Determining the Cause of Elevated Lead Levels in DC

Getting the Lead
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o
out of DC Tap Water
Determining the Cause of

Elevated Lead Levels in DC

Treatment is underway to reduce lead levels in the
District's drinking water. Why did lead levels increase
in the first place? How did experts identify the most
appropriate treatment?

This Research Newsletter presents the results of
research funded by the DC Water and Sewer
Authority (DCWASA), the Washington
Aqueduct, and the U.S. Environmental
Protection Agency (EPA). The science of
drinking water in general, and the elevated lead
levels in particular, are complex. The purpose of
this Newsletter is to provide a general overview of
various research studies for the interested reader.
See the "More Information" section at the end of
this Newsletter for detailed reports of many of the
studies described here.
In this Newsletter...
The Culprit: Lead Service Lines .... 2
Lead Scale Analysis Provides
Key Information 4
Raising the pH is Not a Lead
Control Option 5
Orthophosphate Reduces
Lead Leaching in the Lab 5

Continuing Research 7
;,,
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Getting the Lead

out of DC Tap Water

The Culprit: Lead Service Lines
In order to control lead in drinking water,
DCWASA needed to identify the source of the
lead. Because laboratory tests showed that water
leaving the treatment plants and in the mains
contained almost no lead, DCWASA zeroed in on
service lines and home plumbing.

DCWASA worked with corrosion experts to develop
a lead profiling procedure at customers' homes to
track the release of lead. Lead profiling requires that
residents let the water sit in their plumbing system
for at least six hours. (This usually occurs while
Lead can leach from

*• lead solder used to weld pipes together;

>• faucets and fixtures;

>• bronze water meters; and

*• service lines that connect your house to
the water main under the street.

people are at work.) At the end of this holding
time, DCWASA personnel collect 15 to 20 1-liter
samples of water from the kitchen tap and analyze
each for lead.
Where Does DC's Drinking Water Come From?
WASHINGTON AQUEDUCT
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TREATMENT PLANT
LITTLE FALLS RAW WATER
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FAIRFAX COUNTY
ARLINGTON COUNTY
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AIRPORT
DC drinking water comes from the Potomac River and is treated by the Washington Aqueduct. The Aqueduct sells water
to DCWASA, as well as Arlington and Fairfax Counties in Virginia (The Aqueducts service area is shown in yellow).
DCWASA distributes the water to DC residents. EPA regulates the quality of the drinking water.
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letting the Lead
Based on the length and diameter of the household
plumbing, DCWASA can approximate where each liter
of water was stagnating during the holding time. For
example, the first liter of water drawn would have been
sitting in the faucet and home plumbing system. A few
samples later would represent water from the service
line between the house and the water main. The last
few samples would be from the water main under the
street. Most of these profiles were done at homes with
lead service lines.

Figure 1 shows typical lead profiling results for a home
with a lead service line. Water from the inside plumb-
ing and the water main had low lead levels. Lead levels
were highest in the water from the lead service lines.
Lead concentrations in water from the service lines
typically ranged from 70 parts per billion (ppb) to 150
ppb (EPA's lead action level is 15 ppb). Profiles from
out of DC Tap Water

homes without lead service lines always had low
lead concentrations.

Another important finding of DCWASA's lead
profiling work was that most of the lead is
dissolved, as opposed to particulate, lead.
DCWASA filters each water sample to separate
the dissolved and particulate lead so that they
can be measured separately. While the form of
the lead is not important in terms of health
effects, it can provide clues as to how lead gets
into drinking water. Particulate lead indicates
that the corrosion scale is detaching from the
pipe wall by a physical process. Dissolved lead,
which is the predominant form found in the
District's water, indicates that the lead is being
dissolved through a chemical or biochemical
reaction.
Figure 1 Lead Profiling Results from a House with a Lead Service Line
(Samples collected in early 2004)
120
110
100
go
80
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50

0
IN-HOUSE PLUMBING
LEAD SERVICE LINE
WATER MAIN
IIIIIHIIHIII
10
12
4568
Sample Number (Each Sample = 1 Liter of Water)
• Total Lead = Dissolved + Particulate • Dissolved Lead
14
16
19
Source: DCWASA

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Getting the Lead

out of DC Tap Water
Lead Scale Analysis Provides Key Information

DCWASA's lead profiling work indicates that most
of the lead in DC's drinking water is leaching from
lead service lines. What is causing this to happen?
And why now?

To answer these questions, scientists from EPA's
Office of Research and Development used a
procedure called X-ray diffraction. EPA obtained
sections of lead service lines that had been extracted
from the DC water system. The insides of the lines
were carefully scraped to remove the "scale" of lead
deposits that had formed over time. The removed
scale material was ground into a powder and spread
onto a quartz plate. A sophisticated machine
bombarded each plate with X-rays, then measured
how the rays diffracted (or changed direction) when
they hit the sample. Diffraction patterns are unique
for different chemicals. The diffraction patterns for
the DC samples told researchers the exact chemical
makeup of the lead scale. EPA repeated this test
with several lead service lines and verified the
findings using other methods.

The X-ray diffraction analysis showed that the lead
scale in DCWASA's system was made up mostly of
lead oxide (PbO2) compounds (Pb is the chemical
symbol for lead, O is the symbol for oxygen).
Although lead oxide scales have been identified in a
few other water systems, the majority of the lead
scales EPA has analyzed are made up primarily of
lead carbonate and lead hydroxy carbonate com-
pounds.
The Working Theory
Before 2000, chlorine was oxidizing
the lead and keeping it on the
pipes. When chlorine was
replaced with chloramines in late
2000, the lead was no longer being
oxidized and began dissolving very
slowly into the water.
Why is DC different? The working theory put
forward by EPA researchers is that the lead oxide
scale formed in the past when the water was treated
with chlorine. Prior to 2000, DCWASA maintained
a high level of chlorine in the drinking water distri-
bution system to control coliform bacteria. During
this time, chlorine oxidized the lead to form a PbO2
scale. PbO2 is generally "insoluble," meaning that it
does not dissolve into the water. When DCWASA
switched from a strong oxidant (chlorine) to a weaker
oxidant (chloramines) in late 2000, the lead was no
longer being oxidized and began slowly dissolving
into the water.

Field and laboratory studies confirm EPA's finding.
Most of the lead in DC's drinking water is dissolved
(not particulate) lead, indicating that a chemical
reaction similar to the one described here is taking
place. In the spring of 2004,
the disinfectant was changed
back from chloramines to
chlorine for one month to clean
out the pipes. Near the end of
this period, DCWASA noticed a
dramatic reduction in lead
levels.
Inside of lead service line extracted from DC water system
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letting the Lead
So why have the Aqueduct and DCWASA not
switched back to free chlorine permanently to
reduce lead leaching? The treatment was originally
changed from chlorine to chloramines to reduce the
levels of disinfection by-products (DBFs) in drink-
ing water. Some of these DBFs have been shown to
cause cancer and reproductive effects in laboratory
animals. Changing back to chlorine could increase
risks for all customers and would likely cause
DCWASA to exceed federal standards for DBFs.
out of DC Tap Water

This interplay of disinfection methods
and lead levels illustrates the challenges
that water systems face in attaining
simultaneous compliance with various
drinking water regulations.
Raising the pH is Not a Lead Control Option
Raising the pH is a common way to control lead
levels in drinking water. pH is an indication of the
acidity of water, with a pH of 7 considered neutral.
High pH levels (more basic water) can result in the
formation of less soluble lead compounds, meaning
that they will not dissolve into the drinking water.

Historically, the Washington Aqueduct has added
small amounts of lime (calcium oxide) to the water
to maintain a high pH and control for lead.
Minimum pH goals of 7.4 to 7.8 were set by EPA
in 2002, although typical pH values of DC water
were often higher. When the lead levels increased
in 2003, some technical experts recommended
adding more lime to raise the pH even more
(consistently above 8.8) to help curb the lead
leaching.

To study different lead control strategies, the
Washington Aqueduct and its expert consultants
used a computer model to predict how effective
each strategy would be. This "desktop" study was
also used to predict unintended consequences—
things that the water system does not want to
happen as a result of a new treatment.

When lime (calcium oxide) is added to water to raise
the pH, there is a concern that too much calcium
carbonate will precipitate out in solid form into the
drinking water. Calcium carbonate is the whitish-
gray substance that can clog shower heads or leave a
film on shower doors. It can clog pipes, foul water
heaters, and cause the water to have a white, cloudy
appearance.

The Aqueduct's computer model showed that adding
lime would cause too much calcium carbonate to
precipitate out into DC's drinking water. Thus, the
Aqueduct and its treatment experts concluded that
raising the pH of the water was not a viable solution
to the lead problem. They recommended that,
instead, orthophosphate treatment be used to reduce
lead in drinking water. Orthophosphate is a
tasteless, odorless, food-grade chemical that works by
reacting with lead to form a thin coating on the
inside of lead pipe and plumbing fixtures.
Orthophosphate Reduces Lead Leaching in the Lab
To complement the Washington Aqueduct's desk
top lead control study, DCWASA conducted a
series of loop experiments in the laboratory to test
the effectiveness of various lead corrosion control
strategies. These loop experiments involve circulat-
ing tap water through extracted lead service lines,
then measuring how much lead from the service
line leaches into the water.

One strategy tested in several loops was orthophos-
phate treatment. Figure 2 presents results from
"Stagnation Loop 3," which are typical of the

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Getting the Lead

out of DC Tap Water

orthophosphate treatment experiments. Each data
point on the graph represents the accumulated lead
concentration in water that has circulated through
lead service lines for approximately 16 hours. The
text at the top of the graph describes the experi-
mental testing conditions.

The time period labeled "No Treatment" shows
accumulated lead concentrations in untreated DC
tap water. During the no-treatment phase, contact
between the water and the lead service line resulted
in relatively high lead concentrations in tap water
(100 to 250 parts per billion). On May 12, 2004,
DCWASA began adding orthophosphate to the
water in the loop 3 experiments. Thereafter, lead
concentrations gradually decreased. Following
approximately 34 weeks of treatment, lead concen-
trations are less than 15 parts per billion.
To date, DCWASA has tested orthophosphate
treatment in a total of four recirculation loops.
Similar trends were seen for all loops: lead leaching
from lead service lines decreased when orthophos-
phate was added to the tap water. This information
was key in the decision to start adding orthophos-
phate system-wide in August 2004.
Treatment update: Results in 2005
show that the orthophosphate
treatment is working to reduce lead
leaching. WASA reported that of the
100 homes tested by WASA from
January - May 2005, 90 had lead levels
at or below 15 ppb.
Figure 2 Laboratory Data: Updated January 2005
Laboratory Pipe Loop Study
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Laboratory data from the stagnation loops should be interpreted with care. The amount of lead that leaches from a lead service
line depends on many factors. The first is the nature of the service line itself. DCWASA uses excavated lead service lines from
their system in all of their recirculation loops. The age of the service line, the way it was manufactured, and the quality of water it
received can influence the amount of lead that leaches into drinking water. Another factor is that laboratory experiments are
conducted under controlled conditions. In the distribution system and in individual homes, the quality of water can vary more
than it does in the laboratory environment.
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letting the Lead
Continuing Research
DCWASA, the Washington Aqueduct, and EPA
have agreed on a long-term research strategy to
ensure that the best overall quality of water is
provided to District residents. Below are
examples of some of the research studies
underway:
>• DCWASA is continuing the pipe loop
studies that have been underway. DCWASA
is also testing innovative alternatives to
service line replacement in the lab.
*• The Washington Aqueduct is evaluating the
effectiveness of orthophosphate and zinc
orthophosphate treatment using an intricate
flow-through pipe loop system. They are
comparing the two chemicals to determine
which chemical works best and to refine the
treatment process. In related research, the
Arlington Department of Environmental
Services and EPA are jointly funding re-
search to determine if adding zinc ortho-
phosphate would cause waste water treat-
ment problems.
>• EPA is continuing to analyze lead service
lines to assess how the lead scales inside the
pipes are changing as a result of orthophos-
phate treatment.
*• EPA is funding research to evaluate whether
grounding currents and galvanic coupling of
lead and copper service lines affect lead
corrosion.
>• The Aqueduct is conducting a pH manage-
ment study of whether the current practice
of using lime is the best way to maintain a
consistent pH or whether other options
could work more reliably.
*• DCWASA is conducting extensive water
quality monitoring to help manage the
system and prioritize their unidirectional
flushing program.
out of DC Tap Water

Continuing Consumer Advisory
Although recent lead monitoring in the District shows
that the orthophosphate treatment is working to
reduce lead leaching, it is important that District
residents continue to follow the consumer advisory for
flushing their taps and filtering before drinking the

water.

Residents in homes known to have or suspected of
having lead service lines should continue to:

ALVK\YS run the water in your home for 10 minutes
to flush the pipes before
drinking or using it for cooking.
counts as flushing, but you should
still run each faucet for 60
seconds before use.
Pregnant women, nursing mothers, and
children under 6 years old should only drink
filtered tap water. Flush the pipes for 10
minutes as noted above before using your home
filter.

To conserve water and save time after flushing your
taps each morning, fill up several clean containers of
filtered water that you can store in the refrigerator
and use during the day.

All residents should continue to:
*• Flush water from the tap for 60
seconds before drinking or
using it for cooking.
*• Use only COLD water for
drinking or cooking.
*• Remove and clean the strainer/
aerator/screen device on your faucet regularly.

>• Remember that boiling water will not remove lead!
For more information, see EPA's Website at http://www.epa.gov/dclead
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Getting the Lead

out of DC Tap Water

For more information:

U.S. EPA Safe Drinking Water Hotline 800/426-4791 http://www.epa.gov/dclead/

D.C. Water and Sewer Authority 202/787-2732 http://www.dcwasa.com/

D.C. Department of Health 202/671-0733 http://dchealth.dc.gov/

Washington Aqueduct 202/764-2753 http://washingtonaqueduct.nab.usace.army.mil/

A copy of the Aqueduct's desk top study of various corrosion control strategies is available on EPA's
website at http://www.epa.gov/dclead/CorrosionControl.pdf.

See EPA's website at http://www.epa.gov/dclead/chlorine.htm for more information on the 2004 switch
from chloramines to chlorine.

The research presented in this newsletter
was made possible by the DC Water and
Sewer Authority, the Washington
Aqueduct, the DC Department of Health,
the U.S. Environmental Protection
Agency, the Arlington County Department
of Public Works, and the Falls Church
Department of Environmental Services.
Valuable expertise was provided by
Virginia Polytechnic Institute, The
University of Washington, The University
of Illinois, HDR Engineering, Baker-Killam
Joint Venture, The U.S. Centers for
Disease Control and Prevention, Virginia
Military Institute, CH2M-HHI, George
Washington University School of Public
Health, and The Cadmus Group, Inc.
U.S. Environmental Protection Agency • D.C. Water and Sewer Authority • D.C. Department of Health • Washington Aqueduct
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