[asqa]

is there any relation between TOC/COD/BOD, if so give details.

[DrCMS]

They are all related to the amount of material in a sample but there is not a formula you can you to get one from another.

COD is the chemical oxygen demand and is generally the highest figure as it covers all the organic and inorganic material that can be oxidised in the sample

TOC is the total organic carbon only

BOD is generally the 5 day test and will be less than the COD.  How much less depends on whats in the sample.

If all the material is biodegradable the BOD will still be less than the COD as it quite often takes up to 20 days for all the the material to get oxidised.  
However as i told you in your BOD thread 5 days is the standard test for historical reasons.
If some of the material is not biodegradable the BOD will be a lot smaller than the COD.

[asqa]

thanks Dr. CMS