Water and Wastewater.com Help Forums - denitrification and oxygen

zzzbbbdz YaBB Newbies Offline I love Water and Wastewater.com Posts: 23 Company or Organization: NUS	denitrification and oxygen Aug 10^th, 2012, 2:15am my question is: During denitrification, what is the fate the oxygen atom in NO3 and NO2? Or, the denitrification process will provide O2 or not? In design, do we need to consider the oxygen provided during denitrification and as a result, the total oxygen demand is less?
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The sludge judge God Member Offline Posts: 649 Wisconsin Gender: Company or Organization: private	Re: denitrification and oxygen Reply #1 - Aug 10^th, 2012, 5:58am You'll recover about 30% of the oxygen if you denitrify. Per weight for each pound of nitrate (NO3) you'll get 2.9 lbs of oxygen back. best regards, Ryan
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RoCSmith Junior Member Offline Posts: 68 Ohio Gender: Company or Organization: YSI	Re: denitrification and oxygen Reply #2 - Aug 10^th, 2012, 7:39am Biochemically speaking, the oxygen atom in NO₃ goes to CO₂ just like it does when molecular oxygen is consumed. Practically speaking, this results in an oxygen credit of 2.9 lbs. per lbs. of NO₃-N removed as Ryan stated. RS
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tkall

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Re: denitrification and oxygen
Reply #3 - Aug 10^th, 2012, 4:39pm

OK...I'll admit it...I am confused. I don't understand the concept of an oxygen credit during denitrification. The oxygen "consumed" in an anoxic process in similar manner to an aerobic process. For example if I put a plastic bag tightly over my head and breath, there is still technically the same number of moles of oxygen in the bag but it is covalently bound with carbon and therefore unavailable to sustain me. Am I missing something?

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pekasus YaBB Newbies Offline I love Water and Wastewater.com Posts: 5 Gender: Company or Organization: PekaSys, Inc	Re: denitrification and oxygen Reply #4 - Aug 11^th, 2012, 9:27am This is interesting, but I am wondering when you would use this oxygen credit. Since the oxygen is released during denit, the BOD should already be low...so is this credit used to increase the DO of the effluent?
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tkall YaBB Newbies Offline I love Water and Wastewater.com Posts: 4 Company or Organization: kallenbach, inc	Re: denitrification and oxygen Reply #5 - Aug 11^th, 2012, 10:36am Denitrification consumes BOD, but as the oxygen concentration approaches 1mg/L, the rate of denitrification approaches zero. So if free oxygen is present, denitrification ceases. So I am still confused about an oxygen credit unless you mean that denitrification consumes BOD.
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RoCSmith

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Re: denitrification and oxygen
Reply #6 - Aug 11^th, 2012, 11:49am

The oxygen credit applies to the design of the air (oxygen) supply system. BOD is consumed in the uanerated (anoxic) portion of the tank reducing the influent BOD to the aerated portion.

As for CO₂, that is a good question. Us humans can only respire molecular oxygen. Microbes may have a tougher life but at least they have the capability to respire many other compounds.

Cheers, RS

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tkall YaBB Newbies Offline I love Water and Wastewater.com Posts: 4 Company or Organization: kallenbach, inc	Re: denitrification and oxygen Reply #7 - Aug 11^th, 2012, 12:07pm OK...so organics are removed by denitrification, but it is incorrect to suggest that free oxygen is released because the oxygen in the nitrate bonds to the carbon in the organics and the hydrogen in the organics.
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zzzbbbdz

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Re: denitrification and oxygen
Reply #8 - Aug 11^th, 2012, 7:28pm

According to ASM1, the oxygen released during denitri will not contribute the DO concentration in mixed liquor.

we know Denitri will consume BOD or COD and this will be considerred in design, but whether the oxygen credit release from No3 can be used for oxidation of organics as in aerobic zone is a problem.

according to the answers above, the oxygen released seems can not be used for organic oxidation, so the final fate of the oxygen has nothing to do with the COD removal, right? I got different answers for this question.

please clarify it clear, thanks

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RoCSmith Junior Member Offline Posts: 68 Ohio Gender: Company or Organization: YSI	Re: denitrification and oxygen Reply #9 - Aug 13^th, 2012, 6:52am BOD/COD is a measure of organics. Is that what you are asking?
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SludgeHound Senior Member Offline Water and Wastewater.com is the best! Posts: 388 Gender: Company or Organization: Nalco Company	Re: denitrification and oxygen Reply #10 - Aug 16^th, 2012, 7:21am The oxygen one gets back is in the form of CO2 and in water, you get back carbonate alkalinity. Since one need about 7ppm of carbonate alkalinity per ppm NH3 in the nitrification process, the return of carbonate alkalinity during denitrification does help systems maintain the process.
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zzzbbbdz YaBB Newbies Offline I love Water and Wastewater.com Posts: 23 Company or Organization: NUS	Re: denitrification and oxygen Reply #11 - Aug 17^th, 2012, 1:17am So, if the oxygen comes back in the form of CO2, so where is the C in the CO2 comes from, from organic substances in wastewater? In this case, the oxgen can still be used by heterotrophs for oxidation of the organic substances?
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RoCSmith Junior Member Offline Posts: 68 Ohio Gender: Company or Organization: YSI	Re: denitrification and oxygen Reply #12 - Aug 21^st, 2012, 8:09am Actually, denitrifiers are heterotrophs. The carbon source (electron donor) is organic carbon; the electron acceptor is nitrate.
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tkall YaBB Newbies Offline I love Water and Wastewater.com Posts: 4 Company or Organization: kallenbach, inc	Re: denitrification and oxygen Reply #13 - Aug 25^th, 2012, 4:32pm zzzbbbdz No disrespect, but you need to get a book and read up on this subject. I think it would be disrespectful to not tell you that your questions suggest serious lack of basic understanding. I don't think you can advance until you understand the fundamentals.
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The sludge judge

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Re: denitrification and oxygen
Reply #14 - Aug 25^th, 2012, 9:59pm

http://www.wastewaterhandbook.com/webpg/th_nitrogen_43denitr.htm

here's some reading material on denitrification and plant design.

- To the origional poster: don't be afraid to ask questions here, this forum is for learning/ there are no dumb questions. Feel free to pm me off line anytime if you don't feel comfortable posting it.

On another note, I followed this discussion and I think it was beneficial.

best regards,

Ryan

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