Prepared in cooperation with the Massachusetts Department of Environmental Protection

Pharmaceutical Compounds in Merrimack River 

Water Used for Public Supply, Lowell,

Massachusetts, 2008–09

Scientific Investigations Report 2011–5192

U.S. Department of the Interior

U.S. Geological Survey
Cover. The Pawtucket Falls Dam at Lowell, Massachusetts (Photograph taken December 17, 2010).
Pharmaceutical Compounds in Merrimack River

Water Used for Public Supply, Lowell,

Massachusetts, 2008–09

By Andrew J. Massey and Marcus C. Waldron

Prepared in cooperation with the 

Massachusetts Department of Environmental Protection

Scientific Investigations Report 2011–5192

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Massey, A.J., and Waldron, M.C., 2011, Pharmaceutical compounds in Merrimack River water used for public supply, 

Lowell, Massachusetts, 2008–09: U.S. Geological Survey Scientific Investigations Report 2011–5192, 14 p. 

(Also available online at http://pubs.usgs.gov/sir/2011/5192.)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Hydrologic Setting of the Merrimack River Drinking-Water Source ...........................................2

Sources of Contamination...................................................................................................................4

Drinking-Water Withdrawals and Distribution in the Watershed ................................................5

Sample Collection and Analysis..................................................................................................................5

Site Selection and Field-Data Collection ..........................................................................................5

Sample Processing and Laboratory Analysis ..................................................................................5

Quality of Finished Water .............................................................................................................................6

Quality-Assurance and Quality-Control Samples............................................................................6

Pharmaceuticals and Water-Quality Constituents in Merrimack River Source Water ............8

Effects of Treatment on Pharmaceutical Compounds in Merrimack River Source Water.....11

Summary........................................................................................................................................................12

References Cited..........................................................................................................................................12

Figures

1. Map showing the Merrimack River watershed in New Hampshire and 

Massachusetts and the location of the study area on the Merrimack River near 

Lowell, Massachusetts................................................................................................................3

2. Graph showing daily mean river flow at the U.S. Geological Survey streamgage 

on the Merrimack River below the confluence with the Concord River at Lowell, 

Massachusetts, for January 2008 through July 2009, compared with historical mean 

daily river flows for the period June 1923 through September 2009, and times when 

samples were collected for chemical analysis .......................................................................8

3. Photograph showing kayakers paddling on the Merrimack River near Lowell, 

Massachusetts, June 2009........................................................................................................11

Tables

1. Human-health pharmaceutical compounds measured in raw and finished water from 

the Merrimack River at the Lowell Regional Water Utility, Massachusetts, 2008–09.......2

2. Concentrations of pharmaceutical analytes in quality-control samples and ranges of 

percent recoveries of known concentrations of compounds added to samples ..............7

3. Analytical results for human-health pharmaceuticals measured in raw source water 

and finished drinking water at the Lowell Regional Water Utility, April 2008–

May 2009 ........................................................................................................................................9

4. Physical characteristics and bacterial concentrations in samples of raw source 

water and finished drinking water collected monthly at the Lowell Regional Water 

Utility, April 16, 2008, through June 17, 2009...........................................................................10
iv

Conversion Factors, Datum, and Acronyms

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2)

Volume

gallon (gal) 3.785 Liter (L)

million gallons (Mgal) 3,785 cubic meter (m3

)

cubic foot (ft3

) 0.02832 cubic meter (m3)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Mass

ounce, avoirdupois (oz) 28.35 gram (g)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F–32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
v

Acronyms

CFU colony-forming units

CSO combined sewer overflow

CSS combined sewer system

CWA Clean Water Act

DWTP drining-water treatment plant

LRWU Lowell Regional Water Utility

MassDEP Massachusetts Department of Environmental Conservation

NAWQA National Water-Quality Assessment

NPDES National Pollution Discharge Elimination System

OWC organic wastewater contaminants

QA quality assurance

QC quality control

RL reporting level

SWQA Source-Water Quality Assessment

USGS U.S. Geological Survey

WWTP wastewater-treatment plant

Pharmaceutical Compounds in Merrimack River Water 

Used for Public Supply, Lowell, Massachusetts, 2008–09

By Andrew J. Massey and Marcus C. Waldron

Abstract

This report presents results of a study conducted by the 

U.S. Geological Survey (USGS), in cooperation with the 

Massachusetts Department of Environmental Protection, to 

determine the occurrence of 14 commonly used human-health 

pharmaceutical compounds and fecal-indicator bacteria in 

Merrimack River water used as a drinking-water source by 

135,000 residents in eastern Massachusetts. The study was 

designed to complement the USGS National Water-Quality 

Assessment Program’s Source Water-Quality Assessment, 

which identifies patterns of occurrence of 280 primarily 

unregulated organic wastewater contaminants in source water 

used by community water systems and determines whether 

these patterns also occur in treated drinking water prior to 

distribution. The study involved periodic collection and 

analysis of raw Merrimack River water and treated drinking 

water over the course of 1 year. Water samples were collected 

periodically without regard to flow regime or antecedent 

weather conditions at the Lowell Regional Water Utility’s 

Merrimack River intake upstream from Lowell, Mass. The 

same parcel of water was then sampled as finished water 

following treatment.

Despite the presence of many potential sources of contamination in the drinking-water source area, only 2 of the 14 

pharmaceutical analytes were detected at reportable concentrations in the source-water samples, and these occurred in only 

one set of periodic samples. Acetaminophen, a nonprescription 

analgesic, and caffeine were detected in the September sourcewater samples at concentrations of 0.084 and 0.068 micrograms per liter, respectively. Three other compounds—carbamazepine, an antiepileptic; cotinine, a metabolite of nicotine; 

and diphenhydramine, a nonprescription antihistamine—were 

detected in source-water samples, but at concentrations too 

low to be reliably quantified. None of the 14 pharmaceuticals 

was found in the finished water at a reportable concentration, 

defined as two times the long-term detection limit used by the 

analytical laboratory.

In addition to the pharmaceutical analyses, measurements 

of fecal-indicator bacteria (Escherichia coli) concentrations 

and several physical characteristics were made on all sourcewater samples. Values for these constituents were consistently within State standards. It is possible that the monthly 

sampling schedule missed hydrologic events that would have 

transported greater concentrations of sewage contaminants to 

the sampling site, or that the large flow volume of the river at 

the study site effectively diluted the contaminant signal, but 

it is also likely that recent efforts to separate stormwater- and 

wastewater-discharge systems in the reaches upstream from 

the Lowell Regional Water Utility have greatly reduced the 

potential for sewage contamination at the intake.

Introduction

In the United States and elsewhere, reports of the occurrence and distribution of organic wastewater contaminants 

(OWCs), including antibiotics, pharmaceuticals, natural and 

synthetic hormones, and industrial and household products 

(for example, pesticides, flame retardants, detergent metabolites, antioxidants, and disinfectants) in drinking-water supplies have become commonplace (Barnes and others, 2008; 

Focazio and others, 2008). A U.S. Geological Survey (USGS) 

national survey reported the presence of at least one of these 

compounds in 80 percent of 139 streams sampled in 1999–

2000 (Kolpin and others, 2002). In general, concentrations 

of OWCs detected in the USGS survey were less than 1 part 

per billion, but 75 percent of streams had more than 1 compound, and 34 percent had 10 or more. The health effects of 

exposure to low concentrations and complex mixtures of these 

compounds are largely unknown. Human or ecological health 

standards or criteria have been established for only a very 

small number of OWCs.

In response to the need for more detailed information 

on the occurrence and distribution of these compounds in the 

Nation’s drinking-water supplies, the USGS initiated a Source 

Water-Quality Assessment (SWQA) as part of its National 

Water-Quality Assessment (NAWQA) Program. The goal of 

the SWQA is to characterize the quality of selected rivers 

and aquifers used as a source of supply to community water 

systems throughout the United States (Delzer and Hamilton, 

2007). Surface-water assessments consist of sampling at the 

intakes of surface-water supplies and resampling of the same 

water after passage through the drinking-water treatment process. Sampling is conducted monthly to account for seasonal 
2 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

variability, and additional source and finished-water sample 

pairs are collected during hydrologic events when conditions 

are changing rapidly and contaminant concentrations are 

expected to be elevated. For groundwater assessments, samples from high-production wells supplying community water 

systems and the associated finished water are collected as 

described in Carter and others (2010). Source-water samples 

are analyzed for the fecal-indicator bacterium 

Escherichia coli (E. coli), and all samples are analyzed for 

280 OWCs, including (1) disinfection byproducts; (2) fumigant-related compounds; (3) fungicides; (4) gasoline hydrocarbons, oxygenates, and oxygenate degradates; (5) herbicides 

and herbicide degradates; (6) insecticides and insecticide 

degradates; (7) manufacturing additives; (8) organic synthesis compounds; (9) pavement- and combustion-derived 

compounds; (10) personal-care and domestic-use products; 

(11) plant- or animal-derived biochemicals; (12) refrigerants 

and propellants; and (13) solvents. 

This report describes the occurrence of 14 commonly 

used prescription and nonprescription pharmaceutical 

compounds in source water from the Merrimack River in 

northeastern Massachusetts and in the same water after 

treatment at the Lowell Regional Water Utility (LRWU). 

The LRWU community water system provides treated 

drinking water for more than 135,000 residents, businesses 

and other customers in the communities of Lowell, Dracut, 

Tyngsborough, and Chelmsford, Mass., and typically produces 

about 4.7 billion gallons of drinking water annually (The City 

of Lowell, 2010). The Merrimack River and the LRWU were 

sampled in 2008–09 as part of the USGS SWQA. However, 

because pharmaceuticals were not included in the original 

SWQA analyte list, they were added to the Merrimack River 

assessment through a cooperative agreement between the 

USGS and the Massachusetts Department of Environmental 

Protection. Table 1 provides a list of the compounds together 

with their Chemical Abstracts Service (CAS) Registry 

numbers and primary uses.

Water samples were collected periodically from April 

2008 through June 2009 and included 12 source-water 

samples paired with 12 finished-water samples, plus several 

quality-assurance (QA) samples. Measurements of several 

physical characteristics were recorded for the water samples, 

and additional source-water samples were collected for determination of concentrations of E. coli. Analytical results for 

the 280 SWQA target-analyte-list compounds are published 

separately in Carter and others (2010).

Hydrologic Setting of the Merrimack River 

Drinking-Water Source

The Merrimack River watershed is the fourth largest in 

New England with a drainage area of 5,010 square miles 

(mi2

) about one quarter of this area is in Massachusetts 

(fig. 1). The headwaters of the Merrimack River originate 

more than 175 miles (mi) from the mouth in alpine and 

subalpine streams on the western and southern aspects of the 

White Mountain section of the New England physiographic 

province in central New Hampshire. The main stem of the 

Merrimack River begins south of the White Mountain National 

Forest at the confluence of the Pemigewasset River and the 

Winnipesaukee River. From this confluence, the river flows 

115 mi through the uplands of south-central and southern 

New Hampshire into Massachusetts. In Massachusetts the 

river arcs to the northeast, flowing roughly parallel to the New 

Hampshire border and then draining to the Atlantic Ocean at 

Newburyport, Mass. (fig. 1).

The main sources of river flow are precipitation and 

snowmelt totaling about 45 inches (in.) per year; greater 

amounts (up to 70 in.) of annual precipitation fall at headwater 

altitudes. Groundwater is also a very important component 

of the Merrimack River flow. Annual precipitation recharges 

groundwater, which, in turn, contributes up to 60 percent of 

annual river flow (New England River Basins Commission, 

1978) through permeable sand and gravel aquifers along the 

river and its tributaries. The Merrimack River watershed is 

geographically diverse and ranges from steep granite and 

gneiss alpine summits in the north to the relatively flat coastal 

basin near the Atlantic coast in northeastern Massachusetts. 

The final 22-mi reach of the Merrimack River, downstream 

from Haverhill, Mass., is tidally influenced. Between the 

White Mountains and Atlantic Ocean, the Merrimack River 

Valley widens, and the river and its tributaries provide a level 

flood plain, which is used for varied agricultural production.

Table 1. Human-health pharmaceutical compounds measured 

in raw and finished water from the Merrimack River at the Lowell 

Regional Water Utility, Massachusetts, 2008–09.

Compound name

Chemical 

Abstracts 

Service Registry 

number

Primary use

1,7-Dimethylxanthine 611-59-6 Caffeine metabolite

Acetaminophen 103-90-2 Antipyretic

Albuterol (Salbutamol) 18559-94-9 Antiasthmatic

Caffeine 58-08-2 Stimulant

Carbamazepine 298-46-4 Antiepileptic

Codeine 76-57-3 Analgesic

Cotinine 486-56-6 Nicotine metabolite

Dehydronifedipine 67035-22-7 Antianginal

Diltiazem 42399-41-7 Antihypertensive

Diphenhydramine 147-24-0 Antihistamine

Sulfamethoxazole 723-46-6 Antibiotic

Thiabendazole 148-79-8 Antifungal, antihelmintic

Trimethoprim 738-70-5 Antibiotic

Warfarin 81-81-2 Anticoagulant
Introduction 3

Figure 1. Map showing t he Merrimack River watershed in New Hampshire and Massachusetts and the location of the study area on 

the Merrimack River near Lowell, Massachusetts.

Lake Winnipesaukee

Atlantic Ocean

Lawrence

Haverhill

Concord

Manchester

Nashua

Lowell

Boston

Newburyport

Merrimack R vi er

Nashua River

Co ncord River

Contoocook

River

Suncook

River

Squam

Lake

Newfound Lake

Pemigewasset River

Base from U.S. Geological Survey digital data,

Albers Conic Equal-Area Projection, Central Meridan: -71°00'00",

1st Standard Parallel: 29°30'00", 2nd Standard Parallel: 45°30'00"

Latitude of Origin: 23°00'00", Horizontal Datum: NAD 27

Merrimack River

watershed

White Mountain

New England Upland

Seaboard Lowland

Physiographic sections

EXPLANATION

Cities

Merrimack River watershed

72° 71° 70°

44°

43°

Chelmsford

Tyngsborough Dracut

0 10 20 MILES

0 20 KILOMETERS 10

NEW HAMPSHIRE

VERMONT

MASSACHUSETTS

MAINE

MAINE

NEW HAMPSHIRE

VERMONT

MASSACHUSETTS

CONNECTICUT

RHODE

ISLAND

Lawrence

Haverhill

Nashua

Lowell

Boston

Newburyport

N ashua

River

Concord

River

Chelmsford

Tyngsborough Dracut

0 10 MILES

0 10 KILOMETERS

5

5

Watershed boundary
4 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

Sources of Contamination

Land use in the Merrimack River watershed ranges from 

undeveloped State lands—National Forest and wetlands—

to farmland and agriculture, and from small rural towns to 

relatively large industrial cities, including Manchester and 

Nashua, N.H., and Lowell and Lawrence, Mass. Most population centers developed along rivers that powered early textile 

and industrial mills. These modern cities that have developed 

from the early mill towns require centralized drinking-water 

and wastewater-treatment systems to maintain sanitary conditions and safe, reliable drinking water. The wastewater generally discharges to the river at local outfalls. In 1990, about half 

(48 percent) of New Hampshire’s 1.1 million residents were 

connected to a municipal sewer system (Medalie, 1996). In 

rural unsewered areas, onsite septic systems are typically used 

for the disposal of residential wastewater. 

The Merrimack River receives treated sewage effluent 

in the form of point-source return flows from 46 wastewatertreatment plants (WWTP) permitted to discharge to the main 

stem and tributaries, including the three largest municipal 

WWTP in New Hampshire. Of the total return flows from 

municipal facilities in New Hampshire, 50 million gallons per 

day (Mgal/d), or 60 percent, discharges to surface water in 

the Merrimack River Basin. There are also potential sources 

of contamination from municipal wastewater disposal into 

the Massachusetts reach of the Merrimack River. Municipal 

WWTPs in the Nashua River Basin contribute an additional 

22.5 Mgal/d of treated return flow upstream from the LRWU 

drinking-water intake. Another 57.3 Mgal/d of wastewater 

returns to streams in the Merrimack River Basin downstream 

from the LRWU intake (Medalie, 1996). 

Point-source wastewater-effluent outfalls present a considerable potential source of contamination to the Merrimack 

River drinking-water supply; however, these point sources 

are highly regulated through the National Pollution Discharge 

Elimination System (NPDES), which includes effluent standards and requires that wastewater-treatment technologies be 

developed to protect the aquatic environment and minimize 

risks to human health. These standards have been particularly 

important in reducing bacteria and nutrients that once resulted 

in unsanitary conditions and decreased ecological health in the 

receiving waters near large population centers. The treatment 

process, however, was not designed to remove the entire range 

of anthropogenic materials in the waste stream. Additionally, 

many anthropogenic chemicals in the environment remain 

unregulated and, in general, their collective toxicity is poorly 

understood.

The NPDES, authorized by the Clean Water Act (CWA) 

in 1972 (http://cfpub.epa.gov/npdes/cwa.cfm?program_id=6) 

imposed statutory requirements including industry-wide 

technology-based standards for permitted discharges of treated 

effluent to receiving surface waters. Prior to the establishment 

of the NPDES, it was common for raw sewage to be dumped 

directly into the environment, and many sewage plants performed only primary treatment of wastewater prior to release. 

Primary treatment is the process of allowing solids to settle 

out of the waste stream prior to discharge, but the method is 

usually only about 30 to 60 percent effective at removing suspended solids. Secondary treatment follows primary treatment 

and is designed to remove organic matter through biological 

processes that result in the settling and separation of organicrich sludge from the clearer supernatant. Modern wastewatertreatment technologies also typically include a final disinfection process (irradiation by ultraviolet light or chlorination, for 

example) to kill any remaining bacteria or other pathogens. 

Secondary treatment at the Nashua, N.H., WWTP has been 

online since October 1989 (Mario Leclerc, Superintendent, 

Nashua Wastewater Treatment Facility, written commun., 

2010). Similar technologies are used at the Manchester, N.H., 

WWTP, from which the average daily discharge of treated 

effluent is about 25 Mgal/d.

Combined sewer systems (CSS), in which sewage and 

stormwater are conveyed to a treatment plant through a 

single pipe, may also affect water quality in the Merrimack 

Basin. CSSs may become overwhelmed during heavy rainfall 

events, causing a combined sewer overflow (CSO). CSOs 

may convey untreated domestic, commercial, and industrial 

wastes along with stormwater runoff into receiving waters 

such as the Merrimack River main stem. Major efforts 

have been underway since the 1990s to address CSSs in 

New Hampshire. Since 2003, four of the six cities in New 

Hampshire with CSSs have successfully separated their 

stormwater and wastewater systems. Projects in Nashua and 

Manchester have successfully eliminated some CSSs, and 

more projects are planned or proposed to correct the remaining 

CSSs, where CSOs still occur during heavy precipitation 

(Mucciarone, 2010). In Manchester, N.H., heavy rainfall 

causes approximately 44 CSOs in an average year (Fredrick J. 

McNeill, city of Manchester, written commun., 2010). On an 

annual basis, CSOs may contribute smaller amounts of fecal 

coliform and E. coli bacteria to the river system than other 

nonpoint sources to the Merrimack River; simulation results 

attribute 19 and 8 percent, respectively, of the annual loads of 

these contaminants to CSOs (Camp Dresser & McKee, Inc., 

2004). On a daily or weekly basis, however, CSOs may be the 

main source of these contaminants to downstream sections 

of the river. In fact, procedures requiring WWTP operators to 

inform downstream water users of CSOs or other unplanned 

discharge events are in place so that adjustments may be made 

to drinking-water treatment processes in a timely manner. 

Recreational activities involving human contact with affected 

surface waters are strongly discouraged during CSO events.

Another potential concern regarding wastewater discharged to receiving waters is the persistence of certain 

pharmaceutical compounds in the environment after disposal. 

Recent research has shown that many pharmaceutical compounds and other OWCs pass unaffected through wastewater 

treatment and may persist in surface water and groundwater 

at distance from the sources (Barnes and others, 2008; Kolpin 

and others, 2002). In rural areas where household wastewater is treated with onsite septic systems, groundwater flow to 
Sample Collection and Analysis 5

gaining streams downgradient from residential development 

may contribute OWCs to surface-water or nearby groundwater 

sources. These and other nonpoint, mixed-use areas have been 

implicated as potential sources of low-level OWCs in drinking 

water (Brown and Trombley, 2009). Other potential sources 

of contamination include manufacturing plants, hospitals, and 

confined agricultural feeding operations. Although WWTP 

effluents are only one potential source, human and animal 

wastewater effluent streams are among the most important 

sources of the majority of these compounds in the aquatic 

environment (Focazio and others, 2008). 

Organic wastewater contaminants often originate from 

municipal wastewater discharge because many of them are 

not completely removed during wastewater treatment (Benotti 

and others, 2009). Runoff from chemically treated agricultural 

fields and concentrated domestic animal-feeding operations, 

groundwater inflow containing landfill leachates, and inflows 

from other nonpoint sources in urban areas may also contribute these contaminants to the environment (Barnes and others, 

2004). Furthermore, some of these anthropogenic compounds 

persist through drinking-water treatment processes that were 

not designed to remove these contaminants. As analytical 

methods improve and detection limits and corresponding 

analytical reporting levels decrease into the nanogram-per-liter 

range, however, it is important to consider that the detection of 

pharmaceutical and other chemicals in drinking water may not 

imply a risk to human health (Benotti and others, 2009). More 

research is warranted to determine the potential risk associated 

with chronic exposure to trace concentrations of pharmaceutical and other unregulated contaminants in drinking water 

(Novak and others, 2011).

Drinking-Water Withdrawals and Distribution in 

the Watershed

After Boston’s water supply, the Merrimack River is 

the second largest surface-water source of drinking water in 

New England. Treated river water supplies 135,000 people 

through the LRWU; an additional 165,000 residents in 

Lawrence, Methuen, Andover, and Tewksbury, Mass., also 

use Merrimack River water. In New Hampshire, there is only 

one community drinking-water intake along the main stem. 

The Nashua drinking-water system pumps a portion of its 

water from the Merrimack River to supply the city and a few 

surrounding towns. Numerous farms and several municipal 

drinking-water well fields also pump water from the river. 

Most community water systems in New Hampshire rely on 

groundwater for their supplies (New Hampshire Department 

of Environmental Services, 2009). Demand for water 

resources will likely increase as the population increases in 

the watershed, and resource managers attempt to develop new 

sources to meet potable-water needs. Most of the aquifers in 

unconsolidated sand and gravel have already been developed 

for public supply, leaving surface water and bedrock aquifers 

as the 

only other viable sources for large developments in the 

future (Sarah Flanagan, U.S. Geological Survey, written 

commun., 2010). 

Sample Collection and Analysis

While the focus of this study was on the occurrence of 

pharmaceuticals in source water from the Merrimack River, 

the basic study design and methods of sample collection and 

analysis followed those of the larger USGS SWQA.

Site Selection and Field-Data Collection

The Merrimack River was chosen as the site for the 

pharmaceutical investigation because it met specific criteria 

set out by the SWQA study design (Delzer and Hamilton, 

2007). The SWQA site-selection criterion called for a surfacewater source that is used to provide drinking water to a large 

population in the northeastern United States. The Merrimack 

River met this criterion in Massachusetts and New Hampshire. 

Additionally, the Merrimack River Basin extends over a large 

area and encompasses many land-use practices and potential 

sources of contamination; therefore, it was thought likely to 

carry some human, livestock and other agricultural, industrial, 

and wastewater contaminants to drinking-water intakes 

downstream. The SWQA program also investigates smaller 

drinking-water sources across the Nation—for example, 

the Hatfield, Mass., drinking-water source (Brown and 

Trombley, 2009). 

Source- and finished-water samples were collected 

periodically from April 2008 through June 2009. Raw 

Merrimack River source water was sampled through an 

access door in the concrete floor of the LRWU intake facility 

enclosing a wet well at the edge of the river and processed 

onsite in a mobile USGS laboratory. Samples of the finished 

water were collected from a continuously running spigot in the 

laboratory of the LRWU in the main building of the treatment 

plant. Finished-water samples were collected about 5 hours 

after raw-water samples to match the expected time of travel 

through the treatment process and to collect both samples 

from the same parcel of water. Source and finished drinkingwater samples were collected by using trace-level sampling 

protocols (Wilde and others, 2004). 

Sample Processing and Laboratory Analysis

Grab samples of raw source water were collected by lowering a tethered weighted-bottle sampler equipped with either 

a clean 1-liter (L) Teflon bottle or a new 1-L baked amberglass bottle. About 10 L of raw water was composited in a 

14-L Teflon churn splitter. The composite sample was mixed 

in the churn, and samples were split from the 10-L composite 

for each monthly sampling round. All water samples were 
6 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

analyzed for physical characteristics (temperature, specific 

conductance, pH, and dissolved oxygen), E. coli bacteria, 

pharmaceutical compounds and metabolites. Results of analyses for only pharmaceuticals, bacteria, and field characteristics 

are reported here. Samples for determination of other SWQA 

analytes were collected, processed, and shipped together for 

analysis at the USGS National Water Quality Laboratory 

(NWQL) in Lakewood, Colo.; these data are reported in a separate USGS NAWQA publication (Carter and others, 2010).

Measurements of physical characteristics were made with 

a multiparameter water-quality monitoring instrument calibrated before use on the same day as sampling in accordance 

with manufacturer’s instructions and USGS protocols (Wilde 

and others, 2004). For the raw-water measurements, the 

instrument was lowered to about 3 ft below the water surface 

inside the wet well; finished-water measurements were made 

by plumbing the flow from the laboratory tap through a cell 

attached to the instrument.

All raw-water samples were filtered through a 

0.7-micrometer (μm) glass-fiber filter on a free-standing 

aluminum filter plate placed inside an isolation chamber. 

A Teflon diaphragm pump with C-Flex tubing was used to 

force the raw-water sample through the filter membrane 

into 1-L baked amber-glass sample bottles. Water pressure 

at the laboratory tap was sufficient to force finished-water 

samples through the plate filter. Finished water was collected 

in sample bottles containing 0.1 gram (g) of ascorbic acid 

and 7.8 g of rinsed Trizma pH-7 buffer. Free chlorine was 

reduced with the ascorbic acid, and samples were buffered 

to pH 7 to minimize acid-catalyzed hydrolysis of analytes 

during shipping and handling (Valder and others, 2008). Once 

the samples were collected in prelabeled, sterile, amber-glass 

bottles, they were placed in resealable bags, wrapped in foam 

packing material, inserted into large bags in plastic coolers 

filled with ice, chilled to 4 degrees Celsius (°C), and shipped 

overnight to the NWQL for analysis. Samples were analyzed 

for pharmaceuticals by solid-phase extraction onto chemically 

modified styrene-divinylbenzene resin, followed by highperformance liquid chromatography/mass spectrometry 

(Furlong and others, 2008).

Raw-water E. coli bacteria samples were collected in 

sterile bottles attached to the weighted-bottle sampler that 

was lowered through the floor into the wet well. Bacteria in 

the samples were enumerated by using modified mTEC agar 

and membrane filtration (U.S. Environmental Protection 

Agency, 2000). The process of sample plating was completed 

onsite inside the USGS mobile laboratory. The plates 

were then incubated for 24 hours, after which colonies on 

the plates were photographed and counted at the USGS 

Massachusetts-Rhode Island Water Science Center laboratory 

in Northborough, Mass.

Quality of Finished Water

The QA plan for this study was designed with the 

primary objective of obtaining environmental data that are 

representative of the raw and finished water collected during 

the study period. Specific guidance for the collection of 

samples was obtained from the USGS National Field Manual 

for the Collection of Water-Quality Data (U.S. Geological 

Survey, variously dated).

Quality-Assurance and Quality-Control Samples

The QA plan established protocols that were followed 

to ensure consistency throughout the project. In addition to 

consistent protocols, quality-control (QC) samples were collected to assess the data. Quality-control samples helped verify 

analytical results and consisted of four blank samples, two 

replicate samples, and two spike samples. Blank samples were 

collected to check for potential contamination in the sampling 

process and laboratory analysis. Replicate samples were used 

to check laboratory variability, and spike samples helped 

assess analytical accuracy.

Four blank samples were collected during the study: two 

field blanks and two source-solution blanks. Field blanks were 

collected in the same manner and setting as the environmental samples, except that deionized water was used in place of 

the environmental sample. Source-solution blanks contained 

nitrogen-purged organic-free deionized water. Blanks were 

always collected in bottles containing the dechlorination 

agent ascorbic acid to assess whether the ascorbic acid caused 

analytical interferences. No pharmaceutical analytes were 

detected in any of the blank samples (table 2), indicating that 

samples were not contaminated during the sampling process 

and laboratory analysis.

Replicate samples are additional samples that are 

designed to be identical in composition to the corresponding 

environmental samples. Replicate samples provide a measure 

of bias and variability for the methods of sample collection, 

processing (churning and filtering), and laboratory analysis, 

and for possible effects such as analyte degradation prior to 

laboratory analysis (Smith, 2008). Replicate samples were collected twice—once from raw, untreated source water and once 

from finished, treated drinking water. There were no measurable differences in concentrations of any analytes in any of the 

replicate samples (table 2). Caffeine and carbamazepine were 

detected in both the raw-water sample and its QC replicate, 

but the concentrations were too small to be reliably quantified.

To produce laboratory-spike samples, additional environmental replicate samples were collected, processed, and 

shipped to the NWQL. These samples were subsequently 

fortified at 0.25 micrograms per liter (μg/L) for all pharmaceuticals tested (table 2), and then analyzed. The percent 

recovery for each target analyte added to the environmental 

sample is used to determine bias and variability arising from 
Quality of Finished Water 

7

Table 2. Concentrations of pharmaceutical analytes in quality-control samples and ranges of percent recoveries of known concentrations of compounds added to samples.[μg/L, micrograms per liter; <, less than; --, not measured]

Quality-assurance sample type Date

1,7-Dimethylxanthine

(μg/L)

Acetaminophen

(μg/L)

Albuterol

(μg/L)

Caffeine

(μg/L)

Carbamazepine

(μg/L)

Carbamazepine-d10

(percent recovered)

Codeine

(μg/L)

Cotinine

(μg/L)

Raw water Oct. 22, 2008 <0.120 <0.080 <0.060 <0.200* <0.040* 75.8 <0.040 <0.026Raw-water replicate Oct. 22, 2008 <.120 <.080 <.060 <.200* <.040* 77.1 <.040 <.026Finished water Oct. 22, 2008 <.120 <.080 <.060 <.200 <.040 86.0 <.040 <.026Finished-water replicate Oct. 22, 2008 <.120 <.080 <.060 <.200 <.040 67.3 <.040 <.026Blank water Apr. 16, 2008 <.100 <.080 <.040 <.060 <.040 101 <.040 <.026Blank water Nov. 19, 2008 <.120 <.080 <.060 <.200 <.040 137 <.040 <.026Blank water Nov. 19, 2008 <.120 <.080 <.060 <.200 <.040 135 <.040 <.026Blank water Jan. 8, 2009 <.120 <.080 <.060 <.200 <.040 95.0 <.040 <.026

Quality-assurance sample treatment Date 1,7-Dimethyl- xanthine Acetamino- phen Albuterol Caffeine Carbamazepine Carbamazepine-d10 Codeine Cotinine

Finished water sample May 21, 2008 <.100 <.080 <.040 <.060* <.040 35.0 <.040 <.026Percent spike recovered with ascorbic 

acid treatment

May 21, 2008 68.5 47.7 40.7 112 124 -- 82.2 95.2

Percent spike recovered without ascorbic 

acid treatment

May 21, 2008 69.4 49.3 12.4 129 101 -- 49.8 93.6

Quality-assurance sample type Date

Dehydronifedipine

(μg/L)

Diltiazem

(μg/L)

Diphenhydramine

(μg/L)

Ethyl nicotinate-d4

(percent 

recovered)

Sulfamethoxazole

(μg/L)

Thiabendazole

(μg/L)

Trimethoprim

(μg/L)

Warfarin

(μg/L)

Raw water Oct. 22, 2008 <0.080 <0.080 <0.040 74.0 <0.160 <0.060 <0.020 <0.100

Raw-water replicate Oct. 22, 2008 <.080 <.080 <.040 72.8 <.160 <.060 <.020 <.100Finished water Oct. 22, 2008 <.080 <.080 <.040 82.9 <.160 <.060 <.020 <.100Finished-water replicate Oct. 22, 2008 <.080 <.080 <.040 63.9 <.160 <.060 <.020 <.100Blank water Apr. 16, 2008 <.060 <.040 <.050 100 <.100 <.100 <.040 <.060Blank water Nov. 19, 2008 <.080 <.080 <.040 156 <.160 <.060 <.020 <.100Blank water Nov. 19, 2008 <.080 <.080 <.040 159 <.160 <.060 <.020 <.100Blank water Jan. 8, 2009 <.080 <.080 <.040 94.7 <.160 <.060 <.020 <.100

Quality-assurance sample treatment Date Dehydronife- dipine Diltiazem Diphenhy- dramine Ethyl nicotinate-d4 Sulfa- methoxazole Thiabenda- zole Trim- ethoprim Warfarin

Finished water sample May 21, 2008 <.060 <.040 <.050 32.5 <.100 <.100 <.040 <.060Percent spike recovered with ascorbic 

acid treatment

May 21, 2008 114 94.1 81.5 -- 132 59.3 84 97.4

Percent spike recovered without ascorbic 

acid treatment

May 21, 2008 100 2.4 26.5 -- 36.6 59 45.8 22.7

*Analyte detected at a concentration that could not be reliably quantified.
8 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

(1) the degradation of target analytes during shipment to and 

holding by the laboratory, (2) the analytical method, and (3) 

interferences that mask or enhance determinations of the target 

analytes in the environmental sample or produce matrix effects 

(Smith, 2008). 

In general, there was significant improvement in percent 

recovery of spiked compounds with the addition of ascorbic 

acid. Percent recoveries in the absence of ascorbic acid ranged 

from 2.4 for diltiazem to 129 for caffeine (table 2). With 

the addition of ascorbic acid, percent recovery of diltiazem 

increased to 94.1 and other low recoveries were also increased. 

Overall, percent recoveries in the presence of ascorbic acid, 

which was routinely applied to the finished-water samples, 

ranged from 40.7 for albuterol to 132 for sulfamethoxazole. 

In addition to the QC samples collected during this project, the NWQL routinely analyzes other types of QC samples 

including laboratory-reagent blanks, interference-check 

solutions, laboratory control samples, standard-reference 

materials, laboratory-reagent spike samples, and laboratory duplicate samples to test and track method performance 

(Garbarino and others, 2006; Furlong and others, 2008). The 

NWQL also adds surrogate compounds (carbamazepine-d10 

and ethyl nicotinate-d4) to all samples for routine determinations of percent recovery. Surrogate compounds are expected 

to react similarly to the targeted environmental analytes in the 

laboratory. Because these compounds are not normally found 

in the environment, the recovery of the surrogate compounds 

can be used to qualify the performance of the analysis (Smith, 

2008). The percent recovery of carbamazepine-d10 in QA 

samples ranged from 35.0 to 137 (table 2), whereas the percent 

recovery of ethyl nicotinate-d4 in QA samples ranged from 

32.5 to 159. The variations in recoveries observed in method 

surrogate compounds and in laboratory matrix-spike samples 

likely result from sample-specific matrix effects as well as 

losses during sample preparation and handling. The ranges of 

recoveries reported here are comparable to previously published observations for surface-water samples (Furlong and 

others, 2008).

Pharmaceuticals and Water-Quality 

Constituents in Merrimack River Source Water

Samples were collected periodically from April 2008 

through June 2009 and did not target any particular flow 

regime (fig. 2). Thus, Merrimack River water was collected 

and analyzed from flows that were above, below, and about 

average compared to long-term daily mean flow records. 

Physical characteristics were measured and bacteria samples 

collected during all 14 SWQA sampling rounds. Samples for 

pharmaceutical compounds were collected during 12 of the 

14 rounds (fig. 2, table 3).

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

Jan.

Feb.

Mar.

Apr.

May

Jun.

Jul.

Aug.

Sept.

Oct.

Nov.Dec.

Jan.

Feb.

Mar.

Apr.

May

Jun.

 Daily mean discharge

Water-quality samples

collected

Historical (1923−2009)

daily mean discharge

River flow,

in cubic feet per second

EXPLANATION

Jul.

2008 2009

Figure 2. Daily mean river flow at the U.S. Geological Survey streamgage on the Merrimack River below the confluence with the 

Concord River at Lowell, Massachusetts, for January 2008 through July 2009, compared with historical mean daily river flows for the 

period June 1923 through September 2009, and times when samples were collected for chemical analysis.
Quality of Finished Water 

9

Table 3. Analytical results for human-health pharmaceuticals measured in raw source water and finished drinking water at the Lowell Regional Water Utility, April 2008–May 2009.[μg/L, micrograms per liter; <, less than]

Sampling date

1,7-Dimethylxanthine

(μg/L)

Acetaminophen

(μg/L)

Albuterol

(μg/L)

Caffeine

(μg/L)

Carbamazepine

(μg/L)

Codeine

(μg/L)

Cotinine

(μg/L)

Dehydronifedipine

(μg/L)

Diltiazem

(μg/L)

Diphenhydramine

(μg/L)

Sulfamethoxazole

(μg/L)

Thiabendazole

(μg/L)

Trimethoprim

(μg/L)

Warfarin

(μg/L)

Raw water

Apr. 16, 2008 <.100 <.080 <.040 <.060* <.040 <.040 <.026 <.060 <.040 <.050* <.100 <.100 <.040 <.060May 21, 2008 <.100 <.080 <.040 <.060* <.040* <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060June 18, 2008 <.100 <.080 <.040 <.060* <.040* <.040 <.026 <.060 <.040 <.050* <.100 <.100 <.040 <.060July 16, 2008 <.100 <.080 <.040 <.060 <.040* <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060Sept. 11, 2008 <.100 0.084 <.040 0.068 <.040 <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060Oct. 22, 2008 <.120 <.080 <.060 <.200* <.040* <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Nov. 19, 2008 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Jan. 8, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Feb. 18, 2009 <.120 <.080* <.060 <.200* <.040 <.040 <.026* <.080 <.080 <.040 <.160 <.060 <.020 <.100Mar. 18, 2009 <.120 <.080* <.060 <.200* <.040 <.040 <.026* <.080 <.080 <.040 <.160 <.060 <.020 <.100Apr. 22, 2009 <.120 <.080* <.060 <.200* <.040* <.040 <.026* <.080 <.080 <.050* <.160 <.060 <.020 <.100May 20, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100

Finished water

Apr. 16, 2008 <.100 <.080 <.040 <.060* <.040 <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060May 21, 2008 <.100 <.080 <.040 <.060 <.040 <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060June 18, 2008 <.100 <.080 <.040 <.060* <.040* <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060July 16, 2008 <.100 <.080 <.040 <.060 <.040* <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060Sept. 11, 2008 <.100 <.080 <.040 <.060 <.040 <.040 <.026 <.060 <.040 <.050 <.100 <.100 <.040 <.060Oct. 22, 2008 <.120 <.080 <.060 <.200 <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Nov. 19, 2008 <.120 <.080 <.060 <.200 <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Jan. 8, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Feb. 18, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Mar. 18, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100Apr. 22, 2009 <.120 <.080 <.060 <.200* <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100May 20, 2009 <.120 <.080 <.060 <.200 <.040 <.040 <.026 <.080 <.080 <.040 <.160 <.060 <.020 <.100

*Analyte detected at a concentration that could not be reliably quantified.
10 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

Of the 14 prescription and nonprescription pharmaceutical compounds analyzed in raw Merrimack River source 

water, only 2 were detected at concentrations greater than their 

analytical reporting levels (RL). Concentrations of acetaminophen, a nonprescription analgesic (0.084 μg/L), and caffeine 

(0.068 μg/L) marginally exceeded the RLs in the September 

2008 samples (table 3). There were additional detections of 

acetaminophen; caffeine; carbamazepine, an antiepileptic; 

cotinine, a metabolite of nicotine; and diphenhydramine, a 

nonprescription antihistamine, during the 14-month study 

(table 3), but none at concentrations large enough to be reliably quantified. The estimated concentrations were above the 

analytical-method detection limit but below the RL. The RL is 

defined as two times the long-term analytical method detection 

limit observed by the laboratory (Furlong and others, 2008). 

Adjustments to RLs are commonly made by the NWQL (for 

example, in October 2008 the RL for albuterol was changed 

from 0.040 to 0.060 μg/L) and are based on statistical quantification of the analytical-method performance. The goal is to 

maintain the rate of false-positive results at no more and no 

less than 1 percent. An explanation of how analytical RLs are 

determined is given elsewhere (Childress and others, 1999).

Physical characteristics and E. coli bacteria were also 

measured in raw-water samples, and the results compared to 

applicable standards. The data were consistently within the 

standards of the Commonwealth of Massachusetts and met criteria established by the U.S. Environmental Protection Agency 

(USEPA) for the physical characteristics measured (table 4). 

The USEPA issues guidance in the form of National surfacewater-quality criteria for approximately 150 contaminants 

to protect aquatic life and human health. These criteria are 

published pursuant to Section 304(a) of the CWA and provide 

guidance for states and tribes to use in adopting water-quality 

standards (U.S. Environmental Protection Agency, 2009). 

The Massachusetts Department of Environmental Protection 

(MassDEP) issues surface-water-quality standards (Massachusetts Department of Environmental Protection, 2007) incorporating USEPA guidance for site-specific conditions. The intent 

of these standards is to support a designated-use classification, 

such as habitat for fish and aquatic life or a human use, such 

as primary-contact recreation (for example, swimming or fishing), secondary-contact recreation (for example, sport fishing 

or boating; fig. 3), or use as a drinking-water supply. 

Raw-water measurements of pH were consistent with the 

MassDEP criterion for this segment of the Merrimack River: 

within the range of 6.5 through 8.3 standard units (table 4). 

The pH of finished water is adjusted in the treatment process to be slightly basic—in the range of 7.4 to 8.4 standard 

units— to aid in the coagulation, flocculation, and removal of 

suspended sediment and other impurities. An added benefit 

Table 4. Physical characteristics and bacterial concentrations in samples of raw source water and finished drinking water collected 

monthly at the Lowell Regional Water Utility, April 16, 2008, through June 17, 2009.

[°C, degrees Celsius; μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; CFU/100 mL, colony forming units per 100 milliliters; --, not sampled]

Date 

Temperature

(°C)

Specific conductance 

(μS/cm)

pH

(standard units)

Dissolved oxygen 

(mg/L)

E. coli

(CFU/100 mL)

RawwaterFinished 

water

Raw 

water

Finished 

water

Raw 

water

Finished 

water

Raw 

water

Finished 

water

Raw 

water

Finished 

water

2008

Apr. 16, 2008 6.4 -- 76 155 7.1 8.0 10.4 -- 2 --

May 21, 2008 15.1 15.9 147 209 6.8 7.7 9.3 8.9 12 --

June 18, 2008 22.2 22.7 159 220 6.8 7.9 7.4 7.3 28 --

July 16, 2008 25.4 25.8 170 208 6.6 7.6 7.6 7.6 9 --

Aug. 13, 2008 19.1 20.2 75 156 6.7 7.8 7.0 8.3 190 --

Sept. 11, 2008 19.3 20.6 107 177 7.0 7.6 7.1 8.1 99 --

Oct. 22, 2008 15.1 14.1 143 206 6.9 7.7 10.8 11.0 18 --

Nov. 19, 2008 6.2 12.2 78 150 6.8 7.7 12.6 12.3 17 --

2009

Jan. 8, 2009 0.0 8.1 140 199 6.8 7.7 15.7 13.8 3 --

Feb. 4, 2009 0.4 4.4 160 220 6.7 8.0 15.4 15.1 -- --

Feb. 18, 2009 0.5 4.8 141 192 6.6 7.8 12.5 13.4 2 --

Mar. 18, 2009 2.8 6.1 130 191 6.7 8.0 12.6 12.8 1 --

Apr. 22, 2009 10.0 12.2 128 206 6.7 7.8 10.6 10.8 25 --

May 20, 2009 16.0 17.6 123 194 6.5 7.8 8.8 9.1 13 --

June 17, 2009 17.9 19.0 98 164 6.5 7.7 8.2 8.3 120 --
Quality of Finished Water 11

Figure 3. Kayakers paddling on the Merrimack River near Lowell, 

Massachusetts, June 2009.

of slightly basic drinking water in the distribution system is a 

reduction in the corrosion potential of residential plumbing, 

heating equipment, and water fixtures; heavy metals, such as 

lead in solder and copper in pipes, may dissolve under acidic 

conditions. In this study, the pH of finished-water samples was 

consistently within the range of 7.6 to 8.0 (table 4).

Dissolved-oxygen levels in the raw water always 

exceeded the MassDEP warm-water minimum of 5.0 milligrams per liter (mg/L) for this segment of the Merrimack 

River. The lowest dissolved-oxygen measurement (7.0 mg/L) 

was recorded in August 2008. It is interesting to note that 

this measurement also exceeds the cold-water minimum 

(6.0 mg/L) for this river. Temperature measurements were 

always lower than the maximum of 28.3°C for warm-water 

fisheries. The highest temperature of 25.4°C was recorded in 

July 2008, and the lowest was 0.0°C in January 2009 (table 4). 

E. coli concentrations were determined for raw water 

collected at the intake. The largest E. coli concentration, 

190 colony-forming units per 100 milliliters (CFU/100 mL), 

was measured in August 2008. The August 2008 result 

was below the Massachusetts criterion for a single sample 

collected at a site far from bathing beaches (235 CFU/100 mL 

maximum). Additionally, the criterion specifies that the 

geometric mean of all E. coli samples taken within the most 

recent 6 months shall not exceed 126 CFU/100 mL (based 

on a minimum of five samples). Following this calculation 

algorithm for the geometric mean, the E. coli concentrations 

measured in this study never exceeded 34 CFU/100 mL for 

six consecutive monthly samples. These relatively low E. coli

counts are consistent with other water-quality results from 

this study, including the few detections of pharmaceutical 

compounds at reportable concentrations.

Annual variations in Merrimack River flow conditions 

were well represented in the study: sampling was conducted 

during high and low flows and in all seasons. The monthly 

sampling schedule, however, may have missed certain hydrologic events that could have transported greater concentrations of OWCs to the sampling site. Based on the size of the 

watershed, it is likely that runoff volume effectively dilutes 

any contaminant signal. It is also likely, however, that recent 

efforts to separate stormwater- and wastewater-discharge 

systems and the development of outreach programs to educate 

the public about the effects of nonpoint-source pollution and 

proper practices for the disposal of pharmaceuticals in the 

reaches upstream from the LRWU have greatly reduced the 

potential for contamination at the LRWU intake.

Effects of Treatment on Pharmaceutical 

Compounds in Merrimack River Source Water

Municipal drinking-water treatment plants (DWTPs) 

are designed to remove contaminants and other objectionable 

materials from raw water through the treatment process. Most 

DWTPs use a combination of processes including coagulation, 

flocculation, sedimentation, primary disinfection, filtration, 

secondary disinfection, and fluoridation. The LRWU uses 

chlorination disinfection, flocculation, sand- and dual-media 

filtration, granular activated-carbon absorption, pH adjustment, and fluoridation. Chlorination and other oxidationtreatment technologies (such as ozonation) are effective at 

removing bacteria and other pathogens from drinking water. 

Additional benefits of chlorination (and ozonation) have been 

reported to include the effective removal (or transformation 

to oxidation byproducts) of some pharmaceuticals and other 

OWCs (Westerhoff and others, 2005). Westerhoff found that 

chlorine treatment oxidized more than 80 percent of the compounds tested in bench-scale experiments. These compounds 

were always oxidized more effectively by ozonation, but 

some compounds were poorly oxidized by either treatment. 

Westerhoff and others (2005) also reported improved removal 

of some OWCs by activated-carbon treatment.

Samples of finished water from the LRWU did not 

contain reportable levels of any of the pharmaceuticals 

measured in this study; however, two of the five compounds 

detected in corresponding raw-water samples (caffeine and 

carbamazapine) were detected in finished water at levels 

that could not be reliably quantified. Detection of these 

two compounds in the finished water samples may indicate 

that they are resistant to removal through the drinkingwater treatment process, but could also be indicative of 

a false-positive result. Carbamazepine, in particular, has 

been observed to persist through drinking-water treatment 

processes (Stackelberg and others, 2004; Benotti and others, 

2009). None of the other 12 pharmaceuticals was detected 

in any of the finished-water samples (tables 1 and 3). Recent 

advances in analytical methods have allowed quantification 

of pharmaceutical compounds at nanogram-per-liter 
12 Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, Massachusetts, 2008–09

concentrations. The work of Benotti and others (2009) is 

notable in that analytical results are reported at concentrations 

below reporting levels of the methods employed by the 

USGS NWQL and reported on here. Our results are at tenths 

to hundredths of a microgram per liter reporting levels. It is 

possible that additional pharmaceutical compounds would 

have been detected using methods with nanogram-per-liter 

reporting levels.

No drinking-water standards or health advisories have 

been established for any of the pharmaceutical compounds 

detected in this study, and monitoring of these contaminants in 

the Nation’s waters used for public supply is lacking. Furthermore, drinking-water criteria currently are based on the toxicity of individual compounds and not combinations of compounds. Little is known about potential human-health effects 

associated with chronic exposure to trace levels of multiple 

OWCs through routes such as drinking water (Stackelberg and 

others, 2004).

Summary

The U.S. Geological Survey, in cooperation with the 

Massachusetts Department of Environmental Protection, 

examined the presence of 14 commonly used pharmaceutical 

compounds and fecal-indicator bacteria in Merrimack River 

water, which is used as a drinking-water source for more than 

135,000 residents and businesses in the communities of Lowell, Dracut, Tyngsboro, and Chelmsford in eastern Massachusetts. Samples of the raw, untreated source river water were 

collected at the surface-water intake of the Lowell Regional 

Water Utility (LRWU), and the same parcel of water was sampled after treatment and before entering the distribution system 

(finished-water samples). Water samples were collected periodically from April 2008 through June 2009 and included 12 

source-water samples paired with 12 finished-water samples, 

plus several quality-control samples. Additional source-water 

samples were collected for determination of concentrations of 

the fecal-indicator E. coli and measurements of several physical characteristics.

Despite many potential sources of contamination in 

the drinking-water source area, only 2 of the 14 target analytes were found at concentrations above the reporting level. 

Acetaminophen, a nonprescription analgesic, and caffeine 

were measured in the September 2008 source-water samples 

at concentrations of 0.084 and 0.068 micrograms per liter, 

respectively. Three other compounds—carbamazepine, an 

antiepileptic; cotinine, a metabolite of nicotine; and diphenhydramine, a nonprescription antihistamine—also were 

detected in source-water samples, but their concentrations 

were too low to be reliably quantified. Values measured for 

physical characteristics, including temperature, pH, specific 

conductance, dissolved oxygen, and E. coli bacteria, were 

always within regulatory guidelines.

None of the 14 pharmaceuticals was found in the finished 

water at a reportable concentration, defined as two times the 

long-term detection limit observed by the U.S. Geological 

Survey National Water Quality Laboratory. Two compounds, 

however, caffeine and carbamazepine, were detected in 

finished water, but at concentrations that were too low to be 

reliably quantified and could be considered as false positives. Physical and chemical characteristics of the finished 

water were comparable to those of the raw water and reflected 

adjustments made during the 5-hour treatment process. E. coli

was not analyzed in finished water because disinfection during 

the treatment processes is effective at removing bacteria and 

other pathogens from the drinking-water supply; the LRWU 

also routinely conducts these analyses as part of their consumer-confidence protocols. 

It is possible that the monthly sampling schedule failed 

to detect contamination resulting from storm events, although 

sampling did include both high and low flow conditions. It is 

also possible that contaminant signals were effectively diluted 

by the large discharge volumes at that point in the river. It 

is also likely, however, that reductions in pollution potential 

may have been realized through efforts to eliminate combined 

sewer overflows from several communities in the watershed, 

and that future plans to remediate existing combined sewer 

systems will continue to improve water quality at downstream 

reaches where the Merrimack River is used as the drinkingwater source.

References Cited

Aitken, R.J., Kopman, P., and Lewis, S.E.M., 2004, Seeds of 

concern: Nature, v. 432, p. 48–52.

Barnes, K.K., Christenson, S.C., Kolpin, D.W., Focazio, 

M.J., Furlong, E.T., Zaugg, S.D., Meyer, M.T., and Barber, 

L.B., 2004, Pharmaceuticals and other organic waste water 

contaminants within a leachate plume downgradient of a 

municipal landfill: Ground Water Monitoring and Remediation, v. 24, no. 2, p. 119–126.

Barnes, K.K., Kolpin, D.W., Furlong, E.T., Zaugg, S.D., Meyer, 

M.T., and Barber, L.B., 2008, A national reconnaissance of 

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p. 597–603.
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in Running Gutter Brook water used for public supply near 

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Fact Sheet 2009–3076, 6 p.

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Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

Massachusetts-Rhode Island Water Science Center

10 Bearfoot Road

Northborough, MA 01532

dc_ma@usgs.gov

or visit our Web site at:

http://ma.water.usgs.gov
Massey and Waldron—Pharmaceutical Compounds in Merrimack River Water Used for Public Supply, Lowell, MA, 2008–09—Scientific Investigations Report 2011-5192