Chemical Oxygen Demand

Chemical oxygen demand (COD) is a measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. COD measurements are commonly made on samples of waste waters or of natural waters contaminated by domestic or industrial wastes. Chemical oxygen demand is measured as a standardized laboratory assay in which a closed water sample is incubated with a strong chemical oxidant under specific conditions of temperature and for a particular period of time. A commonly used oxidant in COD assays is potassium dichromate (K₂Cr₂O₇) which is used in combination with boiling sulfuric acid (H₂SO₄). Because this chemical oxidant is not specific to oxygen-consuming chemicals that are organic or inorganic, both of these sources of oxygen demand are measured in a COD assay.

Chemical oxygen demand is related to biochemical oxygen demand (BOD), another standard test for assaying the oxygen-demanding strength of waste waters. However, biochemicaloxygen demand only measures the amount of oxygen consumed by microbial oxidation and is most relevant to waters rich in organic matter. It is important to understand that COD and BOD do not necessarily measure the same types of oxygen consumption. For example, COD does not measure the oxygen-consuming potential associated with certain dissolved organic compounds such as acetate. However, acetate can be metabolized by microorganisms and would therefore be detected in an assay of BOD. In contrast, the oxygen-consuming potential of cellulose is not measured during a short-term BOD assay, but it is measured during a COD test.

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User Comments Add a comment…

about 1 month ago

dianarra zamora

what is the samling protocl in getting the COD???

3 months ago

Elhashmi M Abujaafar

Are There any Expriment ran on Lab-on-Chip

3 months ago

malvika

why one has to perform a COD or BOD or DO test

3 months ago

mandy » waiman0204 ((at)) hotmail dot com

may i know what is the reason that cause the measured COD reading is overange or underange? tahnks>

6 months ago

margaret » margsnoda ((at)) gmail dot com

Is there any other method to calculate the COD without using the formula.

8000(b-a)n/vol. sample

6 months ago

Sultan » sultan dot alrubkhi ((at)) orpc dot co dot om

Sir,

we use sulphuric acid to neutralize spend caustic but stil we found high COD.

Did you have any way to reduce the COD?

6 months ago

priya » manas_priya2002 ((at)) gmail dot com

Sir,recently we are doing a project by performing cod test on effluents coming out of some famous industries...could you please help us by cleary giving the details of the chemicals and reagents to carry out this test?

7 months ago

shafia leghari

Respected Sir can you tell how oxygen can be detected in laboratory by simple chemical test in organic compounds.

7 months ago

fred paras » utek102001 ((at)) yahoo dot com

Good day. We have analyzed our BOD and COD content on our effluent. How come our BOD passed the regulatory limit while the COD failed? How can I reduced COD on our effluent?

8 months ago

gs nagender » gsn ((at)) indochem dot in

dear sir, can you give some information , if cooling tower water contains COD 296 mg/lt and BOD 90 mg/lt. is there any corrosion problem [small pinholes in return water lines].what is the reason kindly mail me .gsn@indochem.in

8 months ago

M.fahim » fahim_ric01 ((at)) yahoo dot com

How can you differentiate between the COD and BOD?

11 months ago

priya » padu dot sweety ((at)) gmail dot com

Dear Sir/Madam, Good day! can you please tell me whether the COD value should increase or decrease when a microbe degrades waste inoculated along with it. please reply me.its urgent..

11 months ago

gugu zulu » gugu ((at)) tigerbrands dot com

I working for food company, we are having a problem with our COD and BOD, please help ,how can we solve it, but our effuent results, in term of pH and Tss are good.please help me urgently.

12 months ago

Zinnah » zoozim22 ((at)) yahoo dot com

Hi,
Thanks for such an excellent publication. After reading it, i realized that my doubts about the difference between COD and BOD were cleared.However, please include some quantitative analysis and laboratory procedures.

12 months ago

Ran Sarun » ran dot sarun ((at)) yahoo dot com

i want to know the effect of the Biological Oxygen Demand, Chemical Oxygen Demand and the Disolved Oxygen when it has high concentration.

about 1 year ago

manisha roy » manisha_roy85 ((at)) rediffmail dot com

Hello sir

I want to know that how calculate COD and BOD? pls help me.

about 1 year ago

chay » reachem_industries ((at)) yahoo dot com

Dear Sir,
Good day could you help me on what are the procedure on how to calculate hte COD and the reagents to be used.We have a product an acidic liquid soap and a basic liquid soap which we must test the COD.Thank you! God bless!

about 1 year ago

Andre » and_xool ((at)) yahoo dot co dot id

Good day sir...

Sir,i want to know how to reduce or decrease COD and BOD levels at industrial waste water or effluent...? In my company COD and BOD levels are very high, up to 1000 ppm. Please help me..

I'm waiting for your answer.! Thank's...

about 1 year ago

R.Jayapal » appliedco ((at)) vsnl dot net

Dear sir,

Please tell me How to calculate COD and BOD and Procedure.

over 1 year ago

bernard seneki » bernard_seneki ((at)) colpal dot com

I work for a processing industry. Please tell me ways I can reduce COD/BOD levels in industrial waste water.

over 1 year ago

philotsh » phitush2004 ((at)) yahoo dot com

thanks in advance. whats the relationship between COD and BOD- Is it possible to use biological means to reduce cod.

over 1 year ago

hetal mehta » hetal dot mehta23 ((at)) yahoo dot com

Hello sir, I want to measure H acid degradation by white rot fungi. I want to know is it possible to measure its degradation by COD? Can I determine its degradation using COD?

over 1 year ago

RENAN SADICON » sadicon_renan ((at)) yahoo dot com

Good Day, I would like to know why do we add minerals in dilution water like MnSo4, FeCl3. What are the effects of this compound to the dilution water? What is the purpose of Glutamic acid or GGA that we used in our standard? And most important the purpose of SEED in the analysis. I was just curious in the addition of dilution water that we used to fill up the BOD bottle to 300 ml. Thanks...

over 1 year ago

sangeeta dhote » sangeetadhote ((at)) yahoo dot com

Plz tell me in a lake eco-system for poluuting the lake how COD contributes?

I also want to know is there any relation ship between BOD and COD?

over 1 year ago

Shahaji Arun Mane » shahaji_mane7578 ((at)) yahoo dot co dot in

Rescepted sir,

Please sir tell me can we increase the COD of perticular organic material and how?

over 1 year ago

JOYDEB BOSE » j_bose27 ((at)) rediffmail dot com

Iwant to know that, is the process said above (cod test process)recognised by APHA?

over 1 year ago

N.celin manoj » celinmanoj24 ((at)) gmail dot com

Dear Sir, Plz tell me how to reduce the cod in paint effluent what vare the treatments and methods

almost 2 years ago

sagar » royaltyunlimited ((at)) gmail dot com

plz tell me the standard procedure 2 calculate the cod that means i want 2 know the materials required, reagents
requered,procedure, observation table, formula, precaution etc related with during cod measurement during lab

about 2 years ago

vipin » vipin dot bhagat ((at)) yahoomail dot com

Give the information how to calculate %oxygen consume.i mean formulas