U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004–3127

January 2005 Printed on recycled paper

Wastewater Chemicals in Colorado’s Streams and Ground Water

By Lori A. Sprague and William A. Battaglin

Photograph by Jon Nania, U.S. Geological Survey

Figure 1. Chemicals that we use every day 

in homes, industry, and agriculture can enter 

Colorado’s streams and ground water with 

wastewater. 

What are wastewater chemicals?

Chemicals that we use every day 

in homes, industry, and agriculture 

— including detergents, disinfectants, 

fragrances, fire retardants, nonprescription drugs, and pesticides (fig. 1) — can 

enter Colorado’s streams and ground 

water with wastewater. These wastewater 

chemicals can be released to the environment through discharges from industrial 

facilities, animal feed lots, wastewater 

treatment plants (WWTPs), individual 

septic disposal systems (ISDSs), or 

through runoff from land applications in 

agricultural and urban areas.

The human health and environmental effects of wastewater chemicals are 

not well understood, and standards to 

protect human health or aquatic life have 

not been established for most of these 

chemicals. Some chemicals, however, 

such as the detergent degradation product 

nonylphenol and the fragrances AHTN 

and HHCB, have been shown to disrupt reproduction and growth in fish by 

affecting endocrine systems (Thorpe and 

others, 2001; Schreurs and others, 2004). 

Other chemicals, such as the antimicrobial disinfectant triclosan found in many 

liquid soaps, dishwasher powders, and 

plastics, are suspected of increasing the 

antibiotic resistance of bacteria in the 

environment (McMurry and others, 1998) 

or of reducing algae diversity in streams 

(Wilson and others, 2003). Little is 

known about the effects of many other 

individual chemicals or about the 

potential additive or interactive effects of 

mixtures of these chemicals.

Until recently, there have been few 

analytical methods capable of detecting 

these chemicals at the low concentrations found in the environment (Kolpin 

and others, 2002). The U.S. Geological 

Survey (USGS) National Water-Quality 

Laboratory in Denver, Colo., has developed a new analytical method to measure 

concentrations of 62 wastewater chemicals in water (Zaugg and others, 2002). 

Methods were developed to measure 

these particular chemicals because they 

are expected to enter the environment 

through common wastewater pathways, 

are used in significant quantities, may 

have human or environmental health 

implications, and can be accurately 

measured in environmental samples by 

using available technologies (Kolpin and 

others, 2002). 

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Figure 2. The U.S. Geological Survey has 

conducted a small number of studies in 

Colorado examining the occurrence of 

wastewater chemicals in streams in urban 

and forested areas and in ground water 

from domestic and municipal wells.
What do we know about the 

occurrence of these chemicals in 

Colorado?

The USGS, through its National 

Water-Quality Assessment and Toxic 

Substances Hydrology programs and 

in cooperation with local agencies, has 

conducted a small number of studies of 

the occurrence of wastewater chemicals 

in streams and ground water in Colorado 

(fig. 2). This report describes results 

from four types of sites — streams in 

urban areas, streams in forested areas, 

ground water from domestic wells, 

and ground water from municipal 

wells — sampled between August 2001 

and September 2003. Results for individual chemicals are grouped into 

12 major general-use categories, such as 

fragrances and disinfectants (fig. 3), as 

has been done previously (Kolpin and 

others, 2002). For chemicals having multiple uses or sources, a primary use of the 

chemical was chosen for categorization 

purposes. Because sampling was done 

during separate studies, different numbers of samples were collected at each 

type of site. Differences in the number of 

chemicals detected among site types may 

be due to differences in the number of 

samples collected, as well as to differences between site-type characteristics. 

The total number of samples and the 

frequency of detection (in percent) are 

shown along the top of each plot to allow 

easier comparison between site types. All 

data shown in figure 3 are available at 

http://waterdata.usgs.gov/co/nwis/qw/.

Between August 2001 and September 2003, 23 samples were collected at 

15 sites on urban streams: 10 were in the 

South Platte River basin, 4 were in the 

Arkansas River basin, and 1 was in the 

Upper Colorado River basin. The areas 

draining to these sites ranged from moderately to highly urbanized. Some sites 

were located immediately downstream 

from a single large WWTP discharge 

site, whereas others were located farther 

downstream from one or more WWTP 

discharge sites of various sizes. All may 

have been affected at some point in their 

upstream drainage area by ISDS leachate 

or agriculture.

Between October 2002 and September 2003, 17 samples were collected 

at 1 forested stream site. The site was 

located on the Cache la Poudre River, 

upstream from its confluence with the 

North Fork of the Cache la Poudre River. 

Most of the drainage area upstream 

from the site is in either the RooseveltArapahoe National Forest or Rocky 

Mountain National Park. The river is 

used for fishing, whitewater rafting, and 

kayaking, and there are campgrounds 

and isolated private homes with ISDSs 

along the river. There is very little urban 

development and no WWTP discharge 

site upstream from the study site. 

One sample was collected from 

each of 75 domestic wells between 

September 2001 and August 2003 

(Brendle, 2004; Ortiz, 2004a and b). The 

wells were completed in the fracturedrock and sedimentary aquifers in Park 

County, Colo., about 30 miles southwest 

of Denver. Increasing development in 

Park County has led to an increase in the 

number of ISDSs in the region. Depending on the permeability of the aquifer, the 

distance from the ISDS to the well, and 

the rate of water flow in fractures, ISDS 

effluent potentially can reach shallow 

ground water before concentrations of 

contaminants are reduced substantially.

One sample was collected from each 

of 12 municipal wells in Arapahoe, 

Douglas, and Elbert Counties, Colo., 

between March and October 2003. The 

wells were completed in the Dawson 

aquifer, the uppermost aquifer of the 

Denver Basin aquifer system. The northern part of the Dawson aquifer is located 

in the southern metropolitan area of Denver, and along with the three underlying 

aquifers of the Denver Basin, it is used 

primarily for drinking water and lawn 

irrigation (Robson, 1987). In the southern metropolitan area of Denver, where 

ground water is an important source of 

drinking water, urban development could 

make the water supply in the Dawson 

aquifer more vulnerable to contamination. 

The few data currently (2004) available indicate that urban streams were 

the most vulnerable to contamination, 

with one or more wastewater chemicals 

being found in 100 percent of samples 

from urban streams, and with 57 of the 

62 wastewater chemicals being detected 

in at least 1 sample from these sites. Concentrations also tended to be highest in 

urban streams compared to the other site 

types, with total concentrations above 

1 microgram per liter (μg/L or part per 

billion) occurring in 8 of the 12 generaluse categories (antioxidants, detergent 

metabolites, disinfectants, fire retardants, 

fragrances/flavors, nonprescription drugs, 

PAHs, and steroids) and total concentrations above 10 μg/L occurring in 3 of 

the 12 general-use categories (detergent 

metabolites, fire retardants, and nonprescription drugs). 

Samples from the domestic wells generally had a lower number of wastewater 

chemicals detected and at lower concentrations compared to the urban streams 

sampled. However, a wide variety of 

chemicals also were detected (34 of 62) 

in the domestic wells. Total concentrations above 1 μg/L occurred in 7 of the 

12 general-use categories (detergent 

metabolites, disinfectants, fire retardants, 

fragrances/flavors, plasticizers, solvents, 

and steroids).

The forested stream had fewer wastewater chemicals detected (11 of 62) and 

at lower concentrations compared to 

the urban streams and domestic wells 

sampled. Total concentrations above 

1 μg/L occurred in only one general-use 

category (detergent metabolites). 

The municipal wells sampled had the 

fewest wastewater chemicals detected 

(6 of 62) and the lowest concentrations 

measured of the four site types. Total 

concentrations were below 1 μg/L in all 

general-use categories.

No concentrations of individual 

chemicals exceeded currently (2004) 

established drinking-water standards in 

any of the samples; however, no standards have been established for most of 

these chemicals (U.S. Environmental 

Protection Agency, 2004). Concentrations of caffeine, DEET, nonylphenol, 

and triclosan, four of the more commonly 

detected chemicals at each site type, are 

shown in figure 4. The U.S. Environmental Protection Agency is developing aquatic-life criteria for nonylphenol 

because of its potential for endocrine 

disruption (U.S. Environmental Protection Agency, 2003), and triclosan is of 

concern because it may increase the antibiotic resistance of bacteria in the environment. Both chemicals were frequently 

detected in urban stream samples; triclosan also was present in samples from 

domestic and municipal wells.

Wastewater chemicals were detected 

more frequently and generally at higher 

concentrations in samples from urban 

streams and domestic wells than in 

samples from the forested stream and 

municipal wells. The results indicate 
Antioxidants Detergent

metabolites

Disinfectants Fire

retardants

Fragrances/

Flavors

Insect

repellants

Nonprescription

drugs

PAHs Pesticides Plasticizers Solvents Steroids

0.001

0.01

0.1

1

10

100

TION, IN MICROGRAMS PER LITER CONCENTRA

17

0

75

1

12

0

2326

17

6

7512

12

0

23

57

1712

7512

1217

2357

17

0

7515

12

8

2387

17

18

7513

12

0

23

91

1741

75

8

12

0

2383

17

6

75

1

12

8

2374

17

0

75

7

12

0

2339

17

0

75

1

12

8

2374

17

6

7525

12

0

2365

17

6

7517

12

8

23

17

17

0

75

1

12

0

23

43

BromacilCarbarylChlorpyrifosDiazinonDichlorvosMetalaxylMetolachlorPentachlorophenolPrometon

3-Methyl-1H-indole (skatol)AcetophenoneAcetyl-hexamethyl-tetrahydronaphthalene (AHTN)BenzophenoneCamphord-LimoneneHexadydrohexamethyl-cyclopentabenzopyran (HHCB)IndoleIsoquinolineIsoborneolMenthol

1,4-Dichlorobenzene

Bromoform

para-Cresol

Triclosan

4-Cumylphenol4-n-Octylphenol4-tert-OctylphenolNonylphenol, diethoxy- (total)Octylphenol, diethoxyOctylphenol, monoethoxypara-Nonylphenol (total)

CaffeineCotinineMethyl salicylate

N,N-diethyl-meta-toluamide (DEET)

1-Methylnaphthalene2,6-Dimethylnaphthalene2-MethylnaphthaleneAnthraceneAnthraquinoneBenzo[a]pyreneCarbazoleFluorantheneNaphthalenePhenanthrenePyrene

3-tert-Butyl-4-hydroxy anisole (BHA)5-Methyl-1H-benzotriazole

Tri(2-butoxyethyl)phosphate

Tri(2-chloroethyl)phosphateTri(dichlorisopropyl)phosphateTributyl phosphate

3-beta-Coprostanol

beta-Sitosterolbeta-Stigmastanol

Cholesterol

Bisphenol A

Triethyl citrate (ethyl citrate)

Triphenyl phosphate

IsophoroneIsopropylbenzene (cumene)Tetrachloroethylene

EXPLANATION

17

12

Urban stream Forested stream

Domestic wellMunicipal well

Total number of samplesPercentage of total

 samples with detected

 concentrations within the site-type category

Figure 3. A new analytical method developed by the U.S. Geological Survey measures concentrations of 62 wastewater chemicals in water. Measurable concentrations of one or more of these wastewater chemicals were found in streams in urban and forested areas and in domestic and municipal wells. 
Figure 4. Caffeine, DEET, nonylphenol, and triclosan were four of the 

more commonly detected chemicals 

at each site type. The U.S. Environmental Protection Agency is 

developing aquatic-life criteria for 

nonylphenol because of its potential 

for endocrine disruption, and triclosan is of concern because it may 

increase the antibiotic resistance of 

bacteria in the environment. 

Urban stream

Forested stream

Domestic well

Municipal well

0.001

0.01

0.1

1

10

100

CONCENTRATION, IN MICROGRAMS PER LITER

23

83

23

17

23

52

23

65

75

8

75

9

75

3

75

1

17

6

17

41

17

0

17

0

12

0

12

0

12

8

12

EXPLANATION 8

17

6

Caffeine DEET Nonylphenol Triclosan

Total number of samples

Percentage of total samples with

 detected concentrations within

 the site-type category

that urban streams and domestic wells in 

Colorado may be vulnerable to contamination by wastewater chemicals. However, the detection of low concentrations 

of wastewater chemicals in the forested 

stream and deeper municipal wells indicates that these chemicals can be found 

in streams or ground water even in areas 

where there are no obvious sources of 

waste contamination nearby. 

Where do we go from here?

Although data are available from only 

a limited number of sites in Colorado at 

this time, these results indicate that mixtures of wastewater chemicals are present 

at low concentrations at numerous, and 

sometimes unexpected, locations in the 

State. Other USGS studies have found 

hormones, antibiotics, and prescription 

drugs in urban streams receiving WWTP 

effluent across the Nation, including parts 

of the South Platte River (Kolpin and 

others, 2002; Barnes and others, 2002). 

The laboratory methods for measuring 

hormones, antibiotics, and prescription 

drugs in water are being developed and 

are nearing approval for general use by 

the USGS. Laboratory methods for the 

detection of wastewater chemicals in biosolids — solid or semi-solid residue generated during the treatment of domestic 

sewage and recycled as surface-applied 

fertilizer — also are being developed by 

the USGS. 

For more than 100 years, the USGS 

has been successfully partnering with 

State and local agencies to fund waterresources studies through the Cooperative 

Water Program. These initial findings 

on wastewater chemicals in Colorado’s 

streams and ground water, along with the 

new analytical methods being developed 

by the USGS, provide a starting point for 

further investigation into the occurrence, 

fate, and environmental effects of wastewater chemicals in Colorado and across 

the Nation. 

References cited

Barnes, K.K., Kolpin, D.W., Meyer, M.T., 

Thurman, E.M., Furlong, E.T., Zaugg, S.D., 

and Barber, L.B., 2002, Water-quality data 

for pharmaceuticals, hormones, and other 

organic wastewater contaminants in U.S. 

streams, 1999–2000: U.S. Geological Survey Open-File Report 02–94, 7 p.

Brendle, D.L., 2004, Potential effects of 

individual sewage disposal system density 

on ground-water quality in the fracturedrock aquifer in the vicinity of Bailey, Park 

County, Colorado, 2001–2002: U.S. Geological Survey Fact Sheet 2004–3009, 5 p.

Kolpin, D.W., Furlong, E.T., Meyer, M.T., 

Thurman, E.M., Zaugg, S.D., Barber, L.B., 

and Buxton, H.T., 2002, Pharmaceuticals, 

hormones, and other organic wastewater 

contaminants in U.S. streams, 1999–2000 

— A national reconnaissance: Environmental Science and Technology, v. 36, no. 6, 

p. 1202–1211.

McMurry, L.M., Oethinger, M., and Levy, 

S.B., 1998, Over-expression of marA, soxS, 

or acrAB produces resistance to triclosan in 

laboratory and clinical strains of Escherichia coli: FEMS Microbiology Letters, 

v. 166, no. 2, p. 305–309.

Ortiz, R.F., 2004a, Ground-water quality 

of alluvial and sedimentary-rock aquifers in the vicinity of Fairplay and Alma, 

Park County, Colorado, September–October 

2002: U.S. Geological Survey Fact Sheet 

2004–3065, 6 p.

Ortiz, R.F., 2004b, Ground-water quality 

of granitic- and volcanic-rock aquifers 

in southeastern Park County, Colorado, 

July–August 2003: U.S. Geological Survey 

Fact Sheet 2004–3066, 6 p.

Robson, S.G., 1987, Bedrock aquifers in the 

Denver Basin, Colorado — A quantitative 

water resources appraisal: U.S. Geological 

Survey Professional Paper 1257, 73 p.

Schreurs, R.M., Legler, J., Artola-Garicano, 

E., Sinnige, T.L., Lanser, P.H., Seinen, W., 

and Van Der Burg, B., 2004, In vitro and 

in vivo antiestrogenic effects of polycyclic 

musks in zebrafish: Environmental Science 

and Technology, v. 38, no. 4, p. 997–1002. 

Thorpe, K.L., Hutchinson, T.H., Hetheridge, 

M.J., Scholze, M., Sumpter, J.P., and 

Tyler, C.R., 2001, Assessing the biological 

potency of binary mixtures of environmental estrogens using vitellogenin induction 

in juvenile rainbow trout (Oncorhynchus 

mykiss): Environmental Science and Technology, v. 35, no. 12, p. 2476–2481.

U.S. Environmental Protection Agency, 

2004, 2004 edition of the drinking water 

standards and health advisories: U.S. 

Environmental Protection Agency Report 

822–R–04–005, 13 p.

U.S. Environmental Protection Agency, 

2003, Ambient aquatic life water quality criteria for nonlyphenol — draft: U.S. 

Environmental Protection Agency Report 

822–R–03–029, 71 p. 

Wilson, B.A., Smith, V.H., Denoyelles, 

F., Larive, C.K., 2003, Effects of three 

pharmaceutical and personal care products 

on natural freshwater algal assemblages: 

Environmental Science and Technology, 

v. 37, no. 9, p. 1713–1719.

Zaugg, S.D., Smith, S.G., Schroeder, M.P., 

Barber, L.B., and Burkhardt, M.R., 2002, 

Methods of analysis by the U.S. Geological 

Survey National Water-Quality Laboratory — Determination of wastewater 

compounds by polystyrene-divinylbenzene 

solid-phase extraction and capillary-column 

gas chromatography/mass spectrometry: 

U.S. Geological Survey Water-Resources 

Investigations Report 01–4186, 37 p.

 For more information about wastewater studies in Colorado, please 

contact:

District Chief

Water Resources Discipline

U.S. Geological Survey

P.O. Box 25046, MS 415

Lakewood, CO 80225

303-236-4882

http://co.water.usgs.gov