United Statrt Sewnw Advwwy EPA-SAB-OWC-92-010
Environmental Board lA-101] January 1932
PfOtaetion Agwiey
SEPA AN SAB REPORT: REVIEW
OF CORROSION RESEARCH
PROGRAM
REVIEW OF THE DRINKING WATER
RESEARCH DIVISION'S CORROSION
RESEARCH PROGRAM BY THE
DRINKING WATER COMMITTEE
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WOTTED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON B.C. 204«»
January 3, 1992
QFRCEOF
1BE ADMINISTRATOR
'' SCONCE ADVISORY BOABD
EPA-SAB-DWC-92-010
Honorable William K. leilly
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C 20460
Subject: Science Advisory Board review of the DrinMng Water Research Division's
Corrosion Research Program.
Dear Mr. Reilly;
The Science Advisory Board's DrinMng Water Committee (DWC) met in Cincinnatij
Ohio on May 9 and 10, 1991 to review the Environmental Protection Agency's DrinMng
Water Research Division's (DWRD) Corrosion Research Program, The Committee was asked
to review and evaluate the state-of-the-art use of pipe loop tests for the evaluation and
optimization of corrosion control treatment methods; and identify and consider the relative
severity and scope of the secondary impacts of regulated corrosion control. We further
subdivided these issues into the following five topics and offer the following response (more
detail on each issue is contained in the attached report):
1. The use of pipe loop tests for the evaluation and optimization of corrosion
control treatment methods.
We recommend that the DWRD continue its research with pipe loop tests to obtain data
that can be used to provide a better understanding of corrosion and control procedures.
2. The usefulness of methods other than pipe loop tests such as coupon tests and
electrochemical methods.
We recommend that studies be undertaken to determine whether the concentrations of
lead, copper, and other metals that enter water as a result of corrosion are directly related to
the measures of corrosion rate that are made using gravimetric and electrochemical methods.
These studies should be conducted in conjunction with pipe loop tests and studies of full-scale
systems.
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3. Standard protocol for evaluating corrosivity,
We recommend that the search for a standard protocol for evaluating corrosivity should
be undertaken starting with the simplest test, gravimetric—either with iron or lead test systems,
moving on to more complex approaches if this is unsuccessful.
4. Identification and consideration of the relative severity of the secondary impacts
of corrosion control procedure.
We recommend that studies be undertaken to determine how lime can be added to meet
the goals of the lead/copper rule, and at the same time, eliminate the operational problems
associated with adding it. Several secondary impacts of treatment to control corrosion were
identified that must be considered each time treatment is considered,
5, Changes in the direction of current research programs.
We recommend that research on the corrosion of brasses and the variety of available
solders be undertaken to determine effective control procedures. We further recommend the
research involving investigation of the chemical composition of scales be expanded to
determine the changes in the nature of the scale that occur during stagnation periods, the
relationship of these changes to both water composition, and the concentration of metals that
dissolve in the water. An additional topic requiring research is the role of microorganisms in
distribution systems on corrosion of iron, lead and copper. Further, we recommend that a
program be established whereby the EPA can use and benefit from corrosion research in other
countries.
We were pleased with the research program that was presented, and urge that EPA
accomplish the additional work that we have suggested. We would appreciate your response to
the major points we have raised.
Sincerely,
Dr/Raymond Loehr, Chair
Science Advisory Board
iair
Drinking Water Comi&fttee
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NOTICE
This report has been written as a part of the activities of the Science Advisory Board, a
public advisory group providing extramural scientific information and advice to the
Administrator and other officials of the Environmental Protection Agency, The Board is
structured to provide balanced, expert assessment of scientific matters related to problems
facing the Agency. This report has not been reviewed for approval by the Agency and, hence,
the contents of this report do not necessarily represent the views and policies of the
Environmental Protection Agency, nor of other agencies in the Executive Branch of the
Federal government, nor does mention of trade names or commercial products constitute a
recommendation for use.
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ABSTRACT
The Science Advisory Board's Drinking Water Committee (DWC) met in Cincinnati.,
Ohio on May 9 and 10, 1991 to review the Environmental Protection Agency's DrinMng
Water Research Division's (DWRD) Conosion Research Program. The Committee was asked
to review and evaluate the state-of-the-art use of pipe loop tests for the evaluation and
optimization of corrosion control treatment methods; and identify and consider the relative
severity and scope of the secondary impacts of regulated corrosion control. The Committee's
primary recommendations were: 1) that the DrinMng Water Research Division continue its
research with pipe loop tests to obtain data that can be used to provide a better understanding
of corrosion and control procedures; 2) that studies be undertaken to determine whether the
concentrations of lead, copper, and other metals that enter water as a result of corrosion are
directly related to the measures of corrosion rate that are made using gravimetric and
electrochemical methods; 3) that me search for a standard protocol for evaluating corrosivity
should be undertaJken starting with the simplest test, gravimetric-either with iron or lead test
systems, moving on to more complex approaches if this is unsuccessful; 4) that studies be
undertaken to determine how lime can be added to meet the goals of the lead/copper role, and
at the same time, eliminate the operational problems associated with adding it; and 5) that
research on the corrosion of brasses and the variety of available solders be undertaken to
determine effective control procedures. In summary, the Committee was pleased with the
research program that was presented t and urged that EPA accomplish the additional work
recommended.
Key Words: Corrosion research; corrosivity; drinking water; pipe-loop tests
11
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ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOAM)
DRINKING WATER COMMITTEE
Dr. Verne Ray, Medical Research Laboratory, Pfizer Inc., Groton, CT
Dr, William Glaze, University of North Carolina, Chapel Hill, NC, was Chairman during the
review, but subsequently resigned his position due to the press of other professional
duties. Dr. Ray was appointed Chairman on October 1, 1991.
MEMBERS/CONSULTANTS
Dr. Richard Bull, College of Pharmacy, Washington State University, Pullman, WA*
Dr. Gary Carlson, Department of Pharmacology and Toxicology, School of Pharmacy,
Purdue University, West Lafayette, IN*
Dr. Keith E. Cams, East Bay Municipal Utility District, Oakland, CA
Dr. Lenore S. Cleseeri, Rensseiaer Polytechnic, Troy, NY
Dr. William J. Haun, Maple Grove, MN
Dr, David Kaufman, Department of Pathology, University of North Carolina, Chapel Hill,
NC*
Dr. Nancy Kim, New York State Department of Health, Albany, NY
Dr. Ramon G, Lee, American Water Works Service Company, Inc, Voorhees, NJ
Dr. Edo D. Pellizzari, Research Triangle Institute, Research Triangle Park, NC
Dr, Vern SnceyinJk, Department of Civil Engineering, University of Illinois, Urbana, IL
Dr. Mark D. Sobsey, Department of Environmental Sciences and Engineering, School of
Public Health, University of North Carolina, Chapel Hill, NC*
Dr. James Symons, Department of Civil and Environmental Engineering, University of
Houston, Houston, TX
* Member who did not attend the meeting.
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SCIENCE ADVISORY BOARD STAFF
Mr, A. Robert Flaak, Assistant Staff Director and Acting Designated Federal Official, Science
Advisory Board (A-101F), U.S. EPA, 401 M Street, SW, Washington, DC 20460
Dr. C. Richard Cothera, Designated Federal Official (during the review), Science Advisory
Board (A-101F), U.S. EPA, 401 M Street, SW, Washington, DC 20460
Mrs. Frances Dolby, Staff Secretary, Science Advisory Board (A-101F), U.S. EPA, 401 M
Street, SW, Washington, DC 20460
IV
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TABLE OF CONTENTS
I. EXECUTIVE SUMMARY . , , . .' 1
2. INTRODUCTION , 3
2.1 Background , 3
2.2 Charge to the Committee , 3
3. DISCUSSION , , 4
3.1 Use of Pipe Loop Tests for the Evaluation and Optimization of
Corrosion Control Treatment Methods 4
3.2 The Usefulness of Methods Other than Pipe Loop Tests 5
3.3 Standard Protocol for Evaluating Corrosivity 6
3.4 Identification and Consideration of the Relative Severity of the
Secondary Impacts of Corrosion Control Procedures 6
3.5 Recommended Changes in Current Research Program Direction 7
4. CONCLUSIONS AND RECOMMENDATIONS 10
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1. EXECUTIVE SUMMARY
The Science Advisory Board's Drinking Water Committee (DWC) met in Cincinnati,
Ohio on May 9 and 10, 1991 to review the Environmental Protection Agency's Drinking
Water Research Division's (DWRD) Corrosion Research Program. The Committee was asked
to review and evaluate the state-of-the-art use of pipe loop tests for the evaluation and
optimization of corrosion control treatment methods; and identity and consider the relative
severity and scope of the secondary impacts of regulated corrosion control. In responding to
these charges, we further subdivided our deliberations into the following five topics:
1. The use of pipe loop tests for the evaluation and optimization of corrosion
control treatment methods.
The Committee recommends that the Drinking Water Research Division continue its
research with pipe loop tests to obtain data that can be used to provide a better understanding
of corrosion and control procedures. The research should be extended to systems of increasing
complexity, to better simulate the full-scale distribution system, and to investigate the effects
of corrosion on increases in concentrations of metals such as cadmium, antimony, and silver,
in addition to lead and copper.
2, The usefulness of methods other than pipe loop tests such as coupon tests
and electrochemical methods.
The Committee recommends that studies be undertaken to determine whether the
concentrations of lead, copper, and other metals that enter water as a result of corrosion are
directly related to the measures of corrosion rate that are made using gravimetric and
electrochemical methods* These studies should be conducted in conjunction with pipe loop
tests and studies of full-scale systems.
3. Standard protocol for evaluating corrosivity*
We recommend that the search for a standard protocol for evaluating conrosivity should
be undertaken starting with the simplest test, gravimetrie-either with iron or lead test systems,
moving on to more complex approaches if this is unsuccessful. We further recommend that
the candidate protocol should be evaluated in "corrosive" and "non-corrosive" waters in the
field, correlating the surrogate data to actual copper and lead concentrations.
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4, Identification and consideration of the relative severity of the secondary
impacts of corrosion control procedure,
We recommend that studies be undertaken to determine how lime can be added to meet
the goals of the lead/copper rule, and at the same time, eliminate the operational problems
associated with adding it.
5. Changes in the direction of current research programs.
The Committee recommends that research on the corrosion of brasses and the variety
of available solders be undertaken to determine effective control procedures. We further
recommend the research involving investigation of the chemical composition of scales be
continued, and expanded to determine the changes in the nature of the scale that occur during
stagnation periods, the relationship of these changes to both water composition, and the
concentration of metals that dissolve in the water. In addition, we recommend that a study of
the influence of microbes on corrosion in distribution systems be undertaken, including their
effect on corrosion of iron, lead, and copper. Furthermore, we recommend that research be
undertaken to determine the effects of organic compounds that can be present in drinking water
on corrosion. Finally, we recommend that a program be established whereby EPA researchers
can learn of the effectiveness of corrosion control procedures that have been used in other
countries and their applicability to situations in the United States.
In summary, the Committee was pleased with the research program that was presented,
and urge that EPA accomplish the additional work that we have recommended.
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2. INTRODUCTION
2.1 Background
A Panel of the Science Advisory Board's Drinking Water Committee met in Cincinnati,
Ohio on May 9 and 10, 1991 to review the Environmental Protection Agency Drinking Water
Research Division's Corrosion Research Program. Oral presentations by Dr, Robert Clark,
Ms. Barbara Wysock, Mr, Tom Sorg, Mr. Michael Sehock, and Mr. Marvin Gardels were
heard. No formal documents were presented for review.
The Committee was asked to review the utility of current procedures for evaluating
corrosion control treatment methods and to examine the impacts that treatments to control lead
and copper corrosion may have on preferred conditions for disinfection effectiveness, limiting
disinfectant by-product formation, iron and manganese sequestration, biofilm control, and
other regulated water quality parameters. Corrosion is of special concern because of the
health effects of corrosion products, such as copper and lead, that enter the drinking water,
and the integrity of the distribution system. The Committee was also asked to comment on the
direction of the current research program that is addressing corrosion issues.
Corrosion testing usually involves the use of pipe loops or coupons. Pipe loops are
small pipe networks that are built and operated in the laboratory to simulate some part of the
water distribution systems. Coupons are small pieces of metal that have been carefully
prepared for use in small volumes of water in the laboratory or for insertion into the
distribution system at strategic points. Coupon weight loss as a function of time is often
measured to determine corrosion rate.
2.2 Charge to the Committee
The Committee subdivided its responses into the following topics;
a) The use of pipe loop tests for the evaluation and optimization of corrosion
control treatment methods.
b) The usefulness of methods other than pipe loop tests.
c) Standard protocol for evaluating corrosivity.
d) Identification and consideration of the relative severity of the secondary impacts
of corrosion control procedure.
e) Changes in the direction of current research programs.
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3. DISCUSSION
The following sections (3.1, 3.2, 3.4, 3.5) include discussions of the issues brought to
the Committee by the Agency and one additional section (3.3) concerning the development of a
standard corrosion test protocol.
3.1 Use of Pipe Loop Tests for the Evaluation and Optimization of Corrosion Control
Treatment Methods
The pipe loop test is an excellent research tool that has provided much useful
information on the factors affecting corrosion and the means to control it, The Committee
believes that the pipe loop research now underway in the Drinking Water Research Division is
of very high quality and should provide useful results for the water treatment industry.
Several problems limit the usefulness of the pipe loop tests to utilities that must
optimize their corrosion control program. These problems can be adequately dealt with in a
research program, but create difficulties in interpreting the resulting data when used by utilities
for corrosion control treatment optimization. Some of the practical difficulties with the loop
tests are;
a. Variation introduced as a result of plumbing workmanship and materials during
construction of the pipe loop. Parallel pipe loop studies show wide variation in
results.
b. Pipe loop tests results from new materials can be significantly different than for
aged materials in the distribution system. The results most pertinent to utilities
are those with aged plumbing materials.
c. Depending upon the type of material and the water up to 12 months may be
required for a pipe-loop system to fully respond to changes in water treatment.
Therefore, to optimize treatment for corrosion control, each change in treatment
will require an extended period of testing before the effect of the treatment
change can be observed. This will unduly extend the test period of studies
involving multiple treatment options.
d. Each pipe loop test focuses rather narrowly on one or two materials such as
copper and lead, and will not reflect impacts on other distribution system pipe
materials, such as iron and galvanized steel, and components such as hot water
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systems. Solders and various types of metal pipes may result in the introduction
of metals such as cadmium, antimony and silver into the drinking water.
e. Pipe loop studies cannot adequately model water quality changes occurring in
the distribution system such is variation in temperature, pH, chlorine and
chloramine residuals.
Because of these problems using the pipe-loop system, utilities wiE find their use to determine
optimal treatment very difficult at present,
f. The Committee recommends that the Drinking Water Research Division
continue its research with pipe loop tests to obtain data that can be used to
provide a better understanding of corrosion and corrosion control procedures.
The research should be extended to systems of increasing complexity, to better
simulate the full-scale distribution system, and to investigate the effects of
corrosion on increases in concentrations of metals such as cadmium, antimony
and silver in addition to lead and copper.
g. The research program should be conducted so that it will lead to good
procedures that can be used by utilities to optimize their corrosion control
treatment program. Thus, the pipe loop materials and the methods of
construction that are used should be standardized to provide data that are easier
to interpret. Also, short-term, small-scale tests, such as coupon tests and
procedures involving electrochemical methods, should be conducted in parallel
with the research on pipe loop systems in order to develop procedures that can
be used by utilities to optimize their treatment (see Section 3.2),
3.2 The Usefulness of Methods Other than Pipe Loop Tests
Several available corrosion test procedures have the advantages of simplicity,
timeliness, and low cost when compared to pipe loop tests. These features make them
attractive for the determination of optimum treatment procedures by utilities. The
relationships of these tests, such as gravimetric measurements made using coupons, and
electrochemical measurements of corrosion rate, relate to the concentrations of lead, copper
and other metal ions that appear in drinking water after it passes through distribution systems
are not known. Metal ion concentrations are influenced by solubility and other factors in
addition to corrosion rate; therefore, these concentrations may not be directly related to
corrosion rate. The results of these simpler measurements should be correlated to the resulting
concentrations of metal ions, especially lead and copper, if they are to be used in corrosion
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studies relating to the lead and copper rule, If these methods are useful, using them rather
than pipe loop tests will be of great economic benefit to the water industry.
a. The Committee recommends that studies be undertaken to determine whether
the concentrations of lead, copper and other rrietals that enter water as a result
of corrosion are directly related to the measures of corrosion rate that are made
using gravimetric ind electrochemical methods. These studies should be
conducted in conjunction with pipe loop tests and studies of full-scale systems.
3.3 Standard Protocol for Evaluating Corroslvity
The measurement of the corrosivity in drinking water is a complex problem.
Historically, this has been accomplished using a variety of techniques. This variation in
technique has made the comparison of corrosivity and the effectiveness of corrosion control
measures between systems difficult, if not impossible, Therefore, using a standard protocol
for corrosivity measurements as a surrogate for metal content in drinking water is essential to
transfer results of corrosion.
The selected protocol must be simple and produce data in a timely fashion or it will not
be used. Furthermore, the criteria for evaluating candidate protocols must include the
relationship between the surrogate and copper and lead concentrations,
a. The Committee recommends that the search for a standard protocol should be
undertaken starting with the simplest test, gravimetrie-either with iron or lead
test systems, moving on to more complex approaches if this is unsuccessful,
b. The candidate protocol should be evaluated in "corrosive" and "non-corrosive"
waters in the field, correlating the surrogate data to actual copper and lead
concentrations.
3.4 Identification and Consideration of the Relative Severity of the Secondary Impacts
of Corrosion Control Procedures
Several secondary impacts of corrosion control procedures have been identified and
discussed in "Lead Control Strategies" written by Economic and Engineering Services, Inc.
and published in 1990 by the American Water Works Association (AWWA) Research
Foundation, Denver, CO, These include:
a. higher rates of trihalomethane (THM) formation by free chlorine at higher pH,
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b. lower disinfection efficiency of free chlorine at higher pH,
c. precipitation of CaCO3 if the pH or alkalinity is raised above the level of CaCOj
stability, and
d. higher aluminum solubility at higher pH if pH is raised before clarification with
alum is complete.
Each impact must be considered each time corrosion control treatment is implemented.
If the effect is too severe, the corrosion treatment procedures will have to be modified, or
additional changes in treatment will be required to reduce the impact. Also, optimal corrosion
control measures for one plumbing material may not be optimal for other types. For example,
if orthophosphate or zinc orthophosphate inhibitors are used, phosphate may cause
eutrophication of receiving waters if it is not removed by the wastewater treatment plant, and
zinc concentration in wastewater sludge may exceed some discharge limits from sewage
treatment plants.
An issue not discussed in the AWWA Research Foundation report concerns the use of
lime (CaO) to increase the concentration of calcium and pH. The addition of calcium is
suggested as one approach that can be used to control the concentration of lead and copper in
drinking water. The addition of lime is common, but can be an operational problem and can
affect water quality, especially turbidity. For example, addition of lime early in a treatment
plant may cause high residual aluminum concentrations because of aluminum solubility
relationships. Addition of lime just before the filter can cause difficulties with filter operation,
and addition after the filter can cause turbidity in the finished water and deposition of solids in
the distribution system. If common calcium salts are added instead, such as CaG2 or CaSO4,
Cl* and S04~ concentrations that are too high may result in some waters. Addition of lime at
wells that now only chlorinate also can cause turbidity and operational problems.
e. The Committee recommends that studies be undertaken to determine how lime
can be added to meet the goals of the lead/copper rule, and at the same time,
eliminate the operational problems associated with adding it.
3.5 Recommended Changes in Current Research Program Direction
The current research program is small but is dealing with important issues related to
distribution system corrosion and implementation of the lead and copper rule. Several issues
are not being addressed, however. A majority of the lead in first-draw water from brass
faucets results from corrosion of the lead-containing brass, and very little is known about how
to effectively control this type of corrosion. Similarly, the banning of lead-tin solder has
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resulted in the use of several new types of flux and solder, including solders containing various
percentages of antimony, tin and silver,
a. The Committee recommends that research on the corrosion of brasses and the
variety of available solders be undertaken to determine effective control
procedures.
The oxidation state of corrosion products in pipe scales may change depending upon
water composition and extent of stagnation of water in the pipe. Lead and copper speciation
and solubility may be affected by the oxidation state, and the change in oxidation state during
stagnation. The current research program includes some investigation of the composition of
scales and the Committee is of the opinion that this work should be continued and expanded.
b. The Committee recommends the research involving investigation of the
chemical composition of scales be continued, and expanded to determine the
changes in the nature of the scale that occur during stagnation periods, the
relationship of these changes to both water composition, and the concentration
of metals that dissolve in the water.
Microbiological processes are known to be occurring in full-scale water supply
systems. A major effect of these processes can be the alteration of surface features in pipes.
Some of these features are changes in adsorptive capacity of the wall, changes in local
oxidation potentials in the scale, and changes in the chemistry of the deposits as well as the
boundary film. These changes can also affect the diffusion of metallic ions into the stream of
water. Very little knowledge of the role bacteria play in most corrosion problems is available.
c. The Committee recommends that a study of the effect of microbes on corrosion
in distribution systems be undertaken, including their effect on corrosion of
iron, lead and copper.
Many water quality parameters can affect corrosion processes. One parameter that
could be important is the concentration of organic matter of different types. Organic
substances may complex metal ions, thereby increasing their solubility, may adsorb on
inorganic crystals, thereby affecting crystal growth and the solubility of the corrosion scale,
and may serve as substrate for microorganisms, thereby increasing the problems related to the
effect of microorganisms on corrosion.
d. The Committee recommends that research be undertaken to determine the
effects of organic compounds that can be present in drinking water on
corrosion.
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Many of the corrosion problems experienced in the United States are problems that
exist in other countries. One example is the lead corrosion problem in the United Kingdom.
U.S. EPA corrosion researchers should obtain and make use of information that has been
developed in these countries in order to minimize the amount of research that must be done in
the United States.
e. The Committee recommends that a program be established whereby the U.S.
EPA researchers can learn of the effectiveness of corrosion control procedures
that have been used in other countries and their applicability to situations in the
United States.
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4. CONCLUSIONS AND RECOMMENDATIONS
The Committee was pleased with the research program that was presented. In the
preceding section, we have made a number of recommendations based upon our evaluation of
the material presented during the May 9-10, 1991 meeting. The recommendations of the
Committee are summarized below,
a. That the Drinking Water Research Division continue its research with pipe loop
tests to obtain data that can be used to provide a better understanding of
corrosion and corrosion control procedures. The research should be extended to
systems of increasing complexity, to better simulate the full-scale distribution
system, and to investigate the effects of corrosion on increases in concentrations
of metals such as cadmium, antimony and silver in addition to lead and copper.
b. That the research program should be conducted so that it will lead to good
procedures that can be used by utilities to optimize their corrosion control
treatment program, Thus, the pipe loop materials and the methods of
construction that are used should be standardized to provide data that are easier
to interpret. Also, short-term, small-scale tests, such as coupon tests and
procedures involving electrochemical methods, should be conducted in parallel
with the research on pipe loop systems in order to develop procedures that can
be used by utilities to optimize their treatment.
c. That studies be undertaken to determine whether the concentrations of lead,
copper and other metals that enter water as a result of corrosion are directly
related to the measures of corrosion rate that are made using gravimetric and
electrochemical methods. These studies should be conducted in conjunction
with pipe loop tests and studies of full-scale systems,
d. That the search for a standard protocol should be undertaken starting with the
simplest test, gravimetric-either with iron or lead test systems, moving on to
more complex approaches if this is unsuccessful. The candidate protocol should
be evaluated in "corrosive" and "non-corrosive" waters in the field, correlating
the surrogate data to actual copper and lead concentrations.
e. That studies be undertaken to determine how lime can be added to meet the
goals of the lead/copper rule, and at the same time, eliminate the operational
problems associated with adding it.
10
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f. That research on the corrosion of brasses and the variety of available solders be
undertaken to determine effective control procedures.
g. That the research involving investigation of the chemical composition of scales
be continued, and expanded to determine the changes in the nature of the scale
that occur during stagnation periods, the relationship of these changes to both
water composition, and the concentration of metals that dissolve in the water.
h. That a study of the effect of microbes on corrosion in distribution systems be
undertaken, including their effect on corrosion of iron, lead and copper.
i. That research be undertaken to determine the effects of organic compounds that
can be present in drinking water on corrosion,
j. That a program be established whereby the U.S. EPA researchers can learn of
the effectiveness of corrosion control procedures that have been used in other
countries and their applicability to situations in the United States.
11
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