-- The Home Page of the Finishing Industry
HomeFAQsBooksHelpWantedsForum letter 7245
Serious Education ... plus the most fun you can have in metal finishing.

Reducing COD in Waste Water


Q. How can I reduce COD (chemical oxygen demand) in the waste water?

Sara Michaeli
chemical process supplier
Tel-Aviv, Israel


A. Sara,

I may be up a gum tree, as we say, but to increase the oxygen content of your waste water, have you ever tried to arrange a system such that nature will help?

In the fishery business a way they use is to discharge oxygen depleted water at a reasonably high level, 6 feet to 12 feet or so.

The discharge empties into a round plastic pipe or tube. There are a number of these identical tubes and each one is at least 9" above the next one. They are about 18" in diameter but could be larger.

Each tube has a perforated plate at the base to prevent 'packing', i.e. plastic mass transfer packing, from falling out ... although the Fisheries, being a little bit cheap, did use some fairly poorly designed packing.

The modus operandi is that this oxygen starved water falls down into and onto the packing where the flow is distributed and then dribbles out, reasonably evenly, from the perforated plate. Due to the 'fall' of the water, it automatically sucks in some ambient air = oxygen.

Ergo, ipso facto, you now have some somewhat oxygenated H20. OK? Let's hope it will work for you. If it does, please remit $ 10,000,000.00 so that I can afford to go on vacation! Good luck !

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).


A. Sara,

I found on the web this site:
[URL updated by editor Feb. 2014 because rearranged their site]

Maybe it can help you.

Good luck

Francesco Cicchetti
- Sulmona, Italy


A. Sara, Before I start looking for process technologies to solve various waste and pollution issues; I always like to take the process creating the waste back to ground zero and look at it from the point of view of what can be done to eliminate or change the various materials, process steps, equipment, etc. that is causing the waste or pollution in the first place and yet still maintain product specification. Or if that is not possible, change the product spec. such that, process changes can be made. I.E., "Change the process and material and spec., eliminate the waste". In order to do this effectively, this requires a little work and creativity.

If this is ineffectual or impossible, then end of pipe treatment technology is required. As for solving a high COD problem, this can be normally masked by oxygenating the waste stream by contacting the waste process stream with air or by the injection of oxygen. But remember, this is adding on additional equipment, materials, energy, etc. (hence increased maintenance and operations costs) There are plenty of vendors world wide that can supply this process technology. Check any of the waste water or chemical process websites.


Neil E. Hatfield
- Franklin Park, Illinois, USA


A. Sara,

Removing or reducing chemical oxygen demand can be done with a variety of ways including utilizing some chemical pretreatment, biological remediation or bioaugmentation in activated batch reactors wastewater pretreatment units. Depending on the upstream source that is contributing the high loads of COD in question and the daily volume loads needing treatment you may discover that you might be able to adjust the upstream contributing problems areas process control and reduce any problem areas. Small daily volume loadings ( less than 500 gallons ) may be cost effectively evaporated at $0.03-$0.10 per gallon. Pretreatment of high COD loadings is a bit of a challenge in the real world. Be cautious of any "Blue-Sky" remedies. COD loadings and the difficulties in treating them will vary as they are impacted by pH, various chloride loadings, temperature,presence of heavy metals,surfactants,F-M food to microbial loadings ratios, etc.

Fill in more info on your process, COD loadings, COD characteristics, goals, etc., to help paint a better picture of what you are facing.

Brian Lamphron
- Sioux Falls, South Dakota, USA


Advanced oxidation process

A. Sara,
You can reduce the COD using various methods. The best method I suggest to you if the COD of your effluent is more than 20000 mg/L.Then you should go for AOP (advanced oxidation processes). First bring the effluent pH to around 5-6 and treat with Fentons Reagent, wait for the flocs to settle.Then filter the supernatant using Activated Carbon filter. You will be surprised to see much reduction of COD after filtration.

Senthil D
- chennai,tamilnadu,India

August 29, 2010

Q. Dear Sir;
Can you help more in using Fenton's Reagent in wastewater treatment. I will appreciate your support.
Best Regards

Hashim Nasir
- Turkey

Fenton's reagent

Hi Hashim. Please see
and/or Wikipedia =>


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

March 20, 2012

Q. At SBR inlet, COD and BOD-3 values are 750 and 250 mg/l. Is it possible to achieve COD is <125 and BOD <15 after SBR treatment? Or do we need to provide sand filter and activated carbon filter after SBR? Effluent from Seepage Water Pump discharge, CRW and Effluent from Boiler Area under pressure to Equalization tanks and Oily water Sewer effluent (water seal drum of flare, floor wash, backwash effluent from ACF and diesel storage washing are main effluent for primary treatment.

Arindam Mukherjee
Oil and Gas - Vadodara, India

December 15, 2012

Q. Give me better solution for reducing COD in ETP [effluent treatment plant] or aeration.

Prajapati Damodar
student, no company - Ahmedabad, India

December , 2012

A. Hi cousin Prajapati. Better in what way than the five answers offered above, and for what specific situation?

If you can express your question in terms of the responses already posted, people will probably be able to help you and you should make progress. But your actual need might just be for a tutorial textbook on the subject.

Best of luck!


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

December 25, 2012

Q. Dear Sir/M'am,

My initial COD is 40000 mg/L but I want to reduce my COD up to 100 mg/L. What is feasible procedure?

Meeta Parmar
- Vadodara

December 26, 2012

Hi Meeta. It may be possible to chemically precipitate the contaminant to remove it, or to chemically oxidize it, or to biologically treat it in a trickling filter or activated sludge. But what type of waste? Why do you object to the ideas previously offered? How many mL is in the beaker of waste that you need to treat, or how many millions of gallons per day must you treat?

I can't personally answer your question, but readers of this site honestly want to help you. But when a posted question is so vague that it can't be answered except prefaced with many pages of ifs, ands, and buts, it almost simply will remain unanswered. Sorry! Please try to understand that people need a good description of your situation, not a single sentence, to personalize a solution for you.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

May 8, 2013

Q. Hi. Please, I need suggestions to reduce the COD level to less than 750 mg/l. I am working in printing industry and the COD level is 1800 mg/l; and the fat, oil, grease is 10 mg/l. Need to lower it to less then 5. The authorities are asking me to use a treatment unit. I need something reasonable.

shareea marafie
- kuwait sabhan, kuwait

June 29, 2013

Q. Hello friends,
I want to treat waste water from coal base gasifier. Please suggest me treatment to reduce COD from 8000 to 250?

dwijen vyas
thermal power plant - Ahmedabad,Gujarat,INDIA

August 3, 2013



February 24, 2014

Q. Dear Sir/Madam,
I need to know about a suitable treatment method to reduce COD level from 5000 mg/l to below 1000 mg/l.
So please give me your comments for this.

Sureni Nisansala
- Sri Lanka

February 26, 2014

A. Hello,
You don't mention what type of industry you are involved in. Is your system closed looped? Anyway, have you considered using activated carbon? There are in-line carbon filters that could be installed to reduce organics. If the organics are reduced, the natural reaction of organics/oxygen will also be reduced.

Mark Baker
Process Engineer - Malone, New York USA

March 3, 2014

Q. Dear Sir/Madam,
I want to treat high amount of soap and about 5000 mg/l COD load effluent. It is a continuous process. So please give me a suitable method to reduce this COD load up to 1000 mg/l.


Sureni Nisansala [returning]
- Sri Lanka

March 20, 2014

Q. My company operates a distillation column to reclaim solvents to be reused in the manufacturing process. The bottoms coming off of the column are viscous and have a high COD value. What are two hazardous waste treatment processes that you would recommend to use to treat this hazardous waste?

Sid Watson
- New Jersey, New Jersey USA

October 18, 2014

Q. Sir;

We are manufacturing caramel and synthetic food colours. Our waste water is coloured and BOD value is 300, and COD is 2000. How can I reduce my BOD & COD to less than 30 & less than 250, respectively?

seetharaman sureender
- pondicherry, India

Excess BOD & COD during heavy rains

November 17, 2014

Q. I have a problem with BOD and COD in final discharge. For your info my company are doing transfer station for domestic waste. As you know, waste in Malaysia mostly are wet and this will produce more leachate/wastewater. Actually we already do the collection point for leachate/wastewater direct to Wastewater Treatment Plant. But when heavy rain, the wastewater will be overflow and enter the pond which is our final discharge. When this happens the BOD & COD will exceed the limit. So do you have any idea for us to solve this problem. Thanks for your kind attention.

mastura sam
- shah alam, selangor,malaysia

November 2014

A. Hi. I don't know the answer, but you might read up on New York City's sewerage treatment approach. NYC was built before the days of separated sanitary sewers and storm sewers, so they have the same problem when storm waters run into their system.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

How to predict/calculate COD based on sugar contents?


December 1, 2014

Q. For example, I have 15 brix, one lit. of beverage, and it is to be added in 5 KL of water. Then what is COD level?

Itikyala manjunath
- Hyderabad, Telangana, India

May 5, 2015

Q. Question - The waste water treatment plant constructed for a Printing Company reduced COD level to 900 from 2000 mg/l through PAC Floculation and sand filtration. But our Target is to reduce COD Level to < 250 mg/l. What should be the pH of the Waste water suitable for PAC treatment?

Karuna Susil Senaviratne
Environmental Laboratory - Colombo 10, Sri Lanka

June 2, 2015

Q. My COD:BOD ratio must exceed 6:1 or incur a surcharge from my local water district. My water sample is lower, around 4:1. The content of my water is a post plastic separation using specific gravity (water, surfactant and table salt or just water with a surfactant). I generate ~300 gallons/day of solution with plastic fines. I can filter out the plastic fines in a gravity feed system I have put together. I have read that aeration is inexpensive way to increase the oxygen content. Is this the simpliest solution? I am in no rush to finish the water.

John Kelly
- Gloucester, Virginia, USA

June 9, 2015

A. Aeration is a good way to go. I believe you could also use a swimming pool floating chlorinator with a couple of chlorine tablets added daily. Make sure to check with your POTW before using the chlorine.

Dan Mack
- Horicon, Wisconsin

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 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
Teds signature
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 wich 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.


ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2017     -    Privacy Policy
How Google uses data when you visit this site.