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Effluent treatment -- problem with smell

Our factoryhas an ETP where canteen waste water, septic tank water and DM plant regenerated water is being treated. Its capacity is 200 T/Hr and max drain water flow is 100 KL/Hr. We are having problem of bad smell coming out of treated water. The temperature of inlet water is also at 40-45 deg generally (mostly due to canteen). Our ETP is FAB reactor type and is of reputed design installed only 5 yrs back. I need solutions to 4 problems in this regard

1. Why is the smell coming ?

2. Can I measure the smell coming and identify the root cause?

3. Is there any agency which can come to my site, study the problem in detail and help me solve it in India

4. If I can solve it myself, how to go about doing it?

Chetan G.K.




I need answers to several questions before I can give suggestions to solve the problem, and these are;

a) Is this the first time this ETP has had a problem of bad odour in the treated water since it was installed 5 years ago.

b) When the ETP was first installed, what were the effluents going into it?
Volume of each?

c) Clarify regarding the DM plant,is the capacity of the plant 200T/hr? The 'max drain flow of 100kl/hr' is it from the DM plant during regeneration?

d) When the ETP was first installed and started up,was there hot (40-45 deg.temp water) from the canteen coming into it?

I think the problem of bad odour could be due to any one or both of the following reasons:

1. A large volume of water from the DM plant comes into the ETP during regeneration.This is probably diluting the effluent substantially and thereby preventing microbial action necessary for an activated sludge process to function in the ETP.

2.The temperature of 40 to 45 deg from the canteen could also be affecting the microbial activity adversely .

The bad smell is due to improperly/inadequately treated waste water due to either reasons 1 or 2 above or both combined.

If you could send me your address of your factory, I will try and send an Environmental Engineer to look into the problem.


Consultant - Total Water Management



Segregation of the industrial effluents from the canteen waste / septic tank waters is the solution to the problem of bad smell faced by Chetan in his factory. The Effluent Treatment Plant (ETP) is meant to treat the industrial effluents, but not the domestic effluents. According to the Pollution Control Board, the domestic effluents should be discharged into the septic tank followed by subsurface dispersion trenches.

R. Jagadiswara Rao
Sri Venkateswara University
Tirupati, Andhra Pradesh

Dr. R. Jagadiswara Rao, Professor of Geology Retired, Sri Venkateswara University, Tirupati, AP 517502, India


Our thanks to Water Digest, for providing this answer -- India Water Portal Moderator
for providing this answer -- India Water Portal Moderator

• The smell is due to improper functioning of your ETP. If you are sure that previously the plant was working properly then kindly check the working of the Air blower installed for supply of air into the ETP. Otherwise provide me the water analysis report of treated and untreated water as described below and I can assure you that your problem will definitely be solved.
• Collect the water sample in a 2 liter plastic bottle and get the water analysis from any of the reputed water testing laboratory in your area like Sri Ram, Delhi test house, AES etc. The parameters for testing must include BOD, COD, TSS, Color, and Odor. The root cause can be found out only after getting the water sample.
• You can contact any water and waste water Treatment Company to visit your site and you will definitely get the complete solution including the supply of equipments and all. Otherwise you can also contact me for any kind of consultancy or information on my mail id
• Get the water analysis done as explained above and consult with any water treatment expert.

Aniruddh Gupta,
Water Digest Technical Expert & Sr. Engineer – PSE
Doosan Engineering & Services India Pvt. Ltd.;


Dear Chetan,

Please find my answers to your questions.

Why is the smell coming ?

The smell is coming due to the fact that bio-degradation is incomplete. Any plant or effluent smells because of putrification or anaerobic digestion of organic matter. Please identify whether the smell is generated from the start of the process or from the end part of the plant.

Can I measure the smell coming and identify the root cause?

Yes, if the smell is generated from the starting section of the plant, it is due to the anaerobic digestion of organic matter in effluent. This may be dues to oil and grease in effluent. Please collect the oil and grease from the trap as frequently as possible.

You may consider providing air from blower tapping into collection or equalization tank. This will result in incorporation of oxygen in incoming effluent and keep it reasonably fresh. If the smell still persists, try addition of liquid chlorine in the sump. The extra oxygen ion in hypochlorite shall carry out oxygenation and also disinfection by killing the bacteria that produce the smell.

Is there any agency which can come to my site, study the problem in detail and help me solve it in India.

Please call Akar Impex (P) Ltd., E-9, Sector 6, Noida. Their email id is: and

If I can solve it myself, how to go about doing it?

Please provide us with the layout and basic diagram with sizing of the units of the plant and we shall be able to tell you if it is a problem that can be tackled on your own or requires some specialised help from Akar.

Taral Kumar.
Akar Impex, New Delhi


Dear Chetan,

Many thanks for expressing your problems to us for some remedial procedures:

• What is the total flow per day and how much is the peak flow and how for much time.
• With the data given by you, we gather that smell is emanating i.e H2S and major non odour gases like methane is also there which is more trouble at campus due to local warming it produces by GHG-Green House Gas property of these gases.
• Is it possible to have the intrusion of bio-mass stopped or prevented by screen filtration at the outlet of kitchen waste-water/effluent.
• This bio-mass is taken on the route of bio-remediation by composting at site.
• When was the last time septic tank, and or soak-pit inspected cleaned...
• Manure generated can be co-mixed with gobar-cow dung and used in campus greens.
• We can come to your site and make the assessment and suggest simple remedies.
• Please fill up the water-sanitation questionnaire and send it back to us with complete plant and site particulars. Down load the questionnaire at click here.

With well wishes from Vigyanvijay,

Ajit Seshadri
Vigyan Vijay Foundation, New Delhi


The higher temperature(40-50deg) may cause lesser solubility of oxygen in the waste water. Is it the
reactor working under aerobic condition ? D.O. is to be monitored . If condition is anaerobic odour may be generated. But root cause can be found out.
Where is your factory? By inspecting suggestion for improvement could be given.
If you can understand the problem the you can solve the same.
Prof (Dr) Arunabha Majumder
AIIPH&H, Kolkatta


Bad Odour is possibly coming because your treatment may have turned anaerobic, due to lower oxygen levels.
Solutions can possibly be to increase your aeration capacity. You do not say how much of aeration you have. Best is to measure the level of Dissolved Oxygen and try to maintain it around 2 ppm.
Since you feed Septic Tank water here, which is basically an anaerobic treatment and would contain a huge amount of anaerobes, which have to mutate to aerobic state and maybe taking time. A possible solution would be for you install ATUs in your Septic Tank. Visit

Another solution would be not to depend upon intrinsic bacteria, which may not be functioning, as they should be. Try to go in for Bioaugmentation. For more details visit .

Keshav Agarwal
Technical Advisor
Biotech Services


Dear Mr.Chetan,

Often canteen waste is the culprit for such problems. Oil/Fat/Grease/(OFG), being long chain fatty acid is very difficult to degrade. These canteen waste when passes to the ETP it chokes up reactor and function of it is reduced over a period of time. Each waste has to be treated seperately at its source so that extra load is not transfered to the STP/ETP.

You need to have a Grease Trap(not mentioned in your query) and should be treated with Bio products for degradation of OFG.

Your query is very old but still if you have smell problem we can help with Bio products.

With regards
Hiren PAncholi

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