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asdwe

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Equalization tank effluent concentration
May 28^th, 2012, 10:10am

Hello,

I am try to design an equalization tank for Wastewater treatment plant which means that the ET will be placed before the process. I have statistics about the influent BOD concentration and flow rate. I calculated the Volume of the tank but I couldn't find the effluent BOD concentration. So could you please help me to know the way of calculating it.

this is a sample of the concentration and flow rate

time (hr) flow rate in (m3/hr) BOD (mg/l)
0-1 4000 200
1-2 3000 130
3-4 3500 250
4-5 4500 230

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Jeff Naumann God Member Offline I love Water and Wastewater.com Posts: 1133 Torrance, California Gender: Company or Organization: Jeff Naumann & Associates	Re: Equalization tank effluent concentration Reply #1 - May 28^th, 2012, 10:21am What about the period from 2-3?
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asdwe YaBB Newbies Offline I love Water and Wastewater.com Posts: 4 Company or Organization: None	Re: Equalization tank effluent concentration Reply #2 - May 28^th, 2012, 11:26am Ops, I missed this line, that will be 2-3 2500 200 thanks
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Tom Keenan - nesa

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Re: Equalization tank effluent concentration
Reply #3 - May 28^th, 2012, 12:17pm

Hi
If you collected all of the listed flows in a single tank you would have:
a) 4,000 m3 at 200 mg/l = 800 kg
b) 3,000 m3 at 130 mg/l = 390 kg
c) 2,500 m3 at 200 mg/l = 500 kg
d) 3,500 m3 at 250 mg/l = 875 kg
e) 4,500 m3 at 230 mg/l = 1,035 kg

Totals = 17,500 m3 containing 3,600 kg,
equivalent to a concentration of 205.7 mg/l.

That "should" be the BOD of the mixture.
However, there are many things that must be considered such as bio-degradation of BOD during the collection process, etc.

Really you need to design the Equalization tank on the basis of hydraulic load, and then test the output so that you can know how to control the biological process.

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tomkeenan@nesa.ie
Environmental Consultant
www.nesa.ie

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asdwe YaBB Newbies Offline I love Water and Wastewater.com Posts: 4 Company or Organization: None	Re: Equalization tank effluent concentration Reply #4 - May 28^th, 2012, 12:55pm I thought this should be solved using mass balance method, since the equalization tank is filling & emptying during the day so at time 0-1 the effluent BOD concentration will be different than at time 1-2. Thank you
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Jeff Naumann

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Re: Equalization tank effluent concentration
Reply #5 - May 28^th, 2012, 2:08pm

You need to consider what the flow rate during treatment will be; and, over how many hours per day, days per week, etc. Normally, when designing an equalization tank the goal is to be able to treat the waste at a relatively constant rate, over at least the average daily flow, if not the maximum daily flow. That's the ideal case. But, the type of treatment process and characteristics of the waste also enter into the problem.

What, exactly, are to trying to accomplish? What type of waste is this? What type of treatment system? What effluent limits will be needed to be met?

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Jeff Naumann God Member Offline I love Water and Wastewater.com Posts: 1133 Torrance, California Gender: Company or Organization: Jeff Naumann & Associates	Re: Equalization tank effluent concentration Reply #6 - May 28^th, 2012, 2:17pm Here is a link to an example that shows how to calculate the needed volume of an equalization tank: http://web.deu.edu.tr/atiksu/toprak/denge1.html
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asdwe

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Re: Equalization tank effluent concentration
Reply #7 - May 28^th, 2012, 3:49pm

The posted link is very helpful, I appreciate your help.

Mr. Naumann, what you said is absolutely correct, and I was wondering how to get the effluent without these kind of information.
this project is all about designing ET for a plant where I live and by only using the information that I mentioned in the beginning. The waste is a domestic waste and pre-treated industrial waste. The treatment system is primary with screening & settling tank, while the secondary is an activated sludge. The effluent limits needed to be met is not available.

Thanks to you and to Mr. Kenaan

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