Digestion of Potato Waste Substances -
Laboratory Conditions
E. D. WAHL, Assistant Professor of Chemical Engineering
A.M. COOLEY, Professor of Chemical Engineering
G. O. FOSSUM, Professor of Civil Engineering
University of North Dakota
Grand Forks, North Dakota
The work described in this paper was part of a research effort entitled "Treatability Study of Potato Processing Wastes. " It was a three-year study sponsored by
the Public Health Service, Department of Health, Education and Welfare.
The work was carried out in three distinct parts 1) Determination of Rate of
Oxygen Uptake by Potato Substance,  2) Activated Sludge Treatment of Potato
Waste Media,   and 3) Study on Improvement of Rate of Digestion of Potato Waste
Media.
DETERMINATION OF RATE OF OXYGEN UPTAKE BY POTATO SUBSTANCE
Purpose
A study to determine the oxygen uptake rate of potato substance subjected to
various treatments was undertaken to provide greater understanding of the characteristics of the potato. In addition, it was hoped that the information obtained
would provide a guide to the oxygen requirements in the stabilization of plant
wastes receiving similar treatment (i.e., cooking, high pH).
Experimental Method
The experimental work was performed using the standard BOD test as outlined
in Standard Methods for the Examination of Water and Wastewater, 11th Edition.
Three major modifications were made to the test. First, samples were withdrawn at 1,2,3,4, 6, 7,10,13,16 and 20 days in addition to the regular five-day
test. Secondly, the dilution water pH was adjusted to the value prescribed in the
pH runs.   Thirdly, incubated blanks were used with each set of samples.
At the beginning of a run, a potato was selected and the specific gravity was
determined. The potato was sliced and subjected to a one-min blend in a Waring
blender followed by a 15-min grind at 30 rpm in a five-quart ball mill one- third
full with Burundum grinding media. The Burundum media were selected after the
unsuccessful use of stainless-steel grinding media. Also, a 15-min grind was selected as basic to all runs because of the highly variable results obtained by performing the tests with only a blended potato. The blended and ground potato was
diluted with distilled water to the point where it was of the right concentration to
be added to BOD sample bottles.
Four sample bottles and three incubated blanks were prepared for each day's
run -- accounting for 77 bottles. Four initial dissolved oxygen samples were
taken -- one each at the beginning and end of the test and two equally spaced in
the middle of the test. In addition, three glucose-glutamic acid standards were
prepared along with the five-day BOD samples to provide a check on the activity
ofthe "seed."
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