consistently assess 2-log removal across a downstream treatment process or receiving environment. The variability of detection ratios for some compounds (e.g., naproxen, DEET, gemfibrozil, sulfamethoxazole) was considerably high, which could be due to different local usage patterns and/or differing degrees of removals of these compounds during conventional wastewater treatment, but the average DF for these compounds was consistently above 80%. Despite this variability, nearly all of the compounds had detection ratios >5 across studies indicating at least >80% attenuation of these compounds can be quantified. Along with a compound needing to be easily detected it is also necessary for a compound to be frequently detected in order for it to be a viable indicator compound. If it does not frequently occur, then it is not suitable to assess attenuation removal factors. In this study a detection frequency of at least 80% was used to identify potential indicator compounds. Table 3 lists the average detection frequency for identified indicator compounds, which is an average detection frequency across studies. Similar to the average detection ratio the detection frequency is a weighted-average that considers the number of WWTPs that was examined per study. Table 3 lists the detection frequency for potential indicator compounds, where almost all the compounds had a detection frequency exceeding 80%, where the median was 100%. Propranolol, diclofenac, and ibuprofen were exceptions exhibiting detection frequencies between 75 and 80%. However, these compounds were included as they are near the >80% cutoff and higher frequencies were observed in the validation study as discussed in the following section. These results suggest all of the compounds in Table 3 occur frequently in treated wastewater effluent and are potentially suitable indicator compounds.

3.2. Indicator compounds and detection ratios in secondary- or tertiary-treated effluents Ten full-scale conventional wastewater treatment facilities located in the U.S. (Table 1) were selected to validate the occurrence of the proposed indicator compounds (Table 3) in conventionally treated secondary- or tertiary-treated effluents. For this screening effort, 39 trace organic chemicals were selected (Table S2, Supplemental Information). The detection ratios for these trace organic chemicals were averaged across wastewater treatment plants and results are presented in a box and whisker plot in Fig. 1. Note, due to budget constraints not all the compounds were measured at every facility as only selected analytical methods were employed for samples from a given facility. The total number of WWTP effluents evaluated

for the occurrence of trace organic chemicals and the detection frequencies are noted within Fig. 1. Considering the monitoring results from these facilities, detection ratios and frequencies are in agreement with the proposed indicator compounds listed in Table 3. Twenty-nine out of the 39 compounds targeted in Fig. 1 are detected greater than 80% of the time. Detection frequencies are less than 80% for ketoprofen, estriol, estrone, mecoprop, atrazine, and acetaminophen, which confirmed detection frequencies of less than 80% calculated for these compounds reported in previous studies (data not shown). The detection ratio values are greater than five (black horizontal line within Fig. 1) for some of the potential indicator compounds identified in Table 3. Three additional compounds, atenolol, simvastatin hydroxy acid, and TCPP, were identified as potential indicator compounds that were not evaluated during the literature survey but met the requirements to serve as an indicator. Compounds with detection ratio values below 5, such as atrazine, diazepam, estriol, and estrone confirm low detection ratios of <1, 2, and 3, respectively, based on the literature survey (data not shown). Therefore, it is proposed that these compounds would not be suitable indicator compounds for assessing >80% removal. Effluent monitoring from past studies and at ten different wastewater treatment facilities examined in this study confirmed similar occurrence patterns of proposed indicator compounds in North American conventional secondary- and tertiary-treated wastewater effluents regardless of location. However, it is likely that the occurrence of these indicator compounds can vary between different countries due to different usage patterns and water consumption practices. For example, clofibric acid, a breakdown product of a blood lipid regulator, is widely administered in middle European countries but rarely used in the U.S. As a consequence, clofibric acid concentrations in treated wastewater effluents in Switzerland (Tauxe-Wuersch et al., 2005) and Germany (Ternes, 1998) exhibited >50 times higher median concentrations than observed in North America (Drewes et al., 2002; Lishman et al., 2006; Miao et al., 2002) (Table 4). Note, clofibric acid levels are similar between North American and the United Kingdom (Kasprzyk-Hordern et al., 2009). Another important factor to consider in the occurrence pattern of trace organic chemicals in treated wastewater is the strength of treated wastewater. The per-capita indoor water consumption is usually a factor of 2e3 times lower in Europe as compared to the U.S. resulting in higher concentrated wastewater in Europe (American Water Works Association, 2009; Bundesverband der Energie- und Wasserwirtschaft, 2009). For pharmaceutical residues, such as carbamazepine and diclofenac, representing drugs administered both in European countries and North America in similar amounts, this would result in a lower occurrence level in North America. Note, these chemicals are not well attenuated during activated sludge wastewater treatment (Castiglioni et al., 2005; Clara et al., 2005a; Drewes et al., 2008; Joss et al., 2005; Kasprzyk-Hordern et al., 2009; Radjenovic et al., 2009; TauxeWuersch et al., 2005) and therefore, treatment effects on occurrence levels in wastewater treatment effluents can be assumed negligible. Indeed, concentrations of carbamazepine and diclofenac are by a factor of >10 times higher in treated wastewater effluents in Germany (Deng et al., 2003; Ternes, 1998; Ternes et al., 2003), Austria (Clara et al., 2004; Clara et al., 2005b;

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10000

1000

DR

100

10

1 3

4

4

4

4

7

4

7

4

7

10

9

7

3

2

10

7

10

3

10

2

8

10

7

1

10

6

4

5

1

10

4

7

10 10

9

10

8

7

0 100 75 75 75 71 75 100 100 57 10 89 100 67 50 80 100 100 100 80 100 13 40 100 100 100 100 100 80 100 100 100 100 100 100 100 100 88 86

Acetaminophen Atenolol Atorvastatin Atorvastatin (o-Hydroxy) Atorvastatin (p-Hydroxy) Atrazine Bisphenol A Carbamazepine DEET Diazepam Dichlorprop Diclofenac Dilantin Erythromycin-H2O Estriol Estrone Fluoxetine Gemfibrozil Hydrocodone Ibuprofen Iopromide Ketoprofen Mecoprop Meprobamate Metoprolol Naproxen NDMA Norfluoxetine Primidone Propranolol Salicylic acid Simvastatin hydroxy acid Sulfamethoxazole TCEP TCPP TDCPP Total EDTA Triclosan Trimethoprim

0.1

Fig. 1 e Box and whisker plots of the detection ratio of trace organic chemicals in U.S. treated wastewater effluents. The total number of WWTP effluents evaluated and detection frequency (%) for a given compound are listed horizontally and numerically within the graph.

Kreuzinger et al., 2004; Strenn et al., 2004), Switzerland (Kahle et al., 2009; Tauxe-Wuersch et al., 2005), and The United Kingdom (Ashton et al., 2004; Hilton and Thomas, 2003; Kasprzyk-Hordern et al., 2009) as compared to concentrations observed in North American (Benotti and Brownawell, 2007; Drewes et al., 2002; Glassmeyer et al., 2005; Miao et al., 2002; Sedlak et al., 2005a,b; Snyder et al., 2007; Vanderford et al., 2003) effluents (Table 4). Therefore, the occurrence pattern of trace organic chemicals in treated wastewater effluent is country

specific and occurrence studies conducted in one country are not necessarily applicable to other regions of the world. When considering the occurrence of trace organic compounds in treated wastewater effluent disinfection treatment must be considered. In North America, disinfection is commonly applied to secondary- or tertiary-treated wastewater employing disinfection processes including chlorine, chloramine, UV irradiation, and ozone processes. Little removal of trace organic chemicals has been observed, with a few

Table 4 e Carbamazepine, clofibric acid and diclofenac occurrence concentrations and detection frequencies in wastewater treatment effluents in different countries.a Country

Carbamazepine b

Germany Austria Switzerland United Kingdom North America

Clofibric Acid b

Diclofenac

Median conc. (ng/L)

# of Plants

DF (%)

Median conc. (ng/L)

# of Plants

DF (%)

Median conc.b (ng/L)

# of Plants

DF (%)

2100 1123 840 1662 94

30 17 9 2 21

100 100 100 100 88

360 n/a 200 11 4

49 n/a 3 2 8

96 n/a 83 44 58

868 1587 1000 422 37

69 6 3 6 22

100 100 100 90 89

n/a e not available; DF e detection frequency. a Occurrence median concentrations are based on the studies reported in the text. b Average concentration across studies, which were weighted considering the number of WWTPs that was examined for a given study.

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exceptions, during full-scale wastewater chloramination (e.g., 2.6 mg/L residual concentration; 2 h contact time) and UV disinfection processes (e.g., 40 mJ/cm2) (Drewes et al., 2008, 2009). However, the application of chlorine, where free chlorine is present in the aqueous phase, can lead to the selective reduction of some trace organic chemicals (Westerhoff et al., 2005). Chlorine acts as an oxidant or an electrophile, reacting selectively with certain functional groups on organic compounds (Deborde and von Gunten, 2008). Chlorine can selectively react with phenolic compounds, such as acetaminophen, aliphatic amine groups, such as those on propanolol, and amines within heterocyclic structures, such as trimethoprim (Pinkston and Sedlak, 2004; Dodd and Huang 2007). Ozone oxidation can also lead to the oxidation of some trace organic chemicals (Snyder et al., 2006) and Dickenson et al. (2009) identified which indicator compounds, presented in this paper, are reactive or nonreactive during ozone treatment of treated wastewater. Thus, when selecting trace organic chemicals that can serve as indicator compounds, the type and degree of wastewater disinfection needs to be considered. The list of viable indicator compounds identified in North American treated wastewater effluents can be used to tailor monitoring strategies or to assess attenuation in receiving streams. However, the detection criteria of proposed indicator compounds needs to be confirmed for a given facility as local consumption, environmental and treatment practices could potentially affect their occurrence. For example, seasonality (i.e., wet vs. dry) could affect the occurrence of trace organic chemicals, which was not considered in this study. During the wet season, treated wastewater can potentially become more diluted and thus indicator compound levels in effluents are decreased.

3.3. Attenuation of indicator compounds in highly impacted receiving waters The attenuation of select indicator compounds in two wastewater effluent-impacted rivers was assessed. During the time of sampling, river sites 1 and 2 were 35 and 100% impacted, respectively. While many rivers across the U.S. are likely receiving wastewater discharge to much lesser degree, these two study sites provided a better opportunity to monitor attenuation for compounds after wastewater discharge. Concentrations of detectable trace organic chemicals at downstream locations of river sites 1 and 2 are presented in Fig. 2. Most of the studied compounds did not decrease substantially in concentration downstream of the discharges. Interestingly, ibuprofen, gemfibrozil, and naproxen concentrations did not decrease, although the same compounds have been observed to transform during similar travel times in the shallow (w0.3 m) Santa Ana River, California (Lin et al., 2006). The Santa Ana River is also an effluent-dominated river, and Lin et al. (2006) observed attenuation of gemfibrozil, ibuprofen, and naproxen along a 12 km (travel time 7.5 h) stretch with half-lives of 5.4, 3.7, and 2 h, respectively. Lin et al. (2006) performed laboratory microcosm batch experiments that contained sediment from the river, which suggested biotransformation was the principal removal mechanism for ibuprofen and gemfibrozil, whereas biotransformation and photolysis were both important for naproxen removal. A major difference between

river site 1 and Santa Ana River is the wastewater quality applied to the receiving rivers. Site 1 received non-nitrified secondarytreated wastewater, which was typified with high ammonia (w20 mg N/L) and TOC (w14 mg/L) concentrations, where this high oxidant demand attributed to the low observed DO levels (<2 mg/L) in this river. Therefore, aerobic conditions were not maintained and biotransformation of these compounds under aerobic conditions could not occur. On the other hand, the Santa Ana River received nitrified tertiary-treated wastewater, which is characterized by low ammonia concentrations (<0.04 mg N/L) and low TOC concentrations (2.6 mg/L), which allowed for aerobic conditions (DO ¼ 8.5 mg/L) to persist and probably led to the attenuation of these compounds in this shallow river. However, some compounds did decrease in concentration at site 1, such as total EDTA, sulfamethoxazole, diclofenac, trimethoprim, and carbamazepine, which decreased by 47, 33, 27, 20 and 12%, respectively. These removals are probably not due to biological attenuations, since aerobic conditions were not present at site 1, and other more bioamenable compounds were not removed (i.e., ibuprofen, gemfibrozil). Some of these compounds are known to be recalcitrant (i.e., diclofenac, carbamazepine). On the day of sampling at river site 1 the weather was sunny with clear skies, sampling occurred in the summer and the river was shallow with a depth of 10e30 cm, so nearsurface conditions were present. Therefore, these observed attenuations could be due to photolysis where past river field and controlled laboratory-scale studies have reported the degradation of these compounds due to photolysis (Abella´n et al., 2009; Andreozzi et al., 2002, 2003; Boreen et al., 2004; Fono et al., 2006; Kari and Giger, 2002; Tixier et al., 2003; Xue et al., 1995). Ibuprofen, gemfibrozil, and naproxen concentrations also did not decrease in river site 2. This is most likely due to a lower biological activity for this river than in the Santa Ana River. The Santa Ana River is a shallow river allowing close interactions of compounds with the riverbed and subsequent microbial activity. However, river site 2 is a deeper river with a typical depth of 1.2 m, which allows less opportunity for the compounds to interact with the riverbed. Fono et al. (2006) studied the attenuation of gemfibrozil, ibuprofen, and naproxen in a larger (22 m3/s) and deeper river, Trinity River, Texas, which had an average depth of 2 m and an average width of 30 m. They observed attenuation of these compounds along a 500 km stretch (2 week travel time). However, unlike the study in the Santa Ana River by Lin et al. (2006), Fono et al. (2006) observed slower attenuation rates where half-lives of 2.89, 4.6, and 4.2 days were observed. Fono et al. (2006) also performed laboratory-scale microcosm experiments containing only river water (no sediment), and like Lin et al. (2006), these tests supported biotransformation as the important attenuating process for these compounds. Therefore, deeper depths at river site 2 provided less opportunity for the compounds to interact with the riverbed and longer travel times may be required to observe attenuation of these compounds in this river. Past studies have identified individual compounds, including propanolol and caffeine, as suitable anthropogenic markers for treated wastewater contamination in receiving waters (Buerge et al., 2003; Clara et al., 2004; Fono and Sedlak, 2005). However, the results presented here demonstrate that there is a wider range of refractory trace organic chemicals

w a t e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 1 9 9 e1 2 1 2

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Fig. 2 e Concentrations of detectable indicator compounds downstream of wastewater treatment plants at river sites 1 and 2.

(i.e., meprobamate, TCEP, TCPP, carbamazepine), in some cases arguably better (i.e., caffeine is not refractory and can easily contribute to field and laboratory blanks), that can be used to indicate the degree of treated wastewater impact to a receiving body. This is significant as a suite of select indicators can be used as anthropogenic markers, which provides confirmation regarding the degree of treated wastewater contamination. Kahle et al. (2009) successfully employed concentration ratios of multiple marker compounds (e.g., primidone/carbamazepine) to quantify wastewater contamination in Switzerland ground and surface waters. Similarly, indicator concentration ratios between photolabile (i.e., sulfamethoxazole) or biotransformed (i.e., gemfibrozil) indicator compounds and refractory compounds can be used to identify those systems where in-river attenuation is important, such as surface waters with longer hydraulic residence times.

4.

Conclusion

The screening approach developed in this study that utilized detection frequency and ratio as selection criteria and subsequent validation via full-scale monitoring supported the identification of 50þ viable indicator compounds in North American treated wastewater effluents to assess fate and transport of trace organic chemicals of emerging concern for receiving environments. There is a high probability that the identified indicator compounds will occur in effluents of other North American wastewater treatment facilities regardless of location. Recalcitrant, photolabile, and bioamenable indicator compounds were used to assess attenuation at two river sites with short retention times (<17 h). Recalcitrant indicator compounds, such as TCEP, TCPP, and meprobamate, indicate dilution impacts were minimal for the studied river stretches.

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Biotransformed indicator compounds, such as ibuprofen and gemfibrozil, indicate that biotransformation attenuation was likely not important for the two river sites. Photolabile indicator compounds, such as diclofenac and sulfamethoxazole, indicate that photolysis attenuation was possibly a factor at river site 1. The application of indicators can be used to tailor monitoring programs to assess attenuation of similar reactive trace organic chemicals in receiving streams.

Acknowledgements The authors thank the WateReuse Research Foundation (WRF-014-01) for its financial, technical, and administrative assistance in funding and managing the project through which this information was derived. The authors also gratefully acknowledge the financial contributions from the Water Environment Research Foundation (WERF-04-HHE-1CO). The comments and views detailed herein may not necessarily reflect the views of WRF or WERF, its officers, directors, affiliates or agents. The authors are also grateful to the participating utilities for their technical and administrative support. The authors would like to thank Brett Vanderford, Rebecca Trenholm, and Janie Zeigler at SNWA, Mong Hoo Lim and Edward Kolodziej at UC-Berkeley, and John Luna, Christiane Hoppe, Gary Wang and Dean Heil at CSM for their assistance in reviewing literature articles, sample logistics and analysis.

Appendix. Supplementary data Supplementary data associated with this article can be found in the online version, at doi:10.1016/j.watres.2010.11.012.

references

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