tea
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-023  Mar 1981
Project Summary
Field  Test of  Corrosion
Control  to  Protect
Asbestos-Cement  Pipe
Gary S. Logsdon
  This research program was initiated
to determine whether adding zinc
orthophosphate  to  potable  water
would sufficiently coat an asbestos-
cement  pipe with zinc to prevent
asbestos  fibers  from entering  the
water.
  Storage tanks and chemical and
feed pumps were set up at each of the
Greenwood,  SC, water treatment
plants, and zinc orthophosphate was
fed into the system at an average rate
of 0.3 mg/L. Two sections of new
asbestos-cement pipe were installed
to represent a low-flow  and a high-
flow   water condition;  they  were
removable for testing. Samples were
periodically tested to determine  the
number  of  asbestos fibers  in  the
water. The two  pipe sections were
removed  and  examined  for  the
amount  of  zinc deposited on  the
surface.
  Although routine tests, such as pH
and alkalinity, showed no significant
changes  during  the  study period,
asbestos fibers in the water decreased
substantially. Electron  microscope
photographs and energy dispersive X-
ray spectra analyses showed coatings
of zinc  products on  the  two pipe
samples.  Thus,  adding  zinc ortho-
phosphate under the existing  water
quality conditions reduced or pre-
vented corrosion of asbestos-cement
pipe.
  This Project Summary was devel-
oped by the EPA's Municipal Environ-
mental Research Laboratory, Cincin-
nati, OH 45268, 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
  Asbestos-cement  (A/C) pipe has
been used in the United States since the
1930's Because this pipe does not rust
and cause "red water" or rusty water
problems for water users, some water
utilities  have  used  A/C pipe as an
alternative to cast iron when the treated
water has had a history of corroding cast
iron water mams. In some instances,
using A/C pipe to carry aggressive or
corrosive water has deteriorated the
A/C pipe.
  Zinc orthophosphate, developed as a
corrosion control  additive for  water
distribution  systems, has been used
successfully in the  1970's to control
problems of  corrosion  m cast iron
mams The Greenwood study was con-
ducted to evaluate its use for controlling
deterioration of A/C pipe exposed to
aggressive water  The pipe, much of
which had been installed in Greenwood
in the late 1940's and 1 950's, had been
attacked  by the water carried by the
pipes During the study, the water leav-

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         ing the treatment plant had a pH of 8 2
         to 8 3, alkalinity of 20 mg/L as CaCO3,
         total hardness of 10 mg/L as CaCO3,
         and an iron content of 0.1 mg/L. As the
         water  passed through  the A/C pipes,
         the  pH increased—an indication  that
         constituents of the A/C pipe were being
         dissolved by the water.
          Methodology
           After the  equipment was installed,
         zinc orthophosphate was injected into
         the system just ahead of the clearwell at
         each of the two treatment plants, begin-
         ning on October 11,  1977. The initial
         feed rate for passivation was 3 0 mg/L.
         The passivation period was ended after
         3 days on October 14, 1977, short of the
         intended date of October 15, because of
         problems  encountered at one of the
         system's larger users, a pharmaceutical
         company.  This  firm,  which processes
         gauze  and surgical supplies,  used a
         cotton-filament, wound filter to remove
         rust or iron  particles as well  as other
         particles in the water. The high concen-
         trations of zinc orthophosphate clogged
         the filters sufficiently for the company to
         change filters every 2  to 3 days during
         the initial periods, normally,  a set of
         filters would have lasted 6 to 7 months.
         The feed rate was reduced to 0 5 mg/L
         in an effort to ease the filter problem
         When  zinc was found at 0.17 mg/L at
         the low-flow location,  it was concluded
         that zinc was present throughout the
         system.
           The clogged filter problem at the phar-
         maceutical company  continued  how-
         ever, and on November 21, the zinc feed
         rate was lowered to  0.3 mg/L.  The
         concentration  of zinc  at  the low-flow
         location  decreased to less than 0 1
         mg/L. This rate was continued until the
         end of the  study, although problems
         were still encountered with the filters.
           Water from two test locations (one
         high-flow, one low-flow) where A/C
         pipe is used, was routinely sampled for
         zinc content, pH, alkalinity, and calcium
         as CaCOs. Water samples werealspfor-
         warded  to  the  EPA  laboratory in
         Cincinnati to determine the number of
         asbestos fibers present.
           The  high-flow test site (a 20-cm (8-
         inch) A/C pipe servicing other mains in
         a subdivision) was selected because it
         represented a flow-through situation
         This location was about 1.7 km (1  mile)
         from one of the two treatment plants
         where zinc  was added. The low-flow
         sampling location (a 15-cm(6-mch) A/C
main) was on a looped dead end line
about 5  km (3 miles) from  the same
treatment plant
  At each of thetwosampling locations,
a section of new A/C pipe was installed
so that it could be removed at the end of
the experiment.
  Throughout  the  study period, water
quality was monitored at both locations.
When  the  water  had been  tested on
March 2, 1976, no asbestos fibers were
found in the well water but 022 x 106
fibers/liter were found  in water  that
had  passed through about  2 miles of
A/C pipe. The finished water had an
Aggressiveness Index (Al) of about 104
to 105  The tendency of a water to
deteriorate the structure  of  asbestos-
cement pipe has been described by the
Al as
tapping'
         Al = pH + log (AH)
where
    pH = -log a(-T (-log of the hydrogen
     ion activity)
    A  = total  alkalinity in  mg/L as
     CaC03
    H = calcium concentration in mg/L
     as CaCO3

  Waters possessing an Al >120 are
considered   to  be  "nonaggressive",
those where Al < 10.0 are  said to be
"highly" aggressive," and those with an
Al between 10 and 12 are "moderately
aggressive." During  the study, the Al of
the water at the closer, high-flow loca-
tion ranged from 10.6 to 11.2, which is
somewhat above the Al at the treatment
plant. At the  more distant, low-flow
location, the Al varied from 11 2 to 11 9
during the study—a  range considerably
higherthanthe  104 to 105AI values at
the treatment plant


Results
  After  the initial passivation period,
zinc concentration at the closer location
averaged about 0.2 mg/L; at the distant
location, it was generally less than 0.2
mg/L, averaging 0 1 mg/L These con-
centrations  were  not  sufficient to
prevent a  rise in  pH and calcium
between the two sampling  locations.
Most of the calcium  increase in  the
distribution  system  occurred  between
these sites, where  zinc concentration
was lowest
  Two times after A/C  pipe had been
tapped in  the sample  location vicinity,
high asbestos  fiber counts  were  ob-
served.  Because  pipe
operations  can temporarily  raise the
fiber count in the distribution system,
the use of tapping machines equipped to
flush away drilling and tapping debris is
recommended.
  The  scanning electron  microscope
(SEM) was used to examine the interior
pipe wall of pipe samples removed from
both sample locations. The interior sur-
face of the 20-cm  (8-mch)  pipe  was
smooth, and some coating  resulting
from zinc treatment could be identified.
The interior of the 15-cm (6-inch) pipe,
with a lower concentration of zinc (0.1
mg/L), had much larger uncoated areas
on the pipe surface.
  Regardless of which portion of the
pipe was examined, the 20-cm (8-inch)
pipe always  showed  better  coverage
than the 15-cm (6-inch) pipe. This indi-
cates that the zinc or zinc compounds do
adhere to the A/C pipe, and that to be
effective, the zinc concentration should
be 0 2 mg/L, or higher if possible
  Energy-dispersive,   X-ray   spectro-
metric  elemental analyses were made
on  the surfaces of the two test pipes,
these analyses were compared with
that for a new, unused piece of pipe. Orj
the unused  pipe, the only large peak
shown was calcium  High peaks were
seen for iron and zinc on the 20-cm (8-
inch) test pipe and the low peak seen for
calcium could indicate that t'ie pipe  is
well protected and the  calcium  is
masked at this location. High silica and
calcium peaks and a low zinc peak were
observed for 1 5-cm (6-inch) pipe at the
low-flow locatom. This again indicates
that the low zinc concentration of 0.1
mg/L in the 1 5-cm (6-inch) A/C pipe is
not adequate  to provide a protective
coating—certainly not as effectively as
the higher concentration (10.2 mg/L)a1
the other site.
  In  the  energy-dispersive,   X-ray
spectrornetric analyses, the  peak  size
for  zinc and iron varied with location ir
the pipe. A comparison of these peakj
from the 15-cm (6-inch) and the 20-crr
(8-inch) pipes showed, however,  tha
the highest peaks of the 20-cm (8-mch
pipe were always higher than the high
est  peaks of the 1 5-cm (6-inch) pipe, anc
the lowest peaks of the 15-cm (6-mch
pipe were always lower than the lowes
peaks of the  20-cm (8-inch)  pipe  Th<
results for the iron peaks suggest  tha
iron in the water provides a partial pro
tective coating to the A/C pipe in thi:
system.

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Conclusions
  The study results of using zinc ortho-
phosphate to  protect A/C pipe suggest
that this treatment will cause A/C pipe
to be coated  with  a  protective  com-
pound. A zinc concentration of 0.2 mg/L
was adequate to provide a coating on
the pipe wall, but pH  and  calcium
increases occurred  at this concentra-
tion of zinc The concentration of zinc
reaching the  end of  the distribution
system  should  exceed  0.2  mg/L.
Because zinc precipitates in the system,
the amount  of  zinc  orthophosphate
dosed at the treatment plant to obtain
the desired zinc residual would  have to
be determined for each system.
  The full report, submitted in fulfill-
ment of Grant No R804888-01 by Com-
missioners  of   Public  Works,
Greenwood, CA, under the sponsorship
of the  U.S. Environmental Protection
Agency, was  authored  by Clarence E.
Grubb
                                          Gary S. Logsdon is with the U.S. Environmental Protection Agency (see below).
                                          Ralph W. Buelow was the EPA Project Officer.
                                          The complete report, entitled "Field Test of Corrosion  Control to Protect
                                           Asbestos-Cement Pipe." (Order No. PB 81-152 878; Cost: $5.00, subject to
                                           change) will be available only from:
                                                 National Technical Information Service
                                                 5285 Port Royal Road
                                                 Springfield. VA  22161
                                                 Telephone: 703-487-4650
                                          Gary Logsdon. the present contact, can be  reached at:
                                                 Municipal Environmental Research Laboratory
                                                 U.S. Environmental Protection Agency
                                                 Cincinnati. OH 45268
                                                                                      I US GOVERNMENT PRINTINQ OFFICE 1961 -757-01Z/7016

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