THE INFLUENCE OF MUNICIPAL WATER
DISINFECTANTS ON TEMPRITE®,
CHLORINATED POLY(VINYL CHLORIDE)
PIPE AND FITTING COMPOUNDS
ANDY OLAH, SENIOR R&D ASSOCIATE,
GROUP LEADER- EXTRUSION
POLYMER ADDITIVES AND SPECIALTY PLASTICS
THE BF GOODRICH COMPANY
Recently there has been increased
interest in the influence of various types' of water disinfectants in
public water systems upon the long term performance
of the materials comprising both municipal water distribution systems
and hot- and cold-water plumbing systems. These piping materials
include: polyethylene,
poly(vinyl chloride), polybutylene, polypropylene, crosslinked
polyethylene and chlorinated poly(vinyl chloride). It is suspected that
municipal water disinfectant additives such as chlorine, ozone, hydrogen
peroxide, chlorine dioxide and bromine increase the oxidation reduction
potential (ORP) which reduces
the oxidative stability of certain plastic materials comprising both
public and private water distribution systems.
The oxidation reduction potential or ORP
is a more accurate characterization of the disinfectants influence on
certain plastic piping material, than is the level
in parts per million (ppm) of the disinfectant chemical. Furthermore,
the ORP used by water treatment facilities can relate both water pH and
the disinfectant level. That is, the ORP and not the
oxidizer/disinfectant concentration reflects the
degree of oxidative degradation certain plastic piping materials may
undergo. Over twenty-five years ago the World Health Organization (WHO)
reported in its
Standards for Drinking water that an ORP of 650 mV provides disinfection
and viral inactivation almost instantaneously. Therefore, it is felt
that an ORP of
between 750 to 800 mV would be sufficient for a long-term test medium
for determining long-term performance of plastic piping materials for
water
distribution systems.
This work reports on chlorinated
poly(vinyl chloride) pipe and fitting materials which have been
conveying high ORP water systems for both municipal water
treatment systems and also at elevated temperatures in private hot- and
cold-water distribution systems for over forty years.
This work will cite both work generated
at The BFGoodrich Company relative to environmental exposure of CPVC
compounds to high ORP water solutions
and also call on case studies of pipe and fittings made from TempRite
CPVC resins and compounds in industrial applications where the ORP of
the fluid
media are extremely high.
TempRite chlorinated poly(vinyl chloride)
(CPVC) compounds comprise primarily chlorinated poly(vinyl chloride)
resin derived by a post polymerization, chio-
rination process upon poly(vinyl chloride) (PVC) resin. One major
aspect of this process is that the working temperature of CPVC will be
higher than that of PVC.
Other ingredients in CPVC compounds are relative to providing to the
final product impact strength, elevated temperature stability for the
processing (melt
forming) step, flow enhancers for the processing step and color pigments
for final product appearance. TempRite CPVC compounds have many
end use applications but two end uses that are relevant to demonstrating
the oxidative stability are the industrial piping application (CORZAN)
and the hot- and
cold-water distribution or plumbing application (FlowGuard® and
FlowGuard Gold).
Since it's commercialization in the early 1960's, the CORZAN industrial
piping segment of the TempRite Division has been concerned with the
influence of dif-
ferent chemical environments on the long-term performance of the GPVC
pipe and fitting materials. To better understand this performance
numerous che-
mical resistance tests have been conducted under both static and
stressed conditions to determine the performance of CORZAN materials for
various end-
use applications. These tests demonstrate that CPVC pipe and fitting
compounds are not negatively affected by contact with chemicals used in
municipal water treatment. For example, CPVC has been found to be
unaffected by saturated chlorine-water solutions (0.3%, 3000 ppm),
hydrogen peroxide (30%), sodium hypochlorite (15%), chlorine dioxide
(0.1 %) and hypochlorous acid. Furthermore, these environments have been
demonstrated acceptable for
handling by CPVC at elevated concentrations far above those found in
treated municipal water. This information has been substantiated by
in-depth laboratory testing and publicly conveyed by the distribution of
these chemical resistance data.
CPVC materials are commonly used in
industrial fluid handling applications. Many of these applications are
in both drinking water treatment and wastewater
treatment. Other industrial applications involve handling those
chemicals used in municipal water disinfection at extremely high levels
in general chemical process applications. For example, in one industrial
installation, Corzan CPVC pipe and fittings are employed in two
different elevated temperature lines conveying 31% hydrochloric acid,
and 12% sodium hypochlorite. In another application, Corzan
CPVC pipe and fittings are used in a wastewater treatment facility
handling extremely high levels of chlorine dioxide. Corzan CPVC pipe and
fittings are
used in handling chlorine in a chloralkali process and also in an
industrial facility handling chlorine and sodium hypochlorite. All these
applications and installations demonstrate that pipes and ftting made
from TempRite CPVC resins and compounds can withstand extremely high
oxidation reduction potentials regularly and over long periods of
time. In fact, one of the benefits of CORZAN CPVC is its corrosive
resistance especially in industrial applications where
the fluid environment is extremely corrosive to the conventional metal
piping systems applicaffons. These environments are in fact high
levels of chlorine,
hydrogen peroxide, chlorine dioxide and sodium hypochlorite; many of the
same chemical environments used at much lower levels are used as
disinfectants in municipal water treatment.
Chlorinated poly(vinyl chloride) plumbing
products (FlowGuard® and FlowGuard® Gold™) were first
introduced in the late 1950's. Many of these early systems
are still in use today. They are continuously handling many different
types of water and water quality in both municipal, public water systems
and private sys-
tems. These CPVC materials have never demonstrated a deficiency relative
to the water source, the water treatment chemicals nor the water
treatment system.
There has never been a region of the country nor a municipality where it
has been brought to the attention of BFGoodrich that the water quality
has compromised the performance of these CPVC materials.
Finally, recent studies have shown that
the negative influence of these water treatment environments on plastic
piping materials can be described by a speci-
fic physical-chemical mechanism. Furthermore, this mechanism is specific
to plastic materials where oxidative degradation is a long-term
performance
concern. These materials include the polyolefin family of plastics,
which is comprised of polyethylene, crosslinked polyethylene,
polybutylene and polypro-
pylene.
These materials, in fact, incorporate
antioxidants into their final compound to offset their natural tendency
to undergo oxidative degradation. Chlorinated
poly(vinyl chloride) pipe and fitffng compounds do not undergo oxidative
degradation. In fact, as the end use performance and chemical resistance
aspects demonstrate, the additives used to disinfect municipal water
systems have no negative effect on chlorinated poly(vinyl chloride) pipe
and fitting mate-
rials.
Recent concerns are well founded
regarding the negative influence that municipal water disinfectant
chemicals can have on certain plastic piping materials. It is true that
high ORP water systems can shorten the long-term performance polyolefin
pressure pipe materials. It is also true that chlorinated poly(vinyl
chloride) pipe and fitting plumbing materials such as FlowGuard and
FlowGuard Gold are not affected by these water additives. In fact, CPVC
materials have demonstrated under chemical resistance testing as
environmentally resistant to these chemicals. Furthermore, CPVC
industrial piping systems handle these same chemical environments
regularly and at much higher concentrations than the levels found in
municipal drinking water. After forty years of FlowGuard and FlowGuard
Gold plumbing installations neither the short-term nor the long-term
performance have ever been compromised by the potable water conveyed.
TempRite, FlowCuard, FlowCuard Cold and Corzan
are registered trademarks of The BFGoodrich
Company.
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