Transcript Powerpoint - AL/MS Section of AWWA

Meeting the Lead and
Copper Rule Requirements
Alabama-Mississippi
AWWA Education Workshop
January 2014
Vernon L. Snoeyink
University of Illinois
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What should you expect from
this presentation?
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An understanding of the regulations
and health effects of Pb and Cu
A discussion of possible changes to the
Lead and Copper Rule (LCR)
Important concepts
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Scale formation and metal ion release
Scale stability and conversion issues
Constant pH stabilizes scale
Phosphate inhibitors reduce Pb solubility
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Copper Regulations
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Action Level (AL) is 1.3 mg/L (90th
percentile value)
AL samples: 1 liter first draw after 6
hours of stagnation
Basis:
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Health reference: prevent nausea
SMCL: 1.0 mg/L based on taste and
staining
Ref: Advances in Water Research, Oct-Dec 2013, vol. 23, no. 4.
Ref for Cu Corrosion: Chapter by Schock in Water Quality
&Treatment, 6th Ed. AWWA/McGraw Hill, 2011
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Copper Control
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In general, pH below 7 causes high Cu
Corrosion produces scale, and scale
solubility determines Cu concentration
Cu concentration depends on pH, type of
scale that forms, and alkalinity, and
whether the pipe is new
Low pH (~7 or less) and high alkalinity (~
300 mg/L as CaCO3) AL exceedance
Reduce Cu by increasing pH (if CaCO3
doesn’t precipitate) or orthophosphate
Ref: S. Grace et al. “Control of new copper corrosion in highalkalinity drinking water” JAWWA Jan. 2012
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Lead Regulations and Sources
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AL is 15 μg/L (90th percentile)
Lead service lines & lead/tin solder
outlawed in 1986
Brass fixtures in homes, meters, water
coolers etc.
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The LCR (1991) says Pb ≤ 8 %
As of Jan 2014: Pb ≤ 0.25% of wetted
surface of fixtures (2011 Safe Drinking
Water Act Amendment)
Proposed revision to the LCR expected
in 2014. Speculation only on what it
might include
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How does Lead Get Into
Drinking Water?
DC Water: From Source to Tap
Internal
Plumbing
Washington
Aqueduct
Treats Water
Treatment
Plant
Non-lead Service Line*
DC WASA
Distributes Water
to Residents
Water contains the same
low levels of lead as in the main
but may pick up low levels of lead
from water meters.
Main
Potomac River
Water in main ALWAYS contains
very low levels of lead (less
than 2 ppb)
When water
spends several
hours in the
internal plumbing
without moving,
it can absorb
(generally smaller)
levels of lead
from fixtures and
faucets.
Lead Service Line
When water spends several hours
in the lead service line without
moving, it can absorb lead from
the service line.
*A small fraction of homes have brass service lines that can also contribute low levels of lead.
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Health Effects of Lead
CDC: “No Safe Level”
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Health effects related to blood lead levels
(CDC: 5 μg/dL)
Infants and young children most susceptible
Primary source is lead paint dust
Neurological damage, impact on IQ, probable
human carcinogen (renal tumors in rats)
MCLG of zero
Brown, M. J.; et al. Association between children's blood lead levels, lead service lines,
and water disinfection, Washington, DC, 1998-2006. Environ Res 2011, 111 (1), 6774.
Brown, M. J.; Margolis, S. Lead in drinking water and human blood lead levels in the
USA. Morbidity and Mortality Weekly Report 2012, 61(Suppl; August 10, 2012),
1-9.
Wat. Qual. &Treat., 5th Ed, Amer Wat. Works Assoc. , McGraw Hill, 1999
Edwards et al. ES&T Jan 27, 2009
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The Presence of Lead Hurts
Public Confidence
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Good Housekeeping, Feb. 2005 issue
Pb in water usually comes
from Pb scales
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Pb  Pb2+ + 2e (corrosion)
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Pb scales:
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Electron acceptors: O2, HOCl, OCl-, NH2Cl
Lead carbonates: PbCO3 & Pb3(CO3)2(OH)2
Lead phosphates: Pb3(PO4)2 & Pb5(PO4)3OH
PbO2 may also be formed if free chlorine is
used in the distribution system
Non-crystalline lead solids and non-lead
solids may be important
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We have 3 alternatives for
using water quality to control
Pb
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Use orthophosphate, PO4, pH 7.2-7.8
Use pH 9 -9.5 with an alkalinity > 35
mg/L as CaCO3
Use free chlorine to form PbO2
The diagram on the next slide can be
used to explain these options
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pC-pH Diagram shows pH range
of low solubility
Schock, USEPA
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Elemental Distribution – Chicago, IL
Red Color is proportional to element density
Note the location of most of the lead
BSE Image
Si
Al
Ca
Fe
Mn
P
Pb
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Washington, D.C.
Change from secondary
disinfection with free chlorine
to monochloramine led to
severe LCR violation
Refs:
• EPA website
• Schock and Giani, Proc Wat Qual
Tech Conf, San Antonio, Nov 2004,
Amer Wat. Wrks Assoc., Denver
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2001 – 2002 Lead AL was
exceeded
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90th percentile was 75 ppb)
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The Washington Aqueduct (WA) treats
Potomac River water and sells it to
Washington DC, Arlington County and
Falls Church.
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DC WASA (now DC Water) is responsible
for meeting the AL
WA is responsible for treating water
Arlington Co and Falls Church never
exceeded the AL
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Lead Service Lines
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DC Lead Compliance History
Schock and Giani, 2004
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PbO2 rapidly converts to Pb2+
when free chlorine is changed
to NH2Cl
Very likely:
Pb0 is the electron donor
 PbO2 is the electron acceptor
Pb0 + PbO2 + 4 H+ 2 Pb2+ + 2 H2O
 Product is Pb2+
 Reaction is very rapid IF
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PbO2 is in contact with lead pipe
Or if PbO2 is in outer layer and scale is
conducting
PO43- must
be present to convert Pb2+ to
scale, to prevent high Pb concentrations
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Lead Profiles show that 1liter first-draw samples do
not give the highest lead
concentration
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Peak lead values occur in the
service line
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NH2Cl
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Free Cl
Schock and Giani, 2004
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Water Quality Affects Scale
Properties. Keep pH constant
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At Washington Aqueduct, variable pH:
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7 to 8.5: high in winter, low in summer
Cause: post filter lime feed turbidity
Alkalinity: typically 60 mg/L as CaCO3 but
highly variable; high in summer
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Desktop Study Showed
1) High pH not an option
2) o-PO4 best
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CaCO3 precipitated above pH 8.5 but 9+
required
o-PO4 (H3PO4) likely best
Trial: apply to part of the distribution
system before full-scale
Recommended pipe loop study to
optimize treatment
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Full-Scale Implementation
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Elevated total coliform counts, but no
Coliform Rule violation
Colored water complaints in DC (1-2 a day).
Caused by the phosphate?
Unable to flush prior to implementation
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Lessons learned:
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Flush before implementation
Document quality before implementation
Announce implementation before actual change
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Pipe Loop Study Design
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Evaluate alternate control strategies
Use harvested lead service lines
Seven operating conditions, three loops
each (21 loops total)
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Loop 4 vs 6 show PO4 Effect
Figure 2-1: Effect of Adding a Phosphate Inhibitor on Total Lead Concentrations - Comparison of Racks 4 & 6
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Total Lead Concentration (ug/L)
= No Phosphate Inhibitor
= 3.0 mg/L Phosphoric Acid
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50
40
30
20
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0
2/17/05
Loop 4A
Loop 6A
3/30/05
5/10/05
Loop 4B
Loop 6B
Loop 4C
Loop 6C
6/20/05
7/31/05
9/10/05
10/21/05
12/1/05
1/11/06
Date
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Results of Pipe Loop and Full
Scale Study
No reason to use zinc
orthophosphate instead of
phosphoric acid as PO4 source
 Lowering the chloramine dose did
not reduce lead concentrations
 Application of 3.5 mg/L H3PO4 as
PO4 to the full scale system
achieved compliance in the 1st full
sampling period.
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Results of Pipe Loop and Full
Scale Study
Lead levels continued to decrease
as the PO4 dose was lowered from
3 to 1 mg/L (in pipe loop)
 No evidence of an effect of a
chlorine burn on lead levels after
conversion to a Pb(II) scale
 Lead concentrations are higher the
higher the temperature
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LCR Lead Compliance Data
PO4 feed started in fall 2004
at 3.5 mg/L as PO4
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What Is Occurring Because of
DC Experience
The“action level” has become a “de
facto” MCL
 Confidence of public in water
supply
 EPA taking closer look at LCR
 EPA examining LSL sampling times
(not just first draw)
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Chicago Case History
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Lake Michigan water, Alk ~ 100 mg/L,
Ca ~ 2 mM, Alum coagulation, free
chlorine, ortho plus polyphosphate
inhibitor
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Problem: phosphate forms a precipitate
with residual aluminum that increases
resistance to water flow in pipes
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Ref: Atasi et al., Proc AWWA Annual Conf., Orlando,
2004
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Aluminum Phosphate: Chicago
Case History
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1 mg/L as PO4 of an ortho-polyphosphate
blend is added to control lead release from
lead service lines
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Precipitation of AlPO4 forms fine particles
that deposited on walls of a 72” and a 90”
cement lined mains
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Residual Al in the summer is ~ 175 μg/L
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C-factor was reduced from about 135 to 95
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Recent Chicago Results
Del Toral et al, ES&T 2013
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LCR values for the last decade are ~6
ug/L
Peak values are service line samples
and are ~ 2xAL
LSL disturbances cause the highest
values (construction, LSL leak repair,
meter installation…)
Should the LCR be changed to base
compliance on the sample from the
LSL?
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Important remaining questions:
The service line problem
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Replacement of lead service lines poses
a serious problem.
Partial lead service line replacement of
questionable benefit and may worsen
the situation
Full service line replacement is costly
and especially difficult to mandate in
our old large cities
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Final Thoughts
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Lead in drinking water is an important
problem that will be with us for awhile.
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The low lead content requirement for
brass will help decrease the problem
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We will have to find some way to make
the lead service line problem go away
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