Design and Loading Factors for
Anaerobic Fermentation Plants
Arthur M. Buswell
Champaign, Illinois
The term "trade wastes" as ordinarily used applies to the water-
carried wastes discharged by manufacturing plants. It is the purpose
of this paper to discuss certain biological processes which, broadly speak¬
ing, are applicable to the stabilization of all organic wastes. A few of
these waste liquors carry mineral salts or acids which are responsible
for more or less damage to the stream. By far, the larger number dis¬
charge organic material of a biological origin, which on decomposing
causes putrefactive odors and a depletion of the oxygen of the stream
below the requirements of normal fauna and flora. It is obviously
this latter class of wastes with which we are primarly concerned in
the discussion of biological process in industrial waste treatment.
The primary object of treatment processes is to prevent oxygen
deficiency in streams. Oxygen deficiency is the basic cause of nuisance
and destruction of fish and other aquatic life, including normal vege¬
table life. The elements carbon and hydrogen and, to a small extent,
nitrogen are the chemical factors responsible for consumption of dis¬
solved oxygen; so the problem is to remove substances containing un-
oxidized compounds of these elements.
Bacteria of various sorts are capable of accomplishing this in two
ways, by forming either (a) relatively insoluble gases or (b) solids from
the carbon in the organic matter. These processes might be classified
as fermentative or gas-producing, and precipitating (bio-precipitation),
respectively. A more common classification of the processes for bio¬
logical stabilization is made on the basis of the classes of bacteria and
other microorganisms which are responsible for the results produced.
This classification divides the stabilizing processes into the aerobic and
anaerobic groups; that is, those produced by organisms requiring air
or oxygen and those carried on in the absence of oxygen.
Except in the case of very simple substances like acetic acid or glu¬
cose, aerobic and anaerobic action both yield solid and gaseous end
products under practicable conditions. When carried to the extreme,
the solids may be almost if not quite completely gasified by both
processes.
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