A NEW PROCESS FOR RECOVERING ACETIC ACID
FROM DILUTE AQUEOUS WASTE STREAMS
R. W. Helsel, Senior Environmental Engineer
Hydroscience Environmental Systems
Knoxville, Tennessee 37919
INTRODUCTION
The fact that significant changes in the world economy took place about two years ago
when the oil crisis hit is well known to everyone.   The cost of petroleum soared, and so
did the things that are derived from it, energy and chemicals.   The environmental control
scene also took on new perspective at that time.   Increasingly more stringent waste discharge criteria were being promulgated by regulatory agencies, and industry was faced
with the requirement to reduce its discharge of chemicals to the environment.   It was
only logical that environmental control activities be directed toward recovery processes.
Whenever detailed characterization of industrial wastewaters has been carried out, one
of the organic chemicals very commonly found in significant concentration is acetic acid
(Table I).   Depending on the source, acetic acid levels of Vi% to over 5% have been observed.   In some cases its presence is expected since it is used as a solvent or raw material, as in acetylation and esterification reactions.   But in many more cases its presence is
unsuspected, yet it is found as a by-product of various processes.   These include pulping
of wood, organic chemical syntheses involving oxidation, and petrochemical processes
which utilize severe conditions to crack or rearrange organic molecules or to recover them
from shale or coal.   When the thermodynamic stability of acetic acid is considered, and it
is recognized that acetic acid is a stable end-product of organic degradation reactions, its
wide-ranging occurrence in wastewaters becomes more understandable.   In fact, it is estimated that a significant portion of the acetic acid consumed by industry today could be
supplied by the acetic acid which is sewered or incinerated.
Table 1.   Sources of Acetic Acid in Industrial Wastewaters
Direct
Raw material (acetylation and esterification)
Solvent losses
Indirect (by-product)
Wood pulping
Oxidation reactions
Severe petrochemical processes (coal conversion)
Other chemical syntheses
THE NEED FOR ACETIC ACID RECOVERY
Advanced treatment of wastewaters containing significant levels of acetic acid to meet
uture water quality standards is being recognized as much more difficult to achieve than
MTVIOUslv thought.   When acetic acid undergoes biological oxidation, approximately one-
Jjalf of it is converted by the microorganisms to activated sludge.   This sludge tends to
nave poor settling characteristics and is difficult to dewater.   The high conversion to a
wet sludge makes ultimate disposal by incinceration expensive due to the large amounts
o  energy required.   Optimistically, sludge incineration   costs can be expected to be in
ne range of 4 to 6 tf/lb of acid.   Related to the need for adequate treatment, it should
be pointed out that acetic acid is listed in the proposed EPA regulation for hazardous
substances because of its environmental impact.
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