Total Organic Carbon in Water
The Total Organic Carbon (TOC) content is another measure of the organic matter present in water.
It seems likely a more comprehensive indication of organic pollution loads can be obtained in this way than any other. In this test, all the carbon in a sample is converted to carbon dioxide and then is measured by infra-red spectrscopy.
Useful information for deciding the nature of the water can be obtained by dividing the COD by both the BOD and the TOC value. In general, COD divided by BOD will be in the range of 1.5 to 3 for substances in water that are readily biodegradable, and from 4 up to as high as 12 to 15 for toxic or nonbiodegradable substances.
The COD/TOC data would be useful in determining whether the COD of a water was due to organic or inorganic reducing agents. If inorganic reducing agents were present, the COD/TOC ratio would be extremely high.