Chlorine Dioxide in Waste Treatment
R. N. ASTON
Technical Representative
Mathieson  Chemical   Corporation
Cincinnati, Ohio
Chlorine dioxide is not new to the industrial waste treatment
field inasmuch as it has been in use since 1944. Actually, up until
about two years ago its use in the field was confined primarily to the
treatment of potable water supplies. While one may say that water
is not an industrial waste in the usual sense, the applications pointed
the way to the more recent developments. The wastes in many of
the water supplies, particularly the phenolic type, could be smelled,
tasted and tested. The work in water treatment indicated the
power of chlorine dioxide to remove or oxidize phenols in the range
of parts per million or even parts per billion.
Chlorine dioxide is now in commercial use in several fields of
waste treatment for both gaseous and liquid wastes. Operating data
are available on the application of chlorite in the treatment of phenolic
wastes from several different industries. Plant scale studies are now
under way on the treatment of cyanide wastes with chlorite. Chlorine
dioxide is being used on a plant scale in the treatment and elimination
of obnoxious odors from plants that render animals and fish.
A brief review of the method of application of chlorine dioxide
will aid in an understanding of its use. Chlorine dioxide is a powerful oxidizing agent and exists normally as a yellow-red gas. It is
not sufficiently stable, however, to be shipped or stored as such. It
must, therefore, be prepared as needed at the point of application.
Technical Sodium Chlorite (NaClOo), a dry, stable chemical available commercially, serves as a most convenient source of supply. The
usual method of preparing chlorine dioxide for commercial use is to
react a solution of sodium chlorite with a solution of chlorine such
as produced by the usual commercial chlorinator found in industrial
plants or water purification plants. The chlorite solution is added
by means of a chemical proportioning pump to the chlorine solution
in a packed glass column known as a chlorine dioxide solution generator. This produces an aqueous solution of chlorine dioxide with
or without excess chlorine in solution depending on the ratios of
each fed according to the reaction:
2NaC102 + Cl2 -* 2C102 + 2NaCl
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