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CHAPTER 12

ION EXCHANGE

APPLICATIONS IN
WATER TREATMENT

Michael C. Gottlieb
ResinTech, Inc.
West Berlin, New Jersey

INTRODUC~ON

Ion exchange processes are widely used in water and wastewater treatment to remove ob-
jectionable ionic contaminants. The nature of ion exchange, as used by industry, has
changed dramatically over the last 80 years. The first ion exchange processes used inor-
ganic zeolites mined from natural deposits as a cation exchanger for water softening. Mod-
em synthetic polymer-based exchange media are today used as cation and anion ex-
changers. They have largely displaced the natural zeolites, primarily due to higher
capacities, except in specialized applications. By the mid-1990s, in response to more strin-
gent discharge limits and pending implementation of tighter potable water guidelines, there
was increased development activity of ion exchanges with high selectivities for specific
substances. Some of these are organic-based and others are inorganic-based.
Ion exchange processes primarily treat waters with low mineral content, to reduce un-
desirable ionic contaminants. By far, the largest single application of ion exchange is in
softening. Softening is the process of removing calcium and magnesium ions from water.
Ion exchange is widely used in the power and utility industries to produce softened or
demineralized water and in-home water softeners. The use of ion exchange in these ap-
plications has been widely practiced for several decades and is well defined.
Since September 11, 2001, a greater awareness of possible terrorist threats to potable
water systems has created new challenges for water treatment operators. So-called "dirty
bombs," made from conventional explosives and packed with radioactive substances, are
of concern because they can spread radioactive substances to public water supplies. For-
tunately, ion exchange technology already exists to remove these substances and some of
the poisons that may have to be dealt with. A separate section on terror is included, de-
scribing the most likely substances to be involved. The individual treatment approaches
for their removal will be listed separately according to the substances themselves.
Ion exchange is also used in many specific applications, for example, to reduce or re-
move potentially harmful ionic contaminants from potable water supplies in chemical pro-

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