Special Tests for Industrial
Wastes
W. D. Hatfield
Superintendent of Sewage Treatment
Decatur, Illinois
There has been a rather high degree of cooperation between the
Sanitary District of Decatur, Illinois, and the industries in the city.
Such cooperation has proved very effective.
The problem at Decatur is largely caused by the organic food waste
from the corn-milling process. The corn-milling industry over the past
twenty years has been recirculating its former wastes within its process,
rather than adding fresh water, and finally evaporating the corn solubles to cattle food. This cattle food pays a profit, or at least the cost
of recovery, depending on the point of view.
In an industry of this size, grinding 50,000 bushels of corn a day
and using 20 million gallons of water a day, there are bound to be
occasional losses due to (1) entrainment from evaporators, (2) spillages
due to breakdowns, (3) careless operation in numerous departments and
(4) flour and syrup-car washings.
In order to reduce the losses to a minimum, the industry has a loss
department under the direction of a chemical engineer who watches the
processes and who studies the analyses and water balances. In 1924 this
industrial waste was equivalent to 10 population per bushel of corn
ground. At present, with careful control of the bottled-up process, the
losses are about one population equivalent per bushel of corn, or a 90%
recovery of their wastes of that date.
Now, where does the Sanitary District come into the picture ? Two
four-ounce samples of the sewages are taken hourly. One goes into a
composite bottle, and the other is stoppered. Both composite and hourly
samples are kept in a pop-bottle cooler at 4° C for preservation. Therefore, each morning the chemist has one average composite sample of all
24 hours, and 24 individual four-ounce samples representing each hour
of the day.
One of the first analyses made on the composite sample is the standard
permanganate oxygen-consumed test. Although this test is a purely
arbitrary test, it does indicate the relative amount of oxygen-consuming
material in the sample.   The result from this analysis, when multiplied
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