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topic 7245, p2

Reducing COD in Waste Water

1       2

A discussion started in 2001 but continuing through 2018

September 1, 2015

Q. Hi, I'm working in an ice cream producing company, we are currently experiencing a problem with a high COD of about 4000 mg/L and we want to reduce it to anything less than 1000 mg/L. What are the right processes to use in order to resolve this? We currently using DAF process to treat the effluent from the factory. Thanks a lot in advance.

Jeseriel Moabelo
- Johannesburg, South Africa

Reducing BOD in Sewage Effluent

January 11, 2016

Q. I am an Environmental Scientist and offers Consultancy service to company. A client of mine has a sewage treatment plant from which we collect their effluent to determine its BOD and Coliform level for regulatory purpose. However, the BOD value we get ranges from 100 to 250 mg/l, while the regulatory limit is 45 mg/l. What can be done to reduce the BOD value.
Is it possible for the Fecal Coliform Count to be as low as 10MPN/100ml while the BOD is as high as 250 mg/l?


Taofeeq Adeosun
Environmental Consultant - Ikeja, Lagos, Nigeria

January 11, 2016

A. Chlorination is a bad idea, IMHO. It might help you pass but It'd be by "fooling" the test.

You might try adding some hydrogen peroxide and aerating. Seeding with some microorganisms wouldn't hurt.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

February 29, 2016

Q. Hello Sir,
My effluent initial COD is approx. 2500-3000 & pH is 6-7. I want to reduce that COD with "Fenton's reagent". Which dose gives best performance?
Please send me your feedback quickly.

Hardik Bhalala
- anand, gujarat, India

February 2016

A. Hi Hardik. You may consider my response to be "ducking the question", but please listen anyway because so many people get themselves into rapidly escalating trouble by making the same huge mistake --

You NEVER determine wastewater treatment regimens or reagent usage by theory; you always do beaker tests and, after you have proven a successful treatment regimen, you scale up proportionately from there. Good luck.


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

June 29, 2016

! How about using the COD as an advantage. The more COD, it is more advantage.

keshava puri
- nagpur, maharastra india

June 2016

thumbs up signHi Keshava. I'm all for that, but how do you propose to use COD to advantage?


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

June 29, 2016

A. The so called wastes, mainly liquid wastes, are used in agriculture irrespective of bod, cod, pH, etc. ... and good, high quality organic food is produced. We have been doing it since long.

keshava puri [returning]
- nagpur, maharastra, india

July 2016

thumbs up signHi keshava. You may have been doing it for a long time in India, but I don't think it's ever going to happen in the USA.

We are very queasy about the idea of using wastewater for agricultural irrigation -- but not the least bit queasy about importing uninspected food from places where they do so :-)


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

July 5, 2016

Q. Hi, I am currently handling a waste water treatment plant for a poultry factory in Malaysia. I would like to know more how to reduce COD at the same time maintaining the pH of treated water by adjusting the nitrification (blowers) and denitrification time. The pH of the water tends to be acidic at the moment. Thank you.

Daph Ling
Poultry Factory - sarawak, malaysia

July 2016

thumbs up signHi Daph. We're pleased to post your inquiry but must remind you that this site focuses on metal finishing. So, few of our readers probably have much experience with poultry wastewater, nitrification, or de-nitrification.


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

August 8, 2016

Q. Hello friends,

The COD of the decanted water is <100 ppm. How to reduce it to near zero level for reusing it as 'make-up' water or for flushing? Also, the water is turbid with around 200 NTU. Kindly suggest techniques for the same.

Ganesh Vedhachalam
PVC resins - Rajasthan, India

August 17, 2016

You might be able to remove the turbidity by applying a suitable flocculant (polymer).

I'd suggest you also pose your question in one of the wastewater groups on LinkedIn. You might have better luck there.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

September 5, 2016

Q. Good day, we are operating a leachate treatment facility for our Sanitary Landfill Facility using STM Aerotor. We have problems on the COD content of our effluent which is very high. After process the decrease in cod level in quite not that good, still not attaining water quality standards for safe discharge. Can you give us effective ways of minimizing cod level of effluent? Thanks.

Solid Waste Management - Olongapo City, Philippines

thumbs up signHi Loreli. I hope someone helps you, but you can see that there are several unanswered questions on the thread before yours :-)

This is not a consulting service, but a free public forum where people must help each other if help is to be gotten. While you are waiting for help, please see if you can help answer one of the open questions preceding yours. Thanks!


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

January 15, 2017

Q. Hello friends,
I would like to ask what should be done in the case of chemical effluent such as strong and weak acids, surfactants, solvents with avg COD value 6000 mg/l, what method should I use to reduce it? Please kindly reply.

Sandip Patil
- Mumbai,INDIA

January 2017

A. Hi Sandip. You never combine wastes except:

- After you have determined that there is no practical way to recycle the individual contaminants back to their original process, and
- After you have developed a treatment regimen where you know that they will not interfere with each other excessively.

If this is a plan for ongoing treatment, you must change it and separate those wastes -- for example, solvents & surfactants can make acid/alkali neutralization and precipitation of metals nearly impossible. If this is a one-time mess, such as a floor spill after a fire, you could try to carefully characterize the waste for us and see if you get any good hints, but you may need to ship the tank truck (or whatever) of waste to a competent facility. Good luck.


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

January 16, 2017

A. You need to specify the volume per day to be treated, and also whether or not the analysis is on a filtered or an unfiltered sample before any advice can be given.

Lyle Kirman
consultant - Cleveland, Ohio

January 30, 2017

Q. Hello friends,
This is our wash water and we can't recycle it; so what can do in same case? Kindly suggest specific method, procedure to handle it.

Sandip Patil [returning]
- Mumbai,India

January 2017

A. Hi again. So you are saying that this is one bad batch of wash-water waste you must get rid of? You should probably send this to a treatment facility which is able to thoroughly analyze and treat it . . . and make sure you separate your processes in the future so you don't generate any more. It should be very practical to keep the solvents away from the strong acids, for example.

Unfortunately, you could read a 400-page book and still not know what to do with it, but you must start with a pretty good analysis of what it is, as Lyle notes. Sadly, uncategorized mixed wastes with solvents, COD, strong acids, surfactants, etc., may contain powerful organic acids, and might possibly even be explosive -- they are not ideal for trial-and-error learning. Again, you must keep the solvents away from the acids.


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

January 31, 2017

Q. Hi and thanks for suggestion, I'm trying to get rid of it. Further will try to minimize generation of wash water and will take care about solvents which has explosion hazard. Please reply if any ...

Sandip Patil [returning]
- Mumbai ,India

thumbs up sign Hi Sandip. If there is a lot of water in this batch, it's very unlikely to be explosive ... sorry, I'm not trying to frighten you. But I am suggesting that you can't allow various types of waste, like strong acids & solvents, to mix together randomly and then later properly treat it for disposal inexpensively, and without analysis & instrumentation.

In any case, if you must treat this batch in-house, the way you do it is by experimenting on one beaker of the mixed solution, keeping careful notes about what you do. When you have developed a successful protocol, you repeat it several more times with a beaker to be sure before you scale up to mixing any further chemicals into the whole batch. Good luck.


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

April 18, 2017

Q. Hi Sir,

In my process by-product heptahydrate sodium acetate is found in dissolved form in water and gets Higher COD value after chlorination so, how to reduce COD?

Sagar patel

May 22, 2017

Q. Hello,

I work in a fiberglass finishing facility. We have numerous chemicals that end up being used as finishes, but the primary chemicals are silane and chrome based.

Before the year 2012, our COD levels were around 100-800. In recent years, we've seen miscellaneous spikes that put us above our city's operational ordinance - resulting in fines.

Following high test results, we would clean our site pit, and the levels would come down following testing. We tested in April and our levels were around 2204. This was following a thorough clean of our pit, but the levels remained high.

Do you have any thoughts on what could be contributing to our high COD levels, and what would be causing them to spike and then stabilize during recent testing?

Sean Syring
- Seguin, Texas

May 26, 2017

A. Hi Sean,

I would think chrome based chemicals shouldn't make the COD go up, and I don't know about silane-based chemicals as I haven't worked with them and don't know how you treat your wastewater.

Please, specify how you treat your wastewater, and if you know which chemicals are present in your final effluent water. If not, I would search for:

- Reducing agents
- Solvents
- Hydrocarbons (oils, greases?)
- Chelating/wetting agents

I can't say what is the problem without further data, and I can't assure we can solve this, but I think that while you are searching for data, you will learn something more about your process.

Regards and best of lucks!

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

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

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