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kashifshabbir Full Member Offline I love Water and Wastewater.com Posts: 210 Company or Organization: westpoint home	how Nitrification reduce Unoxidized Organic Matter Sep 03^rd, 2012, 4:18pm Dear friends, Can anyone explain in brief how Nitrification reduce unoxidized organic matter in activated sludge treatment plant. Thanks and Best Regards, KS
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DS God Member Offline sapere aude Posts: 1581 Company or Organization: Indept. Freelance Consultant	Re: how Nitrification reduce Unoxidized Organic Matter Reply #1 - Sep 3^rd, 2012, 5:07pm Hi Kashif, can you explain a bit more your question, and waht you want to achieve?
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Re: how Nitrification reduce Unoxidized Organic Matter
Reply #2 - Sep 3^rd, 2012, 6:14pm

I think that you might be referring to denitrification under anoxic conditions. Initially, ammonia is oxidized to nitrite/nitrate under aerobic conditions; then the nitrate can be used by denitrifying organisms (under anoxic conditions) to oxidize soluble organics. The nitrates are reduced and may be released as a gas. There are several treatment schemes that promote these reactions.

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kashifshabbir Full Member Offline I love Water and Wastewater.com Posts: 210 Company or Organization: westpoint home	Re: how Nitrification reduce Unoxidized Organic Matter Reply #3 - Sep 3^rd, 2012, 6:45pm Thanks DS and grrun for reply, Its mean During Nitrification no stabilization of unoxidizd OM occure ? How we can promote denitrification in the reactor instead of clarifier ? Regards, KS
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Re: how Nitrification reduce Unoxidized Organic Matter
Reply #4 - Sep 3^rd, 2012, 7:25pm

To the contrary, with the right conditions, both ammonia and organics are oxidized. You may be able to cycle the aeration basin between aerobic and anoxic conditions.

Incidentally, if there are no organics to oxidize, then denitrification will not occur. If denitrification is occurring in the clarifier; then nitrates and BOD are present along with low DO. Is your question, "How to prevent denitrification in the clarifier?"

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DS

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Re: how Nitrification reduce Unoxidized Organic Matter
Reply #5 - Sep 4^th, 2012, 1:08am

denitrification can take place either with extracellular (readily) biodegradable COD (often fast kinetics), and/or with intracellular COD like PHB (with PHB: can be pretty fast, but not allways) or even with lysis products from biomass decay (slow kinetics).

you should promote denitrification prior to sludge settling by implying the conditions: (1) nitrate (e.g.: through nitrate recycle) + (2) sludge present in (3) the absence of oxygen, (4) in the presence of enough COD, and all previous 4 conditions: (5) long enough in order to achieve enough reduction of nitrate (often the kinetics are limiting). using readily biodegradable COD, the kinetics are fast, hence a smaller reactor or a shorter time will be required to achieve the desired reduction of nitrate-N.

most used lay-out in continuous systems is pre-denitrification in which the RAS is cycled to an anoxic (unaerated but mixed) tank ahead of the aeration tank and in which the influent (COD) is fed together with a recycle flow (nitrate) from the aeration tank.

hope this helps,

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Re: how Nitrification reduce Unoxidized Organic Matter
Reply #6 - Sep 4^th, 2012, 1:33am

Hi,

How we can promote de-nitrification in the reactor instead of clarifier?

The most common method the treatment facilities design engineers prefer is; Introduction of ANOXIC with a low speed Mixer, installation of mixed liquor pumps to return the nitrates to the anoxic zone from the far end of the aerobic zone to enhance de-nitrification.

If you don't have this flexibility, then try to create Anoxic Zone at the inlet of the reactor by adjusting the air flow rate if diffused aeration or switch off first row aerators if surface aeration . This will work out to some extent but needs close monitoring

DS has given a much better explanation !!!

Regards ,

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DS God Member Offline sapere aude Posts: 1581 Company or Organization: Indept. Freelance Consultant	Re: how Nitrification reduce Unoxidized Organic Matter Reply #7 - Sep 4^th, 2012, 1:57am Hi, these are indeed possible ways to implement an anoxic zone in existing sitations, and care must be taken that sludge doesn't settle due to a lack of effective mixing. best regards, DS
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AZS Senior Member Offline Water and Wastewater.com is the best! Posts: 264 Gender: Company or Organization: OIL, GAS & UTILITIES	Re: how Nitrification reduce Unoxidized Organic Matter Reply #8 - Sep 4^th, 2012, 2:08am Agreed DS Air Flow regulation was done intermittently to avoid sludge settling /anaerobic conditions. regards,
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DS God Member Offline sapere aude Posts: 1581 Company or Organization: Indept. Freelance Consultant	Re: how Nitrification reduce Unoxidized Organic Matter Reply #9 - Sep 4^th, 2012, 2:18am Hi zaffrulla, intermittent aeration may not allways (or often not; this depends on a lot of factors) be sufficient to avoid settling of sludge. I've seen sludge layers of 2.5 m thick in aeration tanks of 4 m deep (water height), due to intermittent surface aeration.
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