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Biological Phosphorus removal
Apr 30^th, 2012, 1:19am

Hi,

We want to maximize the biological P removal of our industrial waste water plant.
One way that has been suggested is to open the influent valve to our anaerobic zone to increase the HRT in the anaerobic and anoxic zones. Would allowing influent into the anaerobic zone (usaully just the RAS from the clarifier) make it then an anoxic zone?
Then if this was the case, would this help or hinder P removal?

cheers
Smiley

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BendelBoy

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Re: Biological Phosphorus removal
Reply #1 - Apr 30^th, 2012, 3:24am

Do you have any nitrate in your influent? If not, then it will be no more anoxic than it currently is.

What is the dissolved oxygen level in the influent? How does the influent enter the tank? (I have seen some influents end just above the water level, turning them into plunging jet aerators - not good if you want an anaerobic or anoxic zone.)

Do you have any anaerobic zones?
Do you have enough volatile fatty acids?
Do you have a sufficient HRT & SRT?
Lots of questions.

Some basic modelling might help you understand what the effect of any proposed changes might be.

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The sludge judge

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Re: Biological Phosphorus removal
Reply #2 - Apr 30^th, 2012, 10:49am

I think I understand what your saying. You're currently operating in contact stabilization mode and want to turn your first zone into a selector. This will generally lower the ORP and promote biological phoshorus removal provided the necessary conditions exist.

We need some data to help you. What are the COD and the Phoshorus in the influent? What are the influent Volatile Fatty acids concentration? What is the current retention time in this tank and what will it be if you add the influent to it? What is the ORP in this tank? What type of waste are you treating? What is your phoshorus limit and what's your outgoing orthophoshate right now?

best regards,

Ryan

ps- I like your areas of expertise! Is "football" referring to soccer or American Football. A nice homemade Australian brew sounds good right about now.

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sludge_man

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Re: Biological Phosphorus removal
Reply #3 - Apr 30^th, 2012, 10:45pm

Do you have any nitrate in your influent? If not, then it will be no more anoxic than it currently is. - Yes Influent contains nitrate average 1 mg/L

What is the dissolved oxygen level in the influent? - we have never measured influent DO, would assume low given the influent streams have to travel down the underground pipe network.How does the influent enter the tank? Influent enters the tank around 1/2 way up a 5-6 m deep tank(I have seen some influents end just above the water level, turning them into plunging jet aerators - not good if you want an anaerobic or anoxic zone.)

Do you have any anaerobic zones? Our 1st zone contains only RAS from the clarifier, 2 and 3rd zones are were the activated sludge contacts the influent under conditions without oxygen. then we have the aerobic zone. Then we remove sludge with a clarifier
Do you have enough volatile fatty acids? VFA's should be fine, influent composition is brewery waste meaning short chain fermentables are present
Do you have a sufficient HRT & SRT? HRT influent spends about 45mins in no oxygen zone then 4.5 days with oxygen. Unsure what is ideal? SRT we try to keep low to favour younger organisms for P removal. But dont have a VSD to control amount of sludge wasted.

Cheers

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sludge_man

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Re: Biological Phosphorus removal
Reply #4 - Apr 30^th, 2012, 10:54pm

I think I understand what your saying. You're currently operating in contact stabilization mode and want to turn your first zone into a selector. This will generally lower the ORP and promote biological phoshorus removal provided the necessary conditions exist.

We need some data to help you. What are the COD and the Phoshorus in the influent? COD average 970 TP influent 14.8 mg/L TN 17.2 What are the influent Volatile Fatty acids concentration? Unknown waste is brewery waste should contain short chain carbon products What is the current retention time in this tank and what will it be if you add the influent to it? current retention time in zones without oxygen is ~45mins could be extended to ~ 1 hour with proposed changeWhat is the ORP in this tank? Average -162 mV What type of waste are you treating? brewery waste - water from tank washing process water line flushing, beer, sweet wort etc. What is your phoshorus limit and what's your outgoing orthophoshate right now? limit is below 1mg/L TP average around 5mg/L right now

thanks for help
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The sludge judge

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Re: Biological Phosphorus removal
Reply #5 - May 1^st, 2012, 1:32pm

Most literature I"ve seen suggests you want a soluble COD to P ratio of around 45:1. It's possible you may be a little bit COD limited in getting complete bio P removal and may have to chemically remove what's left over. It is important to filter this and make sure your remaining P is in the form of orthophoshate and not bug bodies (TSS)

It appears you're getting some degree of biological phosorus removal already based on removing more than I would expect for just nutrient demand. (Do a neisser stain to judge the abundance of your PAOs)

How are you running the 2nd and 3rd anaerobic/anoxic cells- in series or in paralell?

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sludge_man

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Re: Biological Phosphorus removal
Reply #6 - May 1^st, 2012, 7:38pm

Thanks again for your help clarifier suspended solids averages around 25mg/L

Thanks for the idea of the neisser stain, we will try this and see how we go.

2nd and 3rd zones are in series (the same tank just baffles between them to facilitate mixing etc) So what I was wondering was that if the first zone (whcih currently only contains RAS from the clarifier) was changed to be an extension of zones 2 and 3 (by allowing influent in there). Could we get more by increasing our retention time in these zones?

Or does the current set up theoretically provide the best way to remove P?

cheers
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The sludge judge

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Re: Biological Phosphorus removal
Reply #7 - May 2^nd, 2012, 12:36pm

How much nitrate is in each of the anaerobic/ anoxic zones?

Feeding the influent to both #1 and #2 may help provide a zone for denitrification (#1) and then a zone for orthophoshate release and VFA uptake (in #2). #3 would end up acting as an extension for #2. It's worth a shot if nothing else. Monitor your ORP in each and see if you can get them closer to -200 mV.

I don't believe you'll get any denitriifcation without any food (your influent) in #1. I'm not sure the purpose of mixing the RAS in an unaerated tank. It may be worth tinkering a bit.

1000 mg/L COD seems low for a brewery. Is there an anaerobic pre-treatment step involved first?

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