Chemical Oxygen Demand ( COD ) : FWQ

Waste Water Quality ( FWQ )

COD ( waste water quality parameter )

COD : chemical oxygen demand

➙ COD ( chemical oxygen demand ) indicate how much organic pollutants is present.

• BOD
• COD

Used for organic pollutants strength

Definition COD :

➙ Chemical oxygen demand is the test to determine the amount of oxygen required to oxidized organic matter in acid condition into carbon dioxide ( CO2) and water ( H2O ) using strong oxidizing agent.

Limitation of Chemical Oxygen Demand Test

➙ No clarification of biodegradable and non biodegradable organic compounds present in sample.

COD = BOD + Non Biodegradable
COD - BOD = Non Biodegradable

➙ All The Organic Matters Does Not Oxidize With Weight Chemicals Method.

Example: aromatic hydrocarbons ( phenol )

➙ When the best water have presence of inorganic compound like, chlorine, sulfate etc. Then auto is consume by this organic compounds and COD results will be errornevs.

➙it does not provide any information about the rate at which organic compounds are being stabilize/oxidise.

Advantage of chemical oxygen demand ( COD )

➙Short analysis time compared to BOD Test.

BOD Test	3 or 5 day's
COD Test	3 hours

➙ Sometime COD test can be perform when COD and BOD ratio are Established.

History of COD Test

➙By oxidizing agent = K2 Cr2 O7 ( Potasium Dichromate )

➙KMno4 ( potassium permanent )

➙K2Cr2O7 :- Available in High scale of purity ( 99.9% purity).

➙K2Cr2O7 is a primary solution and price is cheap as compare KMno4.

➙K2Cr2O7 more strong oxidizing agent.

Limitation :

Low molecular Fatty acid
Pyridine - non biodegradable
Aromatic hydrocarbons

➙Compound | chemical used to remove interface

Note :

➙Theoretical Oxygen Demand is High > COD > BOD