Frequently, BOD is measured in a sample after a specified
incubation period, typically 5 days. The resultant BOD value, while
informative, does not provide any kinetics information that can be
used to estimate how the BOD will be expressed in the receiving water
or for modeling purposes (Ward, 1999). Long-term BOD series no
longer are performed commonly, and only one study was found in the
recent aquaculture literature that quantified UBOD and characterized
BOD fractions in channel catfish pond waters (Boyd and Gross, 1999).
Sometimes, for samples high in labile carbon compounds (such as
sewage effluent), after the DO depletion appears to have nearly converged
to its asymptotic value, a “second stage” reaction begins, typically 5–
8 days after initiation of the incubation, in which the rate of oxygen
depletion accelerates then tends asymptotically to a higher value. This
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