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Afshin

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Mixing of two different COD wastewater
Apr 28^th, 2012, 1:03am

Dear Expert Members,

I want to mix two different COD wastewater in Equlaization Tank, my first question is, is it importnat low strength waste water pour in tank before adding high strenght waster water? Second if answer is positive, how much low strength waste water level should be in Tank before adding high strenght waste water?

Thank you in advance.

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Jeff Naumann

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Re: Mixing of two different COD wastewater
Reply #1 - Apr 28^th, 2012, 9:29am

What are the actual COD concentrations, and volumes of each waste?

Why do you want to mix them? As long as there are no chemical incompatibilities between the two wastes, it doesn't make any difference which way you mix them. If one is a strong acid and the other neutral or alkaline, you would want to SLOWLY add the acid to the other liquid, while mixing.

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grrun God Member Offline WaterandWastewa ter.Com is the best! Posts: 3525 Pekin, IL Gender: Company or Organization: Freelance Environmental Engine	Re: Mixing of two different COD wastewater Reply #2 - Apr 28^th, 2012, 2:17pm Are the discharges continuous? Once the equalization tank is filled; the COD output should vary less because of the equalization tank. Anyway, more information about what you are trying to accomplish with the equalization tank is needed. grrun
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Re: Mixing of two different COD wastewater
Reply #3 - Apr 28^th, 2012, 10:33pm

Hi,

Thank you for your replies. High Strength COD range is between 10,000 to 20,000 mg/lit and flowrate between 0.5-1 m3/hr and low strength COD rang between 500 - 1000 mg/lit with flowrate of 10-20 m3/hr.
Equalization Tank volume is net 500 m3 capacity.

The objective of mixing is to reduce High Strength COD lower than 1000 mg/lit so can be treat in existing effluent treatment system.

Any quesstion let me know.

Thankss

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grrun

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Re: Mixing of two different COD wastewater
Reply #4 - Apr 29^th, 2012, 1:46pm

Based on the average COD concentration; the resulting mixture would be over 1,000 mg/L more than 50% of the time:

((0.5 m³/min)(15,000 mg/L)+(15 m³/min)(750 mg/L))/(15.5 m³/min) = 1,210 mg/L

Unless there is some sort of control over the two waste streams, I would predict that you couldn't accomplish your objective (based on the data you've provided).

grrun

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Afshin YaBB Newbies Offline I love Water and Wastewater.com Posts: 8 Company or Organization: MMC	Re: Mixing of two different COD wastewater Reply #5 - Apr 29^th, 2012, 6:42pm Grunn, There is a flow controller in High Srength Flowrate enable operator to set high strength waste water flowrate. Sometimes flowaret for this stream should be below 0.5 m3/hr. Afshin
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Jeff Naumann

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Re: Mixing of two different COD wastewater
Reply #6 - Apr 29^th, 2012, 8:52pm

As George (grrun) has shown, you are not likely to achieve your target, unless the total volume of "high-strength" waste is low enough so that you could store that and bleed it in with the "low-strength" flow to meet the COD criteria. In other words, if say the high-strength flow is produced over only six hours per day, while the "low-strength" waste is produced over say twelve hours per day, you might achieve your goal.

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shissun YaBB Newbies Offline I love Water and Wastewater.com Posts: 1 Gender: Company or Organization: Nabbir Laboratory	Re: Mixing of two different COD wastewater Reply #7 - Apr 29^th, 2012, 9:52pm Jeff, good idea. It may need another tank to reduce the flow of high-strength stream to achieve <1000mg/L COD. Btw, what kind of organics in this wastewater, please?
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Tom Keenan - nesa

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Re: Mixing of two different COD wastewater
Reply #8 - Apr 30^th, 2012, 11:43am

If there is a continuous flow of both streams, you will only achieve the 1,000 mg/l COD at times when the high strength stream is at its lowest and the low strength flow is at its highest.
Really there is not enough information to allow a decision on how often the desired limit of 1,000mg/l can, or will be achieved.
If you know the daily or weekly inputs from both streams, you can use these to calculate whether or not the "limit" can be achieved in the equalisation tank over time.
Can you provide any more information?

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Re: Mixing of two different COD wastewater
Reply #9 - Apr 30^th, 2012, 8:00pm

Dear All,

Thank you for all of your replies. Actually High Strenght W.W. produced during plant maintenance mostly because of flushing of equipments by water, the expected H.S.W.W is about 900 m3 per each plant shutdown and first it will be stored in 1200 m3 tank before mixing with low strength w.w., Equalization will be performed in separate 500 m3 equalization tank equipped with mixer. As I mentioned before a flow control valve provided in H.S.W.W. line to operator can change flowrate based on reading of COD in outlet of equlization tank.
I did a prelimanary material balance for different cases you can find below:

Please let me know if you need more information.

Assumptions:

Low Strength W.W.

Flowrate(Min.) 10 m3/hr
Flowrate(avg.) 10 m3/hr
Flowrate(Max.) 20 m3/hr
COD(Min.) 500 mg/lit
COD(Max.) 1000 mg/lit

High Strength W.W.

COD(Min.) 10000 mg/lit
COD(Max.) 20000 mg/lit

Effluent

Flowrate(Min.) 10 m3/hr
Flowrate(avg.) 10 m3/hr
Flowrate(Max.) 20 m3/hr
COD(Min.) 500 mg/lit
COD(Max.) 1000 mg/lit

High Strength W.W. Flowrate Calculation:

Case-I - Low Strengh W.W. COD>=1000 mg/lit
Flowrate 0 m3/hr

Case-II - Low Strengh W.W. COD=500 mg/lit & H.S.W.W COD=10,000 mg/lit.

Flowrate 0.56 m3/hr(Based on L.S.W.W. Flowarate =10m3/hr)
Flowrate 1.11 m3/hr(Based on L.S.W.W. Flowarate =20m3/hr)

Case-III - Low Strengh W.W. COD=500 mg/lit & H.S.W.W COD=20,000 mg/lit.

Flowrate 0.26 m3/hr(Based on L.S.W.W. Flowarate =10m3/hr)
Flowrate 0.53 m3/hr(Based on L.S.W.W. Flowarate =20m3/hr)

Case-IV - Low Strengh W.W. 500<COD>1000 mg/lit

Flowrate 0-1.11m3/hr(Based on H.S.W.W. Flowarate =10000 mg/lit)
Flowrate 0-0.53m3/hr(Based on H.S.W.W. Flowarate =20000mg/lit)

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Dante625 YaBB Newbies Offline I love Water and Wastewater.com Posts: 5 Company or Organization: dfdf	Re: Mixing of two different COD wastewater Reply #10 - Apr 30^th, 2012, 11:51pm I think there is some sort of control over the two waste streams, I would predict that you couldn't accomplish your objective. For more information Please Visit
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alexisrois YaBB Newbies Offline I love Water and Wastewater.com Posts: 10 Gender: Company or Organization: alexisrois co.	Re: Mixing of two different COD wastewater Reply #11 - May 3^rd, 2012, 6:43am Your waste water needs something more powerful than environmental fresh air to deal with the COD issue. Sometimes, suspended solids are a big aspect of the issue & can be resolved or filtered out. If not, you will require to use a more powerful oxidizer, such as peroxide or bleach.
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