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Ashoori Ex Member	BOD, COD higher than influent of aerated lagoon!? May 10^th, 2012, 12:30pm Hi Experts We have an aerated lagoon which BOD and COD is higher than influent. Would you help me to find the problem? Could it be because of overloading? or may be an industrial wastewater is entering the municipal wastewater? I`ll be so thankful. Regards Ashoori
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grrun

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Re: BOD, COD higher than influent of aerated lagoon!?
Reply #1 - May 10^th, 2012, 4:08pm

What are the differences in results between influent and effluent?

Where in the WWT process is the lagoon? If it is in the beginning of the process, I would think that aeration might suspend some solids which might increase the effluent COD and may cause an increase in BOD.

To check this hypothesis, I would test for soluble COD on both the influent and effluent and TSSs on both the influent and effluent. I'm uncertain what tests to perform for the BOD increase other the change in COD and TSSs.

grrun

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The sludge judge God Member Offline Posts: 649 Wisconsin Gender: Company or Organization: private	Re: BOD, COD higher than influent of aerated lagoon!? Reply #2 - May 10^th, 2012, 4:25pm Check the soluble COD and BOD on the effluent as well as cBOD. Nitrification in the BOD test may make it read higher or you may have have particulate BOD (solids, algae etc). Once this is known, more advice can be offered. best regards, Ryan
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C. Gillen God Member Offline Applied Environmental Biotechnology Posts: 773 Ireland Gender: Company or Organization: BioFuture Ltd.	Re: BOD, COD higher than influent of aerated lagoon!? Reply #3 - May 11^th, 2012, 8:07am Hi Ashoori, I would agree with the comments from Ryan and grrun. Is it possible that you had a shock loading come through the lagoon? If so there should have been a reduction in DO and possibly some evidence of foaming. Check also for evidence of short circuiting. Best regards, Cgillen
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sobisch God Member Offline Posts: 1777 Gender: Company or Organization: L.U.M. GmbH	Re: BOD, COD higher than influent of aerated lagoon!? Reply #4 - May 11^th, 2012, 9:05am Dear Ashoori incidents of higher COD and BOD in aerated lagoon may occur from time to time due to mobilization of deposits. These may be triggered by higher influent or temperature variations. Kind regards T. Sobisch
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Tom Keenan - nesa God Member Offline Environmental Consultant - contact info@nesa.ie Posts: 2103 Gender: Company or Organization: nesa environmental consultants	Re: BOD, COD higher than influent of aerated lagoon!? Reply #5 - May 11^th, 2012, 6:00pm Is it the contents of the aerated lagoon, or the discharge from the lagoon, that has higher BOD - COD than the influent?
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Re: BOD, COD higher than influent of aerated lagoon!?
Reply #6 - May 11^th, 2012, 8:32pm

Ashoori:

You need to test the effluent for total and soluble BOD and TSS. If the soluble BOD is high, then you may have a break-through of untreated BOD (bad). If the soluble BOD is low but the total BOD and TSS are high, then you have a solids loss problem. Then you need to have the effluent examined microscopically. Typical solids loss problems are biomass (bacterial flocs); algae; old benthic sludge; and sulfur bacteria.

Hope that this helps.

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