United States
                   Environmental Protection
                   Agency
Municipal Environmental Research -
Laboratory
Cincinnati OH 45268
                   Research and Development
EPA-600/S2-83-056  Oct. 1983
SERA         Project Summary
                   Seattle Distribution  System
                   Corrosion  Control Study:
                   Volume IV. On-Site  Evaluation of
                   Corrosion  Treatment

                   Carlos E. Herrera, Karen S. Nakhjiri, and Brian P. Hoyt
                     The Seattle, Washington, Water De-
                   partment conducted an 8-month pilot-
                   plant study on the treatment of Tort
                   River water with lime and sodium car-
                   bonate to prevent pipe corrosion. Pipe
                   loop tests were conducted with the
                   following objectives: (1) to determine
                   the appropriate chemical startup pro-
                   cedures for two full-scale corrosion
                   treatment facilities, (2) to document
                   the effectiveness of the corrosion treat-
                   ment program in suppressing corrosion,
                   metal leaching, and tuberculation in
                   older, galvanized-steel premise plumb-
                   ing systems, (3) to document the ef-
                   fects of the corrosion treatment pro-
                   gram on bacteria in water, and (4) to
                   anticipate any possible customer prob-
                   lems caused by implementing the cor-
                   rosion treatment program.
                     The study monitored the effects of
                   simulated corrosion treatment startup
                   on chemical and microbiological water
                   quality from an old galvanized plumbing
                   system. Standing water samples col-
                   lected after treatment startup displayed
                   increased iron deposits, organic debris,
                   and bacterial populations compared
                   with untreated standing-water samples.
                   Zinc leaching was reduced during treat-
                   ment at pH 6 to 7 and increased at pH 7
                   to 8. Iron leaching increased by approxi-
                   mately 38% during treatment startup,
                   whereas copper and lead leaching were
                   reduced by 53% and 57% respectively.
                   Corrosion treatment also reduced the
                   tuberculation rate by about 32%.
                     Based on this pilot study, a full-scale
                   corrosion treatment schedule is recom-
mended that minimizes possible water
quality problems caused by implemen-
tation. The recommended approach in-
cludes the gradual addition of lime and
sodium carbonate to a final treatment
pHof8.3.
  This Project Summary was developed
by EPA's Municipal Environmental Re-
search Laboratory. Cincinnati. OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).

Introduction
  The Seattle Water  Department serves
an average of 161 MGD of high-quality
water to nearly 1  million persons in the
greater Seattle area The water originates
in the Cascades from two mountain sources
- the Cedar and Tolt Rivers. The watersheds
are well protected, and the water requires
only disinfection with  gaseous chlorine to
meet Federal standards. The Cedar River
system, developed in 1901,  serves about
two-thirds of the area;  the remaining third
is served by the newer Tolt supply. These
mountain waters, which are predominantly
rainfall and snowmelt  runoff, are very soft
and  tend to be highly corrosive  to the
unlined metallic pipes in home plumbing
systems. Corrosion of the plumbing sys-
tems and the associated water quality
degradation has been  a major concern of
the Seattle Water Department for many
years Corrosion  has  caused aesthetic,
economic, and health problems. This sum-
mary discusses these problems and an

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  Customer complaints of aesthetically
undesirable rusty water,  red- and  blue-
stained  fixtures, and metallic tastes are
frequently received from within the Cedar
water distributrion system. These problems
have been documented by accurate com-
plaint records and by a questionnaire sur-
vey conducted by the Seattle Water De-
partment in 1973. The survey, which was
distributed to 1096 of all service  units
within the direct service area, showed that
16.7% of customers in the Cedar water
distribution system experienced corrosion-
related problems.
  Piping corrosion in the premise plumbing
systems served by the Cedar supply also
places a significant economic burden on
the homeowner. The average estimated
life span  of hot water galvanized and
copper pipes is approximately 35 years.
The average annual cost forecast in 1 978
for maintaining serviceability in these pipes
is estimated to be approximately $4 million.
  Studies performed from 1972 to 1976
demonstrate that the levels of lead, copper,
and iron in overnight-standing Cedar tap
water often exceed the levels defined by
the National Interim Primary Drinking Water
Regulations and the National Secondary
Drinking Water Regulations Cadmium and
zinc  also increased after standing  over-
night in home plumbing,  but they  rarely
exceeded permissible levels. These metals
originate from the copper and galvanized
pipes and the solders used in home plumb-
ing systems. Though the health impact of
metal contaminants in overnight-standing
water is not an acute problem, it is certainly
desirable to reduce exposure where possi-
ble.

Causes of Corrosion
  The corrosiveness of Cedar water results
from several related factors, including:
  •  Acidity, as indicated by low pH (the
     raw Cedar water pH is approximately
     7.6; after chlorination and fluoridation,
     pH is reduced to 6.8 to 7.2);
   •  Dissolved oxygen concentration at
     saturated conditions;
  •  Insufficient calcium and bicarbonate
     alkalinity in the water to form protec-
     tive calcium carbonate films on pipe
     surfaces;
  •  A relatively high [halogen + sulfate]/
     alkalinity ratio of 0.5  to  0.8 that
     results  in  conditions  favorable to
     pitting corrosion.
  In  1970, three factors combined to
intensify the corrosiveness of this  water
supply.  First, the chlorine dosage at the
open distribution  reservoir outlets was
increased to decrease the occurrence of
positive bacteriological samples within the
distribution systems. Second, ammoniation
of the water supply was stopped at the
request of the U.S. Public Health Service
to enable a free chlorine residual to be
maintained throughout the distribution sys-
tem. This change from combined to free
chlorination was implemented to provide
quicker, more effective disinfection of the
unfiltered water supply. The third factor to
intensify  the corrosiveness of the water
supply was the implementation of fluorida-
tion  with hydrofluosilicic acid in 1970
after a vote of the Seattle citizens in 1968.


Internal Corrosion Study
  In December 1975, the City of Seattle
retained a consulting engineering firm to
perform a detailed analysis of the corrosion
problem and to recommend possible solu-
tions. The Internal Corrosion Study, which
included  a 9-month pilot-plant investiga-
tion, confirmed the corrosiveness of Seattle
water, the causes of corrosion, and the
impacts  associated with the  corrosive
water, and evaluated alternative measures
to reduce the corrosiveness of the water
supply. The latter included changing the
methods of disinfection and fluoridation,
blending the water supply with ground-
water supplies, and adding corrosion-in-
hibiting chemicals.
  Based  on the findings of this study, an
Internal Corrosion Control Management
Plan was developed. Because the very low
levels of  mineral solids, pH, and  alkalinity
constitute the major causes of the water's
corrosiveness, this plan was designed to
correct the natural deficiency of minerals
in Seattle's water through chemical addi-
tion.
  The  consultant recommended water
quality goals using various chemical com-
binations that included the addition of lime
and sodium bicarbonate. The actual selec-
tion of chemical combinations and optimum
dosages  became the task of the Seattle
Water Department.
Tolt and Cedar Pi lot-Plant
Studies
  The Tolt and Cedar pilot-plant studies
were conducted  in  1979-80 to define
precisely the chemical treatment and dos-
ages needed for corrosion control in both
water supplies, and to document further
the effects of such treatment.
  These studies recommend the addition
of lime only to the Cedar supply and lime
plus sodium carbonate to the Tolt supply
for internal corrosion control.  The  treat-
ments were designed to achieve the water
quality characteristics listed in Table 1.
Study Objectives and  Scope of
Work
  The objectives of this research were as
follows:
  1. To determine appropriate  chemical
     startup procedures for the Tolt and
     Cedar full-scale corrosion treatment
     facilities,
  2. To document the effectiveness of the
     corrosion treatment program in sup-
     pressing  corrosion, metal  leaching,
     and tuberculation in older galvanized-
     steel premise plumbing systems,
  3. To document the effects of the cor-
     rosion treatment program on bacteria
     in water, and
  4. To anticipate any possible customer
     problems caused  by implementing
     the corrosion treatment program.
  From January 1981  to August  1981,
tests designed to simulate corrosion treat-
ment startup were conducted at the City of
Seattle Fire Station No. 35. This test site
was chosen  because  it contains  older
galvanized plumbing that experiences
severe corrosion-related waterquality prob-
lems. Also, the test site was located in the
Tolt distribution system because  the
changes in water quality caused by corro-
sion treatment will be greater there than in
the Cedar distribution system.
  The  corrosion  tests  documented  the
effects of corrosion treatment startup
based  on metal  leaching,  bacteriological
water quality, aesthetic water quality, and
pipe tuberculation. Running-water samples
and 24-hr-standing samples were collected
from an 8.5-m  pipe  loop system. The
samples were collected before treatment
(to establish baseline data) and during the
simulated treatment startup.
Operation, Results, and
Evaluation
  The pilot test apparatus consisted of a
chemical feeding and mixing system and a
1.9-cm-diameter old galvanized pipe test
loop (Figure 1).
  The pipe loop system was made from
10-year-old galvanized hot-water pipe col-
lected from the University of Washington.
When the pipe loop was installed, it was
highly tuberculated. The pipe loop was 8.5
m long and contained five elbows. Pressure
test gauges were located at the beginning
and end of the loop to determine headloss
in the loop. A flow of 10.5  L/min was
maintained through the loop using a throt-
tling valve at its end. Also at the end of the
loop was a flowmeter. The throttling valve
was periodically shut off to collect 24-hr-
standing samples.

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Table 1.    Present and Proposed Water Quality Characteristics
                        Present Quality of Chlorinated
                           and Fluoridated Water
                             Proposed Water Quality
                            After Corrosion Treatment
    Parameter
                           Cedar
               Tolt
                                                        Cedar
                                            Tolt
pH
Alkalinity (mg/LfCaCOJ
(Halogen + Sulfate)/
Alkalinity Ratio
6.8-7.4
15-18

0.5-0.8
5.8-6.2
2

2.5-4.5
7.8-8.3
20

0.5
7.8-8.3
14

0.5
   Throttling
               Pressure
               Gauge
        Flowmeter
To Drain
              Pressure
               Gauge
From Building
 Plumbing
                                                    To Building
                                                    Plumbing
                                                                        Static
                                                                        Mixer
                        1.9-cm-Diameter Pipe
                        Total length = 8.5 m
(a) Test Loop
                                            Static
                                            Mixer
                                                                      I Flowmeter
Figure 1.    Pilot plant flow schematic.


  The test treatment conditions were
chosen to simulate  average distribution
system levels of pH  and alkalinity during
full-scale treatment startup. Target water
quality for the test conditions appears in
Table 2.
  The effects of treatment startup were
determined from standing and  running
samples and headless determinations col-
lected from the test pipe  loop  system.
Standing water samples represented 24-
hr stagnant water conditions in the pipe
loop system. Running water samples were
collected after a 2-min flushing of the pipe
loop system at  10.5  l/min following the
collection of the 24-hr standing  sample.
The samples were  analyzed  for  metal
concentrations,  physical parameters, and
microbiological  quality before and after
corrosion treatment.  The microbiological
quality of the water and pipe incrustations
                                             Soda Ash    Lime
                                              Solution  Solution

                                             Ib) Chemical Feed System
               were examined with selective enrichment
               culture media and scanning electron micro-
               scopy. The chemical  composition of the
               tubercles and suspended paniculate mat-
               ter in the water were determined by x-ray,
               energy-dispersive microanalysis. Headloss
               in the test pipe loop system was used as an
               indication of pipe blockage.
                 The more frequently observed water
               quality changes occurring in the pipe loop
               before and after treatment were higher
               bacterial plate counts in 24-hr standing
               water than in running water (by two to
               three orders of magnitude), increased levels
               of iron concentrations, turbidity, and ap-
               parent color  in the  standing  water  as
               opposed to running water.
                 Standing-water samples collected after
               treatment startup displayed increased iron
               deposits, organic debris, and bacterial pop-
               ulations compared with untreated standing-
water samples. Iron-oxidizing and sulfate-
reducing organisms were shown to exist
within the pipe loop system in both the
standing water and tubercular incrusta-
tions. Opportunistic pathogens and coli-
form antagonists (including Pseudomonas
and  Flavobacterium)  were  detected in
standing-water samples and increased in
number with treatment startup. The public
health significance of sissile microbial
communities in drinking water was also
considered.
  In standing water, zinc leaching decreas-
ed during treatment at pH  6 to 7 and
increased at pH  7 to 8. Iron leaching
increased by approximately 3896  during
treatment startup, whereas copper and
lead leaching decreased by 53% and 5796
respectively.
  In running water, reductions occurred in
zinc and iron leaching during treatment
startup, and significant change was noted
in lead or cadmium leaching.
  Corrosion treatment reduced the tuber-
culation rate and subsequent pipe blockage
by about 3296.

Conclusions
  A full-scale corrosion treatment schedule
(Table 3) based on the test results was
recommended to minimize possible water
quality problems caused by the implemen-
tation of corrosion treatment The  recom-
mended approach was first to add lime
and sodium carbonate gradually to the Tolt
supply until the  pH equals that  of the
Cedar supply and then simultaneously to
add lime to the Cedar supply and sodium
carbonate to the Tolt supply to  a final
treatment pH of 8.3.
  The full report was submitted in fulfill-
ment of Grant No. R806686 010 by the
Seattle Water Department under the spon-
sorship of the U.S. Environmental  Protec-
tion Agency.        •    - -   -  - -

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  Table 2.   On-Site Test Treatment Conditions
        Item
                                                  Phase
                                                          III
                                                                       IV
pH
Alkalinity (mg/L CaCOJ
Lime Dosage, CaO (mg/L)
Na2C03 Dosage (mg/L)
6.00
2.0
0
0
7.00
9.0
0
7.42
7.60
8.0
2.00
6.40
8.00
14.0
1.70
9.00
  Table 3.    Corrosion Treatment Plant Startup Procedure for Tolt and Cedar Supplies

                          Total                                 Cedar
Day
1
8
15
29
42
Lime
Dosage
(mg/L CaO)
0.8
1.7
1.7
1.7
1.7
Sodium
Carbonate
Dosage
(mg/L Na2CO^
0
0
4.0
6.0
9.0
pH
6.3
6.6
7.1
7.5
8.3
Alkalinity
(mg/L CaCOj)
3.4
5.0
8.8
10.7
13.5
Lime
Dosage
(mg/L CaO)
0
0
0
1.0
1.7
pH
7.2
7.2
7.2
7.5
8.3
Alkalinity
(mg/L CaCOJ
16
16
16
17.8
19.0
     Carlos E. Herrera. Karen S. Nakhjiri, and Brian P. Hoyt are with the Seattle Water
      Department, Seattle,  WA 98144.
     Marvin C. Gardels is the EPA Project Officer (see below).
     The complete report, entitled "Seattle Distribution System Corrosion Control
      Study: Volume IV. On-Site Evaluation of Corrosion Treatment," (Order No. PB
      83-241 729; Cost: $11.50 subject to change) will be available only from:
            National Technical Information Service
            5285 Port Royal Road
            Springfield. VA 22161
            Telephone: 703-487-4650
     The EPA Project Officer can be contacted at:
            Municipal Environmental Research Laboratory
            U.S. Environmental Protection Agency
            Cincinnati. OH 45268
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