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Reducing COD in final effluent wastewater
Q. We are currently experiencing high levels of COD in our wastewater stream. One of the methods I have researched in blowing air or oxygen into the effluent. I have carried this out on lab scale but there seems to be no effect on the COD content. Am I not performing the experiment correctly or is my method wrong? I am bubbling compressed air into a 25 liter drum of effluent and taking 20 ml samples every 1 hour these are then tested for COD. Do I need to stir the effluent before taking a sample? do I need to leave my aerated samples for a day or so before testing?
If anyone has any ideas or has performed this at lab scale and achieved good results please let me know.....
metals - Leeds, England, UK
A. It's not necessarily the case that the oxygen demand can be satisfied by making gaseous oxygen available to the liquid - the oxidisable constituents might not react with gaseous oxygen, but might need something like hydrogen peroxide or (dare I say it?) hex Cr or some other in-solution oxidiser.
Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
A. Blowing air or oxygen into a wastewater sample will not reduce the COD on its own. You need to add the air/oxygen and allow microbes to degrade the organic materials in the wastewater. This is typically done in a tank that provides retention of several hours to several days.
You may be able to get an almost instant reduction in COD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemical attack the organics in the wastewater, degrading them and reduction the measured COD.
Trevose, Pennsylvania, USA
A. Evidently, your waste water requires something stronger than atmospheric oxygen to address the COD problem. Sometimes, suspended solids are a big part of the problem and can be settled or filtered out. If not, you will need to use a stronger oxidizer, like bleach or peroxide, etc.Lyle Kirman
consultant - Cleveland, Ohio
A. The best way to reduce COD on wwtp is to have activated sludge on your treatment (propagation of bacterias in aeration tank, called biological treatment) using ammonium phosphate (fertilizer)can help propagate bacteria, a kilo of NH4OH a day for 100 cubic meter aeration tank.Teody Delgado
- Manila, Philippines
A. Try ultra-filtration; it is very effective on waste streams.John Neale
- Halesowen, West Midlands, UK
A. COD is a very broad parameter.
So the first step is to find out what substance is causing the high COD and only then to try a solution.
Two questions are crucial:
- which COD-rich substances are used in the plant ?
- taking samples of different rinsing waters and other waste water substreams : which are high in COD ?
Bubbling oxygen works fine if the cause is a large concentration of some inorganic reducing substance (e.g. Fe(II), sulphite, some of the reductors used in a chemical plating solution, ...)
Activated sludge (preferably the activated sludge of the local city waste water treatment station ; if not, your own installation which could be a serious investment) will do the job if biodegradable organic substances in solution are the main cause. Think of acetate and similar bath ingredients, most surfactants, ...
If most of the COD is coming from a water based degreasing operation, then try to separate the waste water from this operation and treat it physically (oil skimmer etc. or if you are using a degreaser with stable emulsions, ultrafiltration). (Find a lab to check the oil content of the sample with high COD).
Only if nothing else helps, switch to the very expensive aggressive chemicals like peroxide ... Even then, it is better to do this on the right substream which causes most of the COD load, before the final waste water treatment and not on the combined waste water stream.
- Gent, Belgium
March 13, 2008
Q. I have been engaged on a small organic food composting business. I have a problem COD level reduction in waste water from the composter. I had been tried to apply the aeration, peroxides, bleach and microfiltration. They helped a little. But it is not satisfying level. Now I am trying COD reduction from 16000 to 700 at effluent of the Composter. If anyone know how to reduce COD level down to 700 level, please let me know it.Kwansik Moon
Employee of the organic composter - Toronto, Ontario, Canada
May 2, 2011
Q. How to reduce COD load from effluent of dyes, only aeration or any other method -- kindly suggest to us?CHITRANG SAVALIA
Industrialist - ANKLESHWAR, India
A. Hi, Chitrang.
H2O2 and biological treatment were suggested as possibilities, plus Bert Gielen's explanation of when aeration alone might work and when it won't. He posted his recommendations of how to start choosing what to do... Please try to pose your question in terms of this discussion already on the table so we don't just run in circles :-)
Please tell us the wastewater volume, whether it is treated in batches or continuously, what COD you are starting at, and what COD you'd like to achieve. Thanks!
Ted Mooney, P.E. RET
Pine Beach, New Jersey
June 13, 2011
I am a chemical engineering student, currently doing my practical at a milk and cheese factory. We have a problem with the effluent waste water which is pumped to a farm and therefore the COD score must be below 400. At the moment it is at a average of 6000. I have read through the questions and responses on this page, but can't decide for myself which method to suggest to the management. The most economic method is also needed, since there isn't a lot of capital at hand. The tanks are continuous and I would guess the volume to be about 100 cubic meters. The surface contains a lot of fats and oils and therefore I am not sure if a simple filtration is going to do the job. Does someone have any advice?
milk industry - Ladismith, Western Cape, South Africa
A. Dear Friend,
As the fat & oil content is high, Initially you have to add HCl; and if you go for agitation followed by oil skimmer, you will get better result. After Oil Skimmer if you add Demulsifier , then you will get best result.
January 21, 2012
Q. In my vermi-filtration process, firstly COD decreased to 50 but after that, it is increasing ... why?
Please tell me the reason and solution.
- Chandigrah, Punjab, INDIA
A. Try using a Microbubble Aerator together with Microbes from Roebic. (You can google for websites). Economical and effective in degrading BOD & COD.Jay Lee
- L.A., California
February 28, 2012
Q. 1. WHICH SUBSTANCES CAUSE HIGH LEVELS OF COD IN BREWERY EFFLUENT AMOUNG THE FOLLOWING:
VOLATILE FATTY ACIDS
2. HOW CAN I SYNTHESISE A COMPOUND WITH HIGH COD AS A REPRESENTATION OF BREWERY EFFLUENT IN THE LAB?
student - Gweru, Zimbabwe
May 20, 2012
Q. I'm working in a dry laundry plant preparing detergent, we need to reduce the COD of waste water including sanitary and cafeteria waste water only. Can anyone suggest the best economical process to reduce it apart from using peroxides.Muhammad Farhan Qadri
- Karachi, Pakistan
August 10, 2012
Q. Dear Sir,
COD level in our fish processing plant is 5252 mg/l.
Please help us how to control and solutions.
foods - KAMPALA,Uganda
A. Hi Mr. Chandan,
COD for fish processing effluent can be effectively reduced by membrane bioreactor.
We have successfully used biological effluent treatment solution in Kenya and Uganda.
- Nairobi, Kenya
September 19, 2012
Q. Hi. My company is using Terephatalic Acid (TPA) and Ethylene Glycol (EG) as the raw material. Our product is Poly Ethylene Terephatalate (PET). This undergoes Esterification and Polymerization process. Waste product contains water and e.g., base. So usually C.O.D. reading is 10,000 mg/L. Please advise how to reduce as low as 8000 mg/L.Sunny Boy
November 2, 2012
Q. dear Sir,we have primary fruit processing plant(aseptic),juice production (jam & cordial), tomato sauce.
we had old ETP, but it is not working in to CEA requirement in our country.All process water (CIP-use quaternary ammonia as a antibacterial agent),kitchen waste,toilets & bathing water in to ETP.
Influent -BOD5=2510mg/l ,COD=3750mg/l,TSS=250mg/l
Qavg=7.2m3/hr , aeration tank capacity=323m3
we want to meet treated water quality as follows,
BOD5<30mg/l ,COD <250mg/l ,TSS <50mg/l
we faced PH reduction in aeration tank in several time & we partially sort out it increasing influent pH near 10 and try to keep pH near 6-7 range in aeration tank.But the final water quality meet BOD = 850 mg/l ,COD = 1013 mg/l yet. We also chemically treat after aeration.
We want to know cost effective way to reduce these values.
Please advise us to go ahead with this.
Your cooperation will be highly appreciated.
Thanks and best regards,
- Colombo, Sri Lanka
November 15, 2012
Q. I have conducted 6-month bio-treatment trial in a condominium septic tank. I was able to lower down the BOD, but the COD exceeds the 1:2 ratio. We must comply to BOD 50:COD 100 here. How come I can't lower down the COD with my bio-treatment?Gigi Montano
- Manila, Philippines
February 5, 2013
Q. Dear Sir,
My company produces pharmaceutical products. Our waste water treatment operates 100 m3/day continuously. Currently, we are facing bubble and high COD issues despite having biological treatment in plant. Do you have any idea how to solve both issues? I already checked our plant activities and found that no new chemicals or materials were introduced or used when the issue occurred. This totally gives me a dead end. Is there any solution that won't require me to use peroxide?
Pharmaceutical - Bandar Baru Bangi, Selangor, Malaysia
March 20, 2013
I'm currently employed in the petro-chemical industry. I'm working on ways to improve our current operation. We have, a bio-treatment facility utilising MBR technology, our COD levels are below the stipulated limits, however, I am looking at ways to improve the current levels as part of my final thesis.
- Cape Town, Western Cape, South Africa
August 22, 2013
Q. Dear sir,
We have a chemical plant and are having trouble to treat effluent water of high COD. Daily we have approx. 9000 liters.
Please let us help to reduce COD below 200 mg/l.
- Ahmedabad, Gujarat, India
August 29, 2013
A. Hello Mr Parthiv,
As Bert said above, "COD is a very broad parameter", please read his post, identify your flow source of COD, your main component that has high COD, and we might help you in choosing the best way to lower your COD value.
- Canuelas, Buenos Aires, Argentina
September 26, 2013
A. You can reduce COD by adding hydrogen peroxide.
June 6, 2014
Q. Dear All
We are a biotech plant with standard Effluent treatment plant (USABR followed by Aeration & clarifier then ACF filter). General sewage and caustic washing we are able to handle, and get the treated water COD less than 200 -- but there is a shock load (killed cell mass) of effluent from the manufacturing of 6.0 KL QTY once in 10 days which has COD around 30 million which is disturbing the entire stream.
Please let me know how I can instantly reduce COD in this biomass at least bring it down by 10 times so that my ETP should be able to handle it. I have read peroxide helps in instant reduction. Please confirm as I will take a trial of the same.
- bangalore, karnataka, india
September 12, 2014
Hypochlorite and anthracite only reduce COD to 110 ppm
Q. We are having high COD as 160 ppm, mainly cellulosic material.
We are dosing Hypo and reducing it to 130 ppm and with anthracite to 110 ppm.
This stream we are running in RO plant and further reduction of COD is needed.
Please suggest any dosing/pretreatment to reduce COD of this stream.
cellulosics - Kharach, Bharuch, Gujarat, India
COD is 9000 ppm and peroxide doesn't helpSeptember 14, 2014
Q. I've been experimenting with the use of H2O2 with one of my effluent samples and the result seems to go nowhere. Current reading of COD from the effluent is around 9000 mg/L. I've tried manipulating the H202's ratios and also pH of the effluent.
Is there any other solution to reduce the COD on site as I've been holding the effluent for about a week in a skidded tank?
- Johor, Malaysia
September 16, 2014
A. Hydrogen peroxide is a powerful oxidant, but unless it is used in conjunction with a catalyst, and/or UV light, it can be very slow to react.
Try adjusting the pH to 5 or so, and dosing with 200 - 500 mg/l of ferrous sulfate. Then add the peroxide. This is called Fentons reaction. It generates hydroxyl radicals, very powerful and rapid oxidizers. Other catalysts that have been used include vanadium pentoxide and copper sulfate.
Consultant - The Bronx, New York
September 22, 2014
Q. Sir we are experiencing COD levels around 150000-200000 ppm. Is there any method that can bring this COD levels to 10000-20000 ppm?k.vinay kumar reddy
October 7, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
We are designing a effluent treatment plant - 1000 GPD, to reduce COD from 150,000 ppm to 1000 ppmMohammed kaleem
process engineer - chennai city tamilnadu india
A. Hi K.Vinay. Surely there are such methods, but I doubt that anyone can offer practical advice without more info to go on. Sorry. Please give us some ideas on the volume, source of the waste, what other treatments (if any) have been done, etc.
Was that a question or an answer, Muhammed? If it's a question, 2 GPM is a small plant, but what industry is it serving (or is it sanitary waste), and what treatments have been done to it? Thanks.
Folks, please remember forum netiquette: it's your problem not theirs, so most readers consider it rude for you to ask them to spend more time on an answer than you spend on the question :-) Thanks and Regards,
Ted Mooney, P.E. RET
Pine Beach, New Jersey
October 9, 2014
Q. Dear sir,
This is a question, we need to reduce the COD to 1000 ppm; yes it for 1000 GPD small plant, but we need to have a treatment plant due to environmental restrictions.
- chennai tamilnadu india
November 14, 2014
Q. How can I reduce COD (chemical oxygen demand) in the waste water?
My waste water COD :- 9000 ppm and TDS :- 28000
December 22, 2014
Q. Dear friend,
I am vikram lad, working in Inorganic API industry. I want to reduce COD in wastewater. Generally our COD is about 1600 mg/l in water. Can you help me to reduce COD? Please suggest whether I should use hydrogen peroxide or FeSO4 or both.
- mahad maharashtra, india.
August 7, 2015
A. Yes, what Mr. Mooney so wisely said.
Without giving details about what process is generating the COD, it is impossible to say what the best solution is. If you have a waste with lots of carbohydrates, cellulosic materials, that sort of thing, chemical treatment is a loser - you would be better off with some kind of bio-reactor, let the bacteria do the work.
We are happy to help here but we're not mind readers, eh?
Consultant - The Bronx, New York
July 31, 2015
Q. 1. If using hydrogen peroxide is a solution for removing COD of waste water, then what is the daily requirement of the hydrogen peroxide, if we have to treat 450 KL water every day?
2. If using hydrogen peroxide is not economic for such large volumes then what are other options available. At present we are using a condensate polishing unit having Bio-Towers, Aeration & Clarifier Tanks, but COD is still 5500...???
ENA Distillation Plant - Karnal, Haryana, India
Ed. note -- Readers: This is a public forum with readers helping each other. This thread now has a number of unanswered questions! If you know enough about this subject to be able to post an answerable question, you probably know enough to at least try to answer one of the open questions :-)
Please try to answer one of the open questions, before posting your new question. Thanks!
May 12, 2016
Q. Dear All,
Our ETP (SBR with DAF) at a cow farm to treat cow dung has inlet & outlet parameters as below:-
Inlet after screening
pH - 7.38, TSS - 1242, COD - 3195, TDS - 3024
Outlet Parameter After Multimedia filters
pH - 7.3, TSS<5, Oil & grease<5, COD - 104, BOD - 20
We want to reduce the COD below 90. Can anybody help us with a viable solution, please!
Waste Water Treatment - Sharjah, UAE
May 13, 2016
We are manufacturing organic peroxide such as methyl ethyl ketone peroxide( MEK Peroxide or MEKP ). After reaction the waste aqueous layer has about 40,000 COD. It contains water, left over hydrogen peroxide, MEK, traces of MEK Peroxide. Need to reduce COD to 3000. MEKP itself is strong oxidising agent. Any treatment to reduce COD such as aeration or chemical treatment breaks the molecule and further increases the COD.
Any suggestions how to reduce COD !
- Mumbai India
Ed. note: This site is primarily about metal finishing rather than dairy farms and MEKP factories, but we'll post your question and see how it goes :-)
May 18, 2016
A. Fentons reaction, perhaps? Add H2O2 with some ferrous sulfate at around pH 5.
Consultant - The Bronx, New York