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Borax as a Preservative of Dairy
Waste for the B.O.D. Test
LENORE JASEWICZ, NANDOR PORGES and  SAM R.  HOOVER
Eastern Regional Research Laboratory
Agricultural Research Administration
U. S. Department of Agriculture
Philadelphia
In pilot-plant investigations and industrial waste surveys, it is often
almost impossible to run B.O.D. tests immediately after sampling. The
validity of analyses of samples that must be held for several days or
shipped to a laboratory is open to question, especially when a soluble
material that is readily attacked by microorganisms makes up a major
portion of the oxygen-demanding substances. Previous studies at this
laboratory demonstrated that a dairy waste heavily inoculated with
aerobic microflora is rapidly oxidized if sufficient oxygen is available.
Thus a solution containing 1000 p.p.m. milk solids was about 40 percent oxidized in six hours, with an accompanying loss in B.O.D. of
more than 50 percent (2, 3).
Several possible methods of preserving B.O.D. have been studied
by other workers. Freezing the sample and holding it in the frozen
state is effective but often inconvenient. Use of a completely filled
sample container has been investigated by Horton (4), who found that
filled bottles of milk waste kept under water showed a negligible loss
in B.O.D. over several days. In studies requiring storage of casein
solutions at this laboratory, borax had been found effective at a concentration of two percent but completely ineffective at concentrations
below one percent. The work reported in this paper, which is of a
preliminary nature, was undertaken for the purpose of determining the
use of borax as a preservative for dairy wastes.
Borax, sodium tetraborate (Na2B4O7.10 H20), consists of colorless, odorless, transparent crystals that have a solubility of one gram
in 16 ml. water at room temperature and one gram in 0.6 ml. boiling
water. The resulting solution at room temperature is buffered at pH 9.2.
Borax is not oxidized under the conditions of the C.O.D. test.
Buchanan and Fulmer (1) in their discussion of effects of chemical
environment on the physiology and biochemistry of bacteria report
findings of other authors. Aspergillus was inhibited by one percent boric
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