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Related Topic Tags
chemical oxygen demand (cod), industrial waste water, waste water (general), water (general), water analysis
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  #1  
Old 31st May 2012, 09:27 AM
nidhir's Avatar
nidhir nidhir is offline
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Please Help! Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

Dear all,
We currently use APHA method to determine COD in waste water. However, in the sample preservation method, there is a requirement to bring the ph < 2by acidification with sulphuric acid.
Our concern with this issue is that :
1. The industrial effluent may contain leachate which reacts with the acid and is dangerous for the sampler.
2. The effluent is at aroud 40 degress Celcius during sampling, hence adition of acid causes a very exothermic reaction, once again dangerous for the sampler and may be affecting other parameters to be tested.
Could someone help on these two issue.
Thanks

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  #2  
Old 3rd June 2012, 07:02 AM
Ajit Basrur's Avatar
Ajit Basrur Ajit Basrur is offline
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Look! Re: Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

Quote:
In Reply to Parent Post by nidhir View Post

Dear all,
We currently use APHA method to determine COD in waste water. However, in the sample preservation method, there is a requirement to bring the ph < 2by acidification with sulphuric acid.
Our concern with this issue is that :
1. The industrial effluent may contain leachate which reacts with the acid and is dangerous for the sampler.
2. The effluent is at aroud 40 degress Celcius during sampling, hence adition of acid causes a very exothermic reaction, once again dangerous for the sampler and may be affecting other parameters to be tested.
Could someone help on these two issue.
Thanks
Nidhir,

Question 1 - I am not sure.

Question 2, the samples have to be cooled to 4 deg C at time of sample collection.

Being a weekend, the response is slow. Let us wait for some experts to chip in early next week

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  #3  
Old 3rd June 2012, 11:13 AM
Dr. L. Ramakrishnan Dr. L. Ramakrishnan is online now
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Posts: 462
Re: Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

HI

I used to be a chemist once upon a time. My answers to your questions may be useful still.

1. If you suspect that acidification of the effluent may lead to emission of toxic substances (e.g. HCN), you can carry out the operation in a laboratory hood, wearing the right nose mask.

2. Addition of concentrated Sulphuric acid to water leads to generation of heat; a pH of 2 can be achieved by using dilute sulphuric acid (approx. 10 % sulphuric acid) without generating much heat. You don't need to add a large volume of the acid to water to get a pH of 2; a drop or two should be enough for say 50 ml of water (pH 7) to get a pH of 2.

Please do the sample preservation yourself and you will see that is not difficult.

With kind regards

Ramakrishnan
  #4  
Old 3rd June 2012, 01:31 PM
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Hershal Hershal is offline
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Posts: 2,363
Re: Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

Quote:
In Reply to Parent Post by nidhir View Post

Dear all,
We currently use APHA method to determine COD in waste water. However, in the sample preservation method, there is a requirement to bring the ph < 2by acidification with sulphuric acid.
Our concern with this issue is that :
1. The industrial effluent may contain leachate which reacts with the acid and is dangerous for the sampler.
2. The effluent is at aroud 40 degress Celcius during sampling, hence adition of acid causes a very exothermic reaction, once again dangerous for the sampler and may be affecting other parameters to be tested.
Could someone help on these two issue.
Thanks
Just a point of clarification, as I am not a chemist, others here are and will respond.

This is not for US EPA Water Sense?
  #5  
Old 3rd June 2012, 02:15 PM
samsung's Avatar
samsung samsung is offline
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Posts: 1,431
Re: Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

Nidhir,

You may refer this guide manual for water and waste water analysis.

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  #6  
Old 6th September 2012, 01:54 AM
huntpeter huntpeter is offline
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Posts: 4
Re: Chemical Oxygen Demand (COD) Determination in Industrial Waste Water

Quote:
In Reply to Parent Post by Dr. L. Ramakrishnan View Post

HI

I used to be a chemist once upon a time. My answers to your questions may be useful still.

1. If you suspect that acidification of the effluent may lead to emission of toxic substances (e.g. HCN), you can carry out the operation in a laboratory hood, wearing the right nose mask.

2. Addition of concentrated Sulphuric acid to water leads to generation of heat; a pH of 2 can be achieved by using dilute sulphuric acid (approx. 10 % sulphuric acid) without generating much heat. You don't need to add a large volume of the acid to water to get a pH of 2; a drop or two should be enough for say 50 ml of water (pH 7) to get a pH of 2.

Please do the sample preservation yourself and you will see that is not difficult.

With kind regards

Ramakrishnan
I agree with you.
Reply

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