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topic 7245, p3

Reducing COD in Waste Water

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A discussion started in 2001 but continuing through 2019

May 31, 2017

Q. Hi
I have to treat a effluent of BOD - 16700 ppm and COD - 45000 ppm. Oil (Free oil) - 875 ppm and emulsified oil -3750 ppm.

The feed is industrial effluent from 4 different sources. The treated effluent characteristic requirement is BOD < 20, COD < 200, Oil <5

Can you suggest best suitable scheme for the same.

I was thinking of giving following scheme

Feed -> Equalisation tank-TPI-DAF-1 - DAF2 - Aeration 1 - Clarifier 1 - Aeration 2 - Clarifier 2 - MGF - Treated water

Please comment.


Cost effective ways to remove phenol from waste water?

July 29, 2017

Q. I work in a petroleum refinery. We have high phenol in our sour water.
Kindly introduce me to cost effective ways of removing this. My target after removal is 0.02 ppm.

Victor Lebi
Engineer - Port Harcourt Nigeria

September 24, 2017

Q. Hello,
I need to help to reduce the COD less than 3000 mg/l.
My effluent water content mostly sulfide and thiosulphate and also be other with basic pH up to 11-12. My initial COD level of waste effluent water is 70000 mg/l. First of all I set pH of this water up to 6. Lot of thiosulphate and other salt precipitated out which I removed through filter. H2S gas evolved out.
I checked the COD, which is 23000 mg/l. Then I take PH up to acidic 3.
Then I use fenton's reagent treatment. I coagulate this with PAC and filter it. I check the COD which is 15000 mg/l.
Now I can't reduced it up to 3000 mg/l.
I also used carbon bed filter, but can't reduce it.
So, please help me.

Kaushik Ramolia
NIC Bioscience Pvt Ltd - Ankleshwar, Gujarat (India)

December 17, 2017

Q. Hi, my cake factory generates 7-10 Metric tons/day of effluent waste water. The latest BOD/COD analysis was 1530/5520 mg/L, which is above the regulatory requirements. My pH is also low 5.1, and oil&grease is 273 mg/L. The sample was taken just before the grease trap. Some company suggested to dose H2O2. Please advise if it is suitable to reduce all values by 50%? I need the method and dosage and concentration. Please give me details.


Hassan Itani
- Dubai, UAE

December 21, 2017

A. Hi Hassan,

You say the sample you measured was taken just before the grease trap, so I would advise to take another one after it to see if it lowers that value somehow.

For BOD and COD, chlorine is always my first choice if applicable, there are many other choices but every one is more expensive than the first one. Controlled chlorination may be helpful lowering those values down to your requirement.

You may have to adjust pH to the best precipitation value if you have any metals in solution. If not, don't and just adjust if the chlorination performance needs it.

AFTER you have treated all oils and organics, sedimented and filtrated your wastewater, adjust pH to your requirement.

You could make all these steps in lab and try to extrapolate what could occur in your plant.

I hope this can help you! Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

December 26, 2017

Q. Dear readers,
I'm currently at a manufacturing site for springs that uses oil and machine tools.My COD is at 15000 mg/l after cleaning these springs.I am using solvents such as isopropyl alcohol and sodium hydroxide for their cleaning and processing but that yeilds a very high COD. I would like to reduce this COD to as minimum as possible as per the requirements.

If you would have any recommendations it would help me out a lot.

Thank you very much!.

Waseem Iftikhar
- Budapest, Hungary

March 20, 2018

Q. Hi, I want to treat effluent of paper industry which has BOD -100 ppm COD - 200 ppm TSS 200 ppm. The effluent is ETP treated effluent where high BOD COD is reduced up to above-provided level, Now I want to further treat through membrane separation, Please advice what should be best pre- treatment technology to feed can such parameters in UF RO system. The existing ETP have aeration and filtration technology, so I am not preferring the similar technology to further treat same effluent.

Amit Goswami
Pennar Enviro Limited - Hyderabad, Telangana, India

May 25, 2018

Q. Is there any possibilities to remove COD from wastewater using inorganic minerals rather than using chemicals? If so, how?

Logesh A. Raja
- Bhuj, Gujarat, India

June 2018

A. Hi Logesh. There is perhaps a language issue here because inorganic minerals are probably chemicals. But you probably mean some mineral or material that you can dig up from the earth and add to your wastewater without any further processing, like sand or mud or peat or coal?

My very limited understanding is that the bacteria in activated sludge can reduce COD depending on exactly what is the source of the COD because some portion may be biologically reducable, and some portion may not. I would say that, in theory, adding a bacteria-rich inorganic material could constitute an activated sludge process … although obviously a carefully researched & designed process is more likely to be successful than a haphazard one.

Please give us the details of your situation.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

September 26, 2018

Q. In a electroplating process industry, COD 1700 ppm, CN 3 ppm. How to reduce them?
How to control process to reduce COD/Ni/CN ? Specially in rinsing of metal finishing effluent we get these wastes.

Noor sabah
Electro plating metal finishing - Karachi, Sindh, Pakistan

September 2018

A. Hi Noor. You should try to minimize your waste by returning rinsewater to the process tank when possible, then keep the cyanide separate from the nickel because treatment gets very difficult once combined. Then you oxidize the cyanide, precipitate the nickel, and settle or filter out the solids.

Digital version

(No longer published, but Elsevier hasn't yet de-commissioned the online version of the Guidebook)
Download it before it disappears.

You can start with the Metal Finishing Guidebook which has chapters on wastewater treatment, minimization of waste, and similar topics =>

You can also search the site for topics like "Cyanide Treatment" and "Nickel Waste" -- you'll find dozens of threads on those subjects.

It's not that I don't want to try to answer your question more fully, but it covers whole shelves in technical libraries, with books like:
Kushner's "Water and Waste Control for the Plating Shop" [link is to info about book at Amazon],
Cherry's "Plating Waste Treatment" [link is to info about book at Amazon],
Clarence Roy's "Operation and Maintenance of Surface Finishing Wastewater Treatment Systems" [link is to book info at Amazon]
and many others devoted to it. We can probably answer very carefully delimited questions, but for highly generalized ones we can only refer you to references. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

October 4, 2018

A. Hello, Noor:

It's worth a try to add some hydrogen peroxide to the wastewater prior to settling or whatever method you use to reduce solids. I can't say how much, since you provide no numbers, but a few percent of the 35% grade might be more than enough.

Hydrogen peroxide is not terribly expensive in industrial quantities, and, possibly, might solve all your problems simultaneously.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

January 16, 2019

Q. I am Working on a Phenalakamine wastewater. It's COD is around 100000. By performing Fenton's I am able to reduce it till 30000. How to remove more? Please suggest.

- Mangalore, Karnataka, India

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