Water and Wastewater.com Help Forums - Scum & foam in clarifiers

Joni Ashton

Guest

Scum & foam in clarifiers
May 29^th, 2002, 11:25pm

We have an excellant wastewater treatment plant designed by Aero-Mod, Inc. out of Manhattan, Kansas. We were doing fine until we begged the hotel/casino to take care of their grease problem which in turn became our problem.

After a microbial grease-eating enzyme was introduced to the casino/hotel and their lift station we began to have a lot of foam at our plant. It has the color and characteristics of Nocardia but is not.

We figured the aesthetics may not look so great but our plant (activated sludge process) was doing ok to very good. However we have had major foam turned to nasty scum in our clarifiers. We had to have this skimmed out about a month ago, but the effluent was nice and crystal clear.

If anyone out there has had a challenge like this please contact us and we can dicuss.

Thanks
Joni Ashton
jashton@ak-chin.nsn.us

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KSPRASAD

Guest

Re: Scum & foam in clarifiers
Reply #1 - Jun 3^rd, 2002, 2:01pm

Dear Sir

The foam problem in waste water treatment plant is most recent one. We are also having one of the best waste and sewage water plants in India. The treated water is being passed through Reverse Osmosis process and the permeate water is fed into boilers and cooling towers.

Your problem seem to be generated by reaction with residual oil & grease with some alkali. Mostly this problem can be solved by installing DAF ( Diassolved Air Floation Unit) where Lime, Alum and polymer are dosed before passing through DAF.

Later on in secondary clarifier by adjustmenmt ofrecycling percentage of sludge foamgeneration can be minimised. Also as mentioned in Medcoff & Eddy book slight dosing of NaOcl also reduces the foam generation.

Also wherever possible the discharge pipe should be dipped into the tank to reduce the foam generation.

I think these measures will reduce to some extent teh foam generation in the secondary clarifier

Please confirm the receipt.
Thanks
KSPRASAD
I-49, FF
SOUTH CITY-2
GURGAON-122001
HARYANA
INDIA
PHONE= +91-124-6219436
Email- ksprasad@maruti.co.in, shivaganti @yahoo.com

Thanks

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B.Saki Guest	Re: Scum & foam in clarifiers Reply #2 - Jun 5^th, 2002, 4:57am What I suggest is to try the followings 1-adding a defoamer (silicon base or emulsified parafin if not restricted by local authorities). 2-using an oil emulsifier like Aerosol OT (solution of sodium dioctylsulfosuccinate in isppropanol).
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Marcos De La Monja Carter Guest	Re: Scum & foam in clarifiers Reply #3 - Jun 5^th, 2002, 1:26pm You can resolve your problem instaling a DAF Clarifier as primary treatment if you send us the flow we can quote you one. Thank You Marcos de La Monja Carter
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Jackie Killings

Guest

Re: Scum & foam in clarifiers
Reply #4 - Jun 17^th, 2002, 6:18pm

Your problem sounds like it is caused by filamentous organisms, probably Microthrix parvicella. This filament loves oil and grease. Defoamers will not work on foam caused by filamentous bacteria.

I would suggest a couple of things. First, you can waste some of the filamentous out of the system in your WAS. Also, chlorine will kill some of the bacteria. This is the quickest way to rid yourself of the filament. The chlorine needs to be added in a turbulent area in your system. You should start seeing results within a day or two.

You must be careful about overdosing the system with too much chlorine. You can also destroy your "working" microbes and can cause a turbid effluent.

A source of information is the Manual on the Causes and Control of Activated Sludge Bulking and Foaming.

I hope this helps.

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KSPRASAD Guest	Re: Scum & foam in clarifiers Reply #5 - Jun 18^th, 2002, 3:28am I would support Mr. Kilings views. Foam can be generated due to sludge bulking and can be removed by chlorination.
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Sandeep Patwardhan Guest	Re: Scum & foam in clarifiers Reply #6 - Jul 14^th, 2002, 1:30pm Dear Sir Yours is a common problem as we occasionally have in our activated sludge process in India. The simplest solution is to add silicon antifoaming agent which will get rid of the foam. Also draining off a calculated amount of sludge to drying beds will also reduce skum formation. Regards Sandeep
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P. Vinsant

Guest

Re: Scum & foam in clarifiers
Reply #7 - Jul 18^th, 2002, 2:57am

i agree, if your set up for it, nuke your ditch with chlorine. i am constantly fighting foam in my oxy ditch, and i inject chlorine into my RAS, wich is an ideal location. It doesnt take much, start out conservative obviously....i generally see results in a week or less. My foam is also hand in hand with poor settling. After i chlorinate the problem goes away for oh 3-6 months. Some warning signs of overdoing it are drop in eff. ph and quality. Well im definately no expert i just run a one man show at a 225k oxy ditch plant, but thats my .02....

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