Structural Determinants in the
Oxidative Breakdown of
Aliphatic Compounds by Domestic
Activated Sludges
GEORGE W. MALANEY, Professor Microbiology
and
ROBERT M. GERHOLD, Research Assistant
Department of Microbiology and Water Resources Center
The Ohio State University
Columbus, Ohio
The objectives of this study were (a) to determine the relative amount of
BOD removal which can be attributed to oxidation of organic molecules in the
aeration tank during conventional detention periods, and (b) to point out patterns of oxidation as related to the structure of the compounds attacked. This
study was restricted to a consideration of the aliphatic compounds.
Although much data are available on the oxidation of individual chemical compounds as obtained by the conventional dilution BOD method, few
studies have been made on the oxidative abilities of activated sludges from
aeration tanks of domestic treatment plants in operation. Results of this study
furnish information related to the ability of unacclimated activated sludges to
oxidize individual aliphatic organic compounds. The results also suggest when
acclimation of initially-resistant compounds may be expected within short
periods of aeration.
MATERIALS AND METHODS
The experimental method used in this investigation involved exposure of
the activated sludge microflora to individual aliphatic compounds in the Warburg constant temperature respirometer with measurement of oxidation in
terms of oxygen uptake.
In order to get a reasonably reliable picture of the capacity of activated
sludges to handle organic substrates, the problem of representative sampling
of the sludge had to be considered. It was decided that treatment plants used
as source of activated sludge should vary as much as possible in size, design,
and type of influent waste. Three treatment facilities near Columbus were
selected: (1) the municipal plant for Columbus, (2) the municipal plant for
the village of Hilliard, Ohio, and (3) the plant for the Brookside Estates, a
subdivision near Linworth, Ohio. The first two plants are conventional activated sludge plants, while the Brookside plant is a small "aerobic digestion"
(total oxidation) unit.
The sample of activated sludge mixed liquor was collected on the day the
Warburg run was to begin and was prepared immediately for analysis. The
number of microorganisms added to each Warburg flask was standardized arbitrarily by adjusting the suspended solids in the mixed liquor to a concentration of 2,500 mg/1.    The sludge was not washed.    No mineral salts were
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