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The BOD is a measure of biologically oxidisable material, resulting in dissolved oxygen (DO) depletion. BOD predominantly results from readily oxidisable, dissolved organic compounds.
A grab sample is incubated at 20°C over a 5-day
period. The sample BOD is the DO consumption expressed in mg/L.
The method takes five days to perform and uses a discrete sample. The test has poor reproducibility and toxic chemicals can inhibit measurement. Short-term BOD determinations magnify errors and still require relatively long sample periods. The test is not suited for on-line, continuous measurement.
Total Organic Carbon - TOC can
be used to report the dissolved organic compounds in less than 3
minutes. By determining the TOC or dissolved organic component of
a sample stream, a correlation may be set up with BOD that is typically
a 1:1 relationship, for samples containing low concentrations of
suspended solids. Peak organic loads may therefore be determined
in real-time.
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