However, not all filters effectively eliminate lead. Look for ones that are specifically certified by NSF International, the Public Health and Safety Co., to do so. Formerly the National Sanitation Foundation, NSF is a respected non-governmental, nonprofit organization based in Ann Arbor, Mich., that develops national standards and certifies water filtration systems for manufacturers and regulatory agencies (www.nsfconsumer.org).
In order to be NSF-certified to reduce lead, a filter is "challenged with solutions containing 150 ppb" and must remove at least 95 percent of it, says Rick Andrew, technical manager for the NSF Drinking Water Treatment Unit Certifi- cation Program.
Besides the rigorous testing, "NSF also reviews all packaging and product literature to make sure the product lives up to the manufacturer's claims."
To find NSF-certified products, go to www.nsf.org/certified/dwtu and search by manufacturer, model number or the type of "reduction claim" such as lead, chlorine and so on.
Among filtration systems that meet NSF's standards are widely available pitchers and larger-capacity countertop dispensers by Brita and Pur. These "pour-through" systems use GAC cartridges and sell for between $20 and $50; replacement filters can cost around $50 a year, although they are cheaper by the dozen.
Depending on how much tap water your household uses, refilling a pitcher or dispenser manually gets old fast -- especially if you use the water not only for drinking but also for making pasta, coffee or infant formula.
Later this year, Brita plans to introduce a stand-alone water cooler that filters water directly from a water line instead of using cumbersome bottles. Brita says its new three-gallon unit costs one-third that of bottled water a year after taking into account the $39.99 filters that must be replaced every 150 gallons or six months.
Faucet-mounted filters screw onto a faucet -- usually replacing the aerator installed immediately above it -- and typically use a diverter to direct water through the system when treated drinking water is desired. (Washing dishes with untreated water is considered safe because the lead is diluted and the drying eliminates potential lead residue, says Andrew of NSF. However, he suggests using filtered water when brushing teeth because ingesting "any lead is bad.")
Larger "plumbed-in" systems that connect directly to a water line can be hidden under the sink and usually require professional installation. Some, such as the Culligan SY-2500 ($180) use a carbon block filter. Others, including the MacGuard by Kinetico ($199), use reverse osmosis -- where water is forced under high pressure through a semi-permeable membrane to screen out dissolved solids -- which is generally quite effective in reducing lead.
However, reverse osmosis systems have several drawbacks.
They're pricey -- from $200 to $1,600 -- take up a lot of room and may
filter out such beneficial ions as calcium and fluoride.
------------------------------
City to Try Chemical To Reduce Lead Levels
Three-Month Test Is Planned in NW
By D'Vera Cohn
Washington Post Staff Writer
Sunday, February 29, 2004; Page A12
Federal and D.C. officials are planning a three-month
trial in part of the city of a chemical that they hope will reduce alarming
lead levels in drinking water. If all goes well, they hope to begin using
it Sept. 1 throughout the water system serving the city and parts of Northern
Virginia.
The chemical is likely to be an orthophosphate, which forms a protective coating on pipes to prevent lead from leaching into water. It is widely used across the country as a standard treatment to prevent lead contamination.
"It's a chemical problem that can be corrected chemically," said Thomas P. Jacobus, general manager of the Washington Aqueduct's two water treatment plants that serve the District, Arlington and Falls Church.
Officials have not figured out why lead levels in the drinking water of thousands of D.C. homes suddenly tested above federal contamination limits over the past two years, but they said they do not need to know that to fix the problem of lead leaching off pipes.
The strategy was designed by a hastily convened committee of engineers, chemists and water-system experts. It would require approval by the Environmental Protection Agency, which is considered likely since EPA scientists serve on the committee. Water system officials hope to announce their plan March 10, refine it with laboratory tests and study and release a detailed implementation strategy May 1.
"I'm not at all convinced it would fix it," said Michael Marcotte, chief engineer for the D.C. Water and Sewer Authority. But he said he is encouraged that the group of outside experts thinks it is the best shot.
The proposed schedule calls for adding orthophosphate to the water supply in one section of the city on June 11, tentatively a swath of upper Northwest Washington. The neighborhood, which is north of downtown, includes numerous older homes with lead service pipes.
The three-month trial will not be long enough to test whether the chemical will reduce lead levels.
Jacobus said some utilities have had success within a few months, but others have waited 18 months or more.
Its main purpose is to see whether adding the chemical causes other problems, such as rusty water, dark water, bad tastes, odors or skin problems. Although it's widely used nationwide and is considered safe, each water system's chemistry is unique and can be affected differently by the chemical.
The Fairfax County Water Authority has been using zinc orthophosphates since 1998 and saw little change in the water's taste, odor or color, spokeswoman Jeanne Bailey said.
Jacobus said the effort would be relatively inexpensive:
about $600,000 to install equipment and $600,000 a year for the chemicals.
The cost "wouldn't even be seen on the water bill of the customer, it's
such a small amount," he said.
--------------------------------
WASA, Army Corps Were Told of Threat in 1994
By Carol Leonnig and D'Vera Cohn
Washington Post Staff Writers
Sunday, February 29, 2004; Page A01
The D.C. Water and Sewer Authority and the Army Corps of Engineers rejected warnings from consultants who said as early as 1994 that lead contamination was a serious threat because of the way the two agencies were managing the water supply, according to records and interviews.
Addressing the problem a decade ago would have required changing the water treatment plan by adding phosphate, at the time estimated to cost more than $870,000 a year. But WASA and the Corps, the owner and operator of the Washington Aqueduct, resisted the change in part because it was deemed too expensive, according to a consultant's report and interviews with officials involved in the decisions.
"It looks like operator incompetence," said Jim Elder, who from 1990 to 1995 was the director of the drinking water program at the Environmental Protection Agency. "They knew what to do for years, and they didn't take the basic steps to protect the public, even when the problem was obvious."
Other cities that have lead service pipes and faced a similar predicament switched to phosphates and largely avoided contamination, among them Chicago, which has the highest concentration of lead pipes in the nation. But in Washington, the prediction of a consultant in the mid-1990s began to come true three years ago, when tests first revealed alarming levels of lead in the water.
Another consultant and a WASA official warned that the spike in lead in 2001 and 2002 was a sign that the pipes were corroding and leaching lead.
WASA officials said they rejected the change in water treatment because they believed it was a costly and unproven remedy. The Corps officials, who are responsible for delivering high-quality drinking water, said they also did not act because neither their customers nor federal regulators asked them to.
On Friday, three weeks into a public health scare that affects at least 23,000 households and has caused widespread concern and confusion, Corps officials said they hoped to begin testing a new water treatment plan June 1. The solution, first advanced a decade ago and now used by nearly half of the utilities in the country, requires introducing phosphates into the water, which experts say will render the system less corrosive and eventually control lead contamination.
But for the foreseeable future, WASA and the Corps will have to deal with the consequences. Of the 6,118 tests WASA conducted last summer, more than 4,000 came back with lead levels above the federal limit of 15 parts per billion. About 157 homes had water with lead levels of more than 300 parts per billion, a toxic content so high that it has astounded water quality experts.
Exceeding the federal levels has dire consequences for WASA, which must now replace lead service lines until the contamination is under control. A decade ago, when federal regulators imposed this condition, they assumed it would serve as an expensive and seldom-invoked measure for cities that did not take the threat seriously. Now WASA is planning to spend millions of dollars to replace lead pipes.
Thomas Jacobus, who has been director of the Washington Aqueduct since late 1994, noted that EPA regulators never raised concerns about the water management. He said WASA and the two municipalities in Virginia it serves, Arlington and Falls Church, were reluctant to accept the added costs of changing the water treatment plan.
"We didn't make a change because . . . we just didn't," Jacobus said in an interview last week. "We were confident in our plan. If we could go back in time, sure we would have acted sooner."
Marc Edwards, an environmental engineer at Virginia Tech in Blacksburg and an authority on corrosion control, said the EPA should have anticipated Washington's lead contamination. The federal agency oversees water treatment and distribution in the District and Wyoming, the only such arrangements in the country.
"They're all acting like this is all some totally new thing that just came up," Edwards said of the water's corrosiveness. "If you consider the warnings that EPA has been given over the years about changes in treatment and their impact on plumbing systems, this public health crisis is not unexpected."
Edwards said he fears that the District has had a serious and hidden lead problem in its water for many years, one that went undetected by required tests. He said he was astounded in March 2003 when his own tests, taken from closer to the water main, revealed unusually high lead levels.
"I was scared stiff, " he said. "We could have been missing the problem for a long time."
Cost Concerns
Treating water to make it safe became a more challenging
task in 1991, when the EPA implemented a sweeping new rule that required
all water utilities to test for lead and copper, both toxic to humans,
especially young children. The EPA also required large utilities to do
extensive water studies to determine the best way to control the water's
corrosiveness, which can scrub and leach lead and copper off pipe linings,
surfaces and fittings.
ECG Inc., an environmental consultancy based in Vienna, was hired in 1994 by the Corps to conduct the required tests at two treatment plants, Dalecarlia on MacArthur Boulevard and McMillan near Howard University. The consultants found that adding lime to water, as the Corps was doing, was "consistently worse" in curbing lead corrosion than the alternative: zinc orthophosphate. On a scoring range of 0 to 7 -- with 7 the best -- lime scored 3 and zinc orthophosphate scored a 6.
The ECG study, dated June 1994, nevertheless recommended that lime be used, noting in part that phosphates would cost more for water treatment and sewage treatment. The consultants said that if costs were not a problem, "it is recommended" that the Corps turn to phosphates.
ECG noted that the treatment plant's customers also raised concerns. WASA, which was then part of the District government and since 1996 has been a quasi-independent agency, argued that phosphates would significantly increase costs at its sewage treatment plant and make disposal of sludge more expensive. Michael Marcotte, the chief engineer for WASA, said last week that it potentially could cost millions of dollars to remove the phosphate that will be sent to the Blue Plains sewage treatment plant.
The aqueduct's Virginia customers, Arlington and Falls Church, also resisted adding phosphates because both had very little lead in their pipes and consequently no lead problem to solve. WASA, Arlington and Falls Church also worried that their sewage treatment plants might flush more phosphates into the Chesapeake Bay and affect its fragile ecosystem.
"We prefer that we not receive additional phosphorus," Lawrence Slattery, chief of Arlington County's water pollution control division, said last week. "We can handle it, but there are additional costs and there also are additional environmental impacts."
Instead, the consultants crafted a plan for the Corps to continue adjusting the water chemistry by adding lime, which makes the water less acidic.
At the EPA's Region III office in Philadelphia, which is responsible for the District's compliance with environmental regulations, officials decided to hold off on approving the Corps corrosion plan because of other pressing problems: In 1995 and 1996, toxic bacteria in the water had violated federal limits. The Corps continued to use lime and received interim approval from the EPA in 1997 and final approval in 2000.
As recently as two years ago, after WASA's own tests revealed high levels of lead, the EPA's regional office again endorsed the original water treatment plan, according to a May 2002 letter written by George Rizzo, the EPA official responsible for the District's drinking water.
Marcotte, who joined WASA in 1997, said he was not aware of the 1994 recommendations. He acknowledged that his team's ability to manage the lead problem may have been affected by other crises facing WASA at the time. The agency, overhauled and newly independent, was "hampered to the degree that we did not have a lot of history in this system and not a lot of background."
Richard A. Rogers, a top water official in the EPA's regional office, said the federal agency hired experts who initially recommended phosphates. There was a consensus, Rogers said, that using lime might be safer because phosphates could stimulate bacteria.
But Elder, the former EPA director, said it was "unbelievable" that the regional office approved the so-called "pH adjustment" using lime for an older city with extensive lead in its pipes.
"I don't know how that could have been approved," he said. "The [EPA] rule and the science warned that pH adjustment alone was probably not going to do the trick to control lead. Plus, Region III must have known that the District was filled with lead service lines."
Jon M. Capacasa, the EPA's director of water protection in the regional office, and Michael Schock, the agency's leading expert on corrosion control, both stressed last week that there are tradeoffs with every chemical. Without more conclusive research, they said, none is considered a magic solution.
Changing Chemistry
Controlling bacteria in the water supply, as the mid-1990s
revealed, is a delicate science. It is also a regulated one. In November
2000, the Corps switched from using chlorine in its disinfection process
at the aqueduct and instead introduced chloramines, a combination of chlorine
and ammonia. Use of chlorine was no longer feasible because it produced
high levels of cancer-causing byproducts.
But in making the switch, the Corps ignored the EPA's written guidelines warning that a significant change in disinfection treatment could increase lead corrosion. The EPA recommended that utilities carefully monitor the possible effects of chloramines.
The American Water Works Association Research Foundation, the scientific division of the trade group, noted in a survey in 1999 that high doses of chloramines appeared to increase corrosion. But the Corps did not conduct studies on corrosion because no one raised it as an issue, said Jacobus, the general manager of the treatment plants.
Rogers, the regional water manager at the EPA's regional office, said other utilities were not experiencing any problems in switching to chloramines, among them a utility in California that served as a model for Washington. Federal rules gave the EPA's regional office the authority to require testing the impact of chloramines on corrosion, but Rogers said that did not appear warranted.
"At the time, there was no information to suggest chloramines could cause a problem with corrosion," he said. "Of course, now we see we need to look at all possibilities of impact on corrosion."
Jacobus said he agreed that the switch to chloramines may have helped trigger the current lead contamination but added that there is no conclusive proof.
"Through the whole process, none of our staff or EPA or our consultants said we need to study the effect of chloramines," he said.
Calls for a Switch
Tests by WASA revealed high levels of lead in the summer
of 2001 and continued to flag a problem through the summer of 2002. The
utility's water quality manager, Seema Bhat, urged a change to a less corrosive
water treatment plan.
Bhat, who has received whistleblower status and is also suing WASA, said in an interview that Marcotte told her in September 2002 that he did not want to use phosphates because of the higher costs associated with treating sewage.
According to internal e-mails provided by Bhat, she tried to persuade Marcotte and other WASA officials by arranging a seminar with a phosphate company in October 2002. Bhat said neither Marcotte nor other top WASA officials attended the seminar.
Marcotte said he recalls telling Bhat that a switch to phosphates "wasn't a decision to be made lightly." He and Rogers, the EPA's regional water manager, said more study was needed before launching a change in water treatment.
The Corps, which performs the required testing of the city's tap water, knew there were elevated levels of lead in 2001 and 2002. But the treatment plants did not consider changing their water chemistry because they were never asked to do so, Jacobus said.
Marcotte, asked why WASA took no action, said the Corps never proposed a change.
"I'm confident we're going to solve it," Jacobus said of the lead contamination. "It's true that what solves the problem now could have solved it two years ago. But we can't go back in time."
Staff writer David Nakamura contributed to this report.
© 2004 The Washington Post Company
---------------------------------
The natural lead levels in water are low. A study of
raw surface waters(8) found only 20 percent had detectable lead levels,
although the mean concentration of the detectable samples was 23 µg/L.
Groundwater, which is generally more alkaline (basic) than surface water,
has an even lower natural lead content(15). The solubility of lead
is 10,000,000 µg/L at low pH (5.5) and 1 µg/L at high pH (9.0).
Most of the problem with public water supplies is related to lead that
is leached by low pH (acidic) water from service connections, lead pipes,
and soldered joints.
---------------------------------------------
When drinking water is the source of lead, a significant
amount of lead is absorbed by the body. The estimated mean daily absorption
of lead from drinking water is 3-10 µg. The cumulative exposure from
food, air, and water can result in lead absorption surpassing 50-60 µg
per day, the limit at which there is no observable health effect .(8,12)
Risk to children
The total lead exposure level of 50-60 µg lead
per day for which there is no observable health effect applies to adults.
Children absorb 40-50 percent of ingested lead, as opposed to 5-10 percent
absorption by adults. Because water intake per kilogram of body weight
is higher in children than adults, contaminated water is a greater risk
to youth. The U.S. Environmental Protection Agency (EPA) estimates that
the average drinking water contribution to total lead intake for a 2-year-old
child is 20 percent. Infants on formula receive even higher percentages
of lead intake from drinking water. Atmospheric exposure to the lead from
automobile emissions increases with proximity to the ground, another hazard
for children. A 2-year-old's estimated daily intake of lead from food (100
µg), air (18 µg), and water (70 µg) can be as high as
190 µg per day, substantially more than that estimated for adults(8).
Young children have the added exposure to lead from flaking paint, particularly
those from families in older urban housing.
--------------------------------
on Lead:
Over the past two decades, a number of federal efforts
have focused on reducing the public's exposure to lead. Because an estimated
20% of the average American's exposure to lead is through drinking water,
the United States Environmental Protection Agency (USEPA) has made it a
priority through recent regulations to reduce lead in potable water. The
most recent mandate is the "Lead and Copper in Drinking Water Rule" (LCR).
In 1992, to meet LCR requirements, the city began monitoring lead and copper
levels at a number of Boulder residences.
------------------------------
Are phosphates new?
No. Over half of all water utilities across the country
use some sort of corrosion control to comply with the Lead & Copper
Rule. Many cities in the USA and Canada use phosphates. Zinc orthophosphate
is presently being applied successfully in systems in Hawaii County and
on Wake Island. Phosphoric acid is used at the Big Island Volcanoes National
Park, in New York City, Milwaukee, Cleveland, Atlantic City, and Charleston.
Why does the Maui DWS have to use phosphates in the Upcountry
system?
Water utilities in the USA are required to comply with
the Enviromental Protection Agency's Lead and Copper Rule. This rule was
passed in 1991 and sets the action level for lead in drinking water at
15 parts per billion (ppb). This means that utilities must ensure that
water from the customer's tap does not exceed this level in at least 90%
of the homes sampled. If the water from the tap does exceed the limit,
then the utility must take steps to correct the problem.
How much phosphate is added to the water?
We add 1.11 milligrams per liter of phosphoric acid at
the three Upcountry water treatment facilities. The phosphate residual
(P) in the water system is about 0.3 milligrams per liter (mg/L). Compare
this to soft drinks, which contain up to 7.8 mg of phosphorous per ounce.
Does the phosphate work in controlling the lead in customers'
plumbing?
For the most part, yes. According to the State Department
of Health Safe Drinking Water Branch, the 90th percentile calculation shows
that for the August 2003 monitoring period for the Makawao System, the
lead and copper levels were below the action level triggers. The 90th percentile
lead concentration was less than five parts per billion and the 90th percentile
copper concentration was 0.1 parts per million. (The action level for lead
is 15 parts per billion and the action level for copper is 1.3 parts per
million.)
The Lower Kula System also passed at 10.6 ppb for lead.
However, the Upper Kula System did not pass - the 90th percentile was 41
ppb. We are doing additional testing on this system to verify the results.
-----------------------------------
2. Water Chemistry: The specific characteristics of the
water in contact with the materials influences the length of time it takes
for the components to passivate.
a. Corrosiveness of water, including pH, velocity
of flow, chlorine level, temperature, and dissolved oxygen.
b. Presence of corrosion inhibitors such as orthophosphate-based
chemicals.
---------------------------------------------
Corrosion:
Analysis of film formation using phosphate inhibitors
in systems with various water qualities. Friedman,
Robert Mark; Cortez, Enriqueta; Liu, Jingyue; Pacholec, Frank; Lechner,
John B.; Dwyer, James J. Analytical Sciences Center,
Monsanto Corporate Research Monsanto Co., St. Louis, MO,
USA. Proceedings - Water Quality Technology Conference
(1996), Volume Date 1995, (Pt. 2), 2405-2433.
CODEN: PWQCD2 ISSN: 0164-0755. Journal written in English.
CAN 128:299260 AN 1998:306417 CAPLUS
Abstract
Stringent Federal limits on Pb and Cu concns. in drinking
water have generated increasing interest in the use of blended phosphates
as heavy metal corrosion inhibitors in potable water delivery systems.
These additives result in the formation of passivation layers or protective
films on the metal surfaces which significantly reduce the Pb and Cu concn.
measured at the tap. Water systems located in different geog. regions
or from different types of supply have widely varying water quality properties
which will influence the efficacy of treatment. To address this issue,
we have investigated metal test coupons exposed using a corrosion rack
to water from sources of varying water quality ranging from high to low
hardness and alky. with differing pH values. The compn., chem. identity,
thickness, rate of formation and uniformity of the films formed were studied
using a variety of phys. and chem. methods designed to give a more complete
understanding of the passivation process. Anal. techniques included
Electron Spectroscopy for Chem. Anal. (ESCA), IR microspectroscopy and
secondary electron microscopy. Alternative phosphate treatments,
the effects of other concurrent water treatments and the use of different
coagulants will also be discussed with regard to the integrity of the phosphate-based
passivation layers. The anal. results will be discussed with regard
to performance measured by corresponding Pb and Cu analyses of water samples
taken at the tap and in the pipe loop.
Indexing -- Section 61-8 (Water)
assive films
Water distribution systems
(anal. of passivation film formation
using phosphate inhibitors in systems with various water qualities)
Phosphates, uses
Polyphosphates
Role: TEM (Technical or engineered material use); USES
(Uses)
(corrosion inhibitors; anal. of passivation
film formation using phosphate inhibitors in systems with various water
qualities)
Water purification
(corrosion prevention, ortho/polyphosphates;
anal. of passivation film formation using phosphate inhibitors in systems
with various water qualities)
Corrosion inhibitors
(ortho/polyphosphates; anal. of passivation
film formation using phosphate inhibitors in systems with various water
qualities)
-------------------------------------
Pilot plant and laboratory evaluation of corrosion inhibitors
for mixed surface and groundwater systems. Ryder,
Robert; Yeager, Tom; Russick, Kathy. Kennedy/Jenks Consultants,
San Francisco, CA, USA. Proceedings - Water
Quality Technology Conference (1993), (PT. 2),
1507-43. CODEN: PWQCD2 ISSN: 0164-0755. Journal
written in English. CAN 121:212547
AN 1994:612547 CAPLUS
Abstract
Tests conducted on highly differing surface and groundwater
sources that are frequently mixed by diurnal and seasonal demands showed
that low Zn (1:5 ratios) are as effective for corrosion inhibition of Pb
and Cu as 1:1 or 1:2 Zn ortophosphate ratios. Elevation of pH to
7.7 and ortophosphate corrosion inhibitor is nearly as good as Zn ortophosphate.
Silicate-ortophosphate blends are less effective for most waters.
A long exposure time is necessary to discern corrosion redn. by blended
ortophosphate inhibitors. Zn concn. in water can be lowered by >2/3
and will reduce wastewater discharge by more than half. Cu concn.
in water can be lowered by 40-80% and in wastewater discharge by 25-35%;
Pb concns. can be lowered below action limits for both surface and groundwater
by ortophosphate addns.
Indexing -- Section 61-8 (Water)
Water purification
(corrosion prevention, corrosion inhibitors
for mixed surface and groundwater systems)
7439-92-1, Lead, properties
7440-50-8, Copper, properties
Role: PRP (Properties)
(corrosion inhibitors for mixed surface
and groundwater systems)
--------------------------------
Evaluation of corrosion inhibitors in drinking water
supply systems. Panu, U. S.; Martin, C. W.
Department of Civil Engineering, Lakehead University, Thunder
Bay, ON, Can. Editor(s): Singh, V. P.; Al-Rashed, M.;
Sherif, M. M. Proceedings of the International Conference
on Water Resources Management in Arid Regions, Kuwait, Kuwait, Mar. 23-27,
2002 (2002), 4 289-310. Publisher: A. A. Balkema,
Rotterdam, Neth CODEN: 69DVDG Conference written in English.
CAN 139:122347 AN 2003:328618 CAPLUS
Abstract
The problem of corrosion has existed for as long as metal
pipes have been used for the transportation of drinking water. Although
the problem was originally mostly related to bad tasting or discolored
water, in recent times water quality has become a focal issue in preventing
adverse medical effects. In Canada, guidelines to protect consumers
are set forth by the Federal-Provincial Subcommittee on Drinking Water
of the Federal-Provincial Committee on Environment and Occupational Health.
To ensure adherence to these guidelines, the City of Thunder Bay (Ontario)
conducted a corrosion study of its drinking water supply systems.
The study tested four chem. corrosion inhibitors while monitoring concns.
of 26 metals. However, the study was focused on six metals, viz.,
lead, copper, aluminum, iron, manganese, and zinc. The study seeks
out answers to three specific questions. The first is which of the
four corrosion inhibitors worked best within the Thunder Bay water supply
systems. Second was the nature of the potential existence of relationships
between the concns. of the six metals to each of the four corrosion inhibitors.
Third were investigations into causal effects of natural changes within
the water system on the corrosion inhibition process. An anal. of
data sets on metal concns. arising due to various corrosion inhibitor treatments
was also able to indicate that caustic soda was able to produce the most
significant overall redns. in metal corrosion. Addnl. statistical
analyses of the data set confirmed that caustic soda is the best choice
for mitigating corrosion within the water supply system of Thunder Bay.
Of the remainder three corrosion inhibitors, the polyphosphate was also
found to perform well in reducing corrosion rates, while the sodium silicate
and zinc orthophosphate were found to have marginal benefits. Investigations
on the relationship that may exist between metal concns. for a given corrosion
inhibitor treatment process led to some useful information.
While there were a few strong relationships when
corrosion inhibitor treatments were viewed sep., the iron and manganese
showed a strong correlation during all four corrosion inhibitor treatments.
The four system indicators (namely, pH, alky., temp., and chlorine) play
varying roles of importance in the corrosion process in water supply systems.
While the effects of pH and, to a certain extent, alky. are limited, the
temp. and chlorine are shown to significantly impact the corrosion rates
experienced within the Thunder Bay water distribution systems.
-----------------------------------
Phosphate inhibitor use at US utilities.
McNeill, Laurie S.; Edwards, Marc. Utah Water Research
Laboratory, Utah State University, Logan, UT, USA.
Journal - American Water Works Association (2002), 94(7),
57-63. CODEN: JAWWA5 ISSN: 0003-150X. Journal written
in English. CAN 137:268050 AN 2002:533302
CAPLUS
Abstract
Surveys of US drinking water utilities were conducted
in 1994 and 2001 to investigate trends in phosphate inhibitor use.
More than half of those water providers surveyed reported adding phosphate
inhibitors to their water. Zinc orthophosphate and polyphosphate
were commonly used inhibitors, and a shift from poly/orthophosphate blends
to orthophosphate was obsd. from 1994 to 2001. Inhibitor doses ranged
from <0.2 to >3 mg/L as PO4 (although many utilities could only report
dosages "as product" because of the proprietary nature of the inhibitor
chems.). Surprisingly, most utilities based their inhibitor selection
on limited information, with smaller utilities relying more on nontech.
information (e.g., vendor information, success of the chem. at another
utility) than on direct confirmation of the inhibitor's effectiveness.
Many utilities are aware of potential drawbacks of inhibitors, esp. increased
biol. activity and more treatment costs and residuals.
Indexing -- Section 61-8 (Water)
Water purification
(corrosion prevention; phosphate inhibitor
use for lead and copper corrosion prevention at US utilities)
Polyphosphoric acids
Role: NUU (Other use, unclassified); USES (Uses)
(zinc salts; phosphate inhibitor use
for lead and copper corrosion prevention at US utilities)
7439-92-1, Lead, processes
7440-50-8, Copper, processes
Role: CPS (Chemical process); PEP (Physical, engineering
or chemical process); PROC (Process)
(phosphate inhibitor use for lead
and copper corrosion prevention at US utilities)
7779-90-0, Zinc orthophosphate
Role: NUU (Other use, unclassified); USES (Uses)
(phosphate inhibitor use for lead
and copper corrosion prevention at US utilities)
Supplementary Terms
drinking water phosphate inhibitor USA
-----------------------------