Odor Modification As Applied To Industrial Wastes
OSCAR B. LAUREN, Manager of Sales
Environmental Odor Control
Rhodia, Inc.
Hinsdale, Illinois 60521
PAUL M. FUGAMI, Regional Chief Chemist
Thompson Hayward Chemical Company, Inc.
Chicago, Illinois 60608
ODOR MODIFICATION
When two substances of given concentration are mixed in a given ratio, the
resulting odor of the mixture may be far less intense than that of the separate
components, and that eventually it may not be perceptible at all. This
phenomenon which is essentially a decrease of olfactory intensity can be
described as modification.
INTRODUCTION
Industrial expansion on which our economic position and standard of living depends,
creates increasingly complex problems where larger and larger volumes of gases and waste
effluents must be disposed of. The problem compounds itself not only because of the
necessity to clean up our air and water for aesthetic as well as health reasons, but also by the
pressures created by an increasing population —
— a population that is expanding to the very doorstep of wastewater treatment plants, pulp
and paper mills, feed lots and the like. Consequently, offending processes can no longer
operate in even solated areas with any real assurance that complaints won't arise.
The increasing awareness of the public and the increasing vigilance of the
Environmental Protection Agencies both tend to produce the general reaction that,
whenever there is an objectionable smell, something must be done about it. Where those
gases are toxic and present in sufficient concentration, they do, of course present a serious
health hazard. But there is also a second and larger group of effects which can result from
the odor concentrations, which though not toxic, are harmful to the comfort and well-being
of the community.
Let us first ask these questions: What is an odor or malodor? How do we detect it? Why
do responses to odor vary from person to person? We call substances odors physiologically
if, when they are presented to the nose at or above some threshold level, they cause change in
the activity of the receptor cells and cells higher in the olfactory pathway. Psychophysical^
we call substances odors if we perceive them as an odor, or if we can demonstrate
behaviorial responses to the substances when they act on the olfactory receptors. As the
interaction of the stimulant molecule and the chemoreceptive membrance cannot be
monitored on the molecular level, knowledge of the extramental odor world is necessarily
based on introspective psychophysical judgements or behaviorial responses of
experimental animals. THUS FROM THE HUMAN POINT OF VIEW A SUBSTANCE
HAS AN ODOR IF ONE CAN SMELL IT. In a still rather elusive way the nature and
strength of odor are related to some selected molecular or bulk properties of odorants,
which presumably are accessible to object measurement. The complex mechanism of man's
response to an odorous stimulus is not yet well understood. It is known that both
physiological and psychological changes occur. Some of these changes are transitory and
others, such as adaptation are more lasting and influence response in not readily predictable
ways.
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