What is the relationship between BOD and COD?

Document ID

Document ID TE174

Published Date

Published Date 27/05/2017
Question
What is the relationship between BOD and COD?
Summary
Comparing BOD and COD results
Answer
BOD can be estimated from COD measurements, however the ratio of BOD to COD can only be found by measuring BOD and COD over time and using this data to find a correlation.

-Once you have gathered COD and BOD data for your sample, divide your average BOD result by the average COD result to find the ratio or conversion factor.
-Multiply your COD results by this factor to estimate your BOD concentration.

*COD values are almost always higher than BOD results for the same sample; the conversion factor should be less than one.

This correlation will only apply to the sample that you compared. If your sample composition changes significantly, for example seasonally, a new ratio will need to be determined.