Floating Sludge and Brown Foaming 2

[zavier98]

I recently joined a waste water treatment company where there is a client has a problem of floating sludge in the WWTP of a drinks industry. We are supposed to upgrade its existing WWTP to obtain a higher discharge effluent. After the upgrading from a batch system to a continous system comprising of a activated sludge reactor to a clarifier. Now, we face the problem where the sludge is floating up. I was told that the bacteria floated up because it's either dead or too old. However, the sample i took for SV30 also shows that the sludge is floating up partially. Even if it settle but then after an hour it will float up again. May i ask why is the sludge floating up ? and what are the causes of the floating sludge. Is it dead and too old or is there any other possiblities. and i wish to know more about activated sludge. I will be grateful if u guys can tell me of the possibilities and any other informations will be much appreciated. This situation has been dragging too long so i hope can resolve the problem as quickly as possible. and will the dead bacteria be a food to the bacteria. And another scenario which has happened was the brown foaming all over the activated sludge reactor. Can anybody tell me why ?

 

[oxilume]

zavier98,

Dissolved air flotation (DAF) or induced gas flotation (IGF) maybe the solution to your problem. Likewise, the "floats" can easily be dewatered or decomposed insitu.


Todd

http://www.oxilume.com

 

[jproj]

Floating sludge in the secondary clarifier is generally caused by denitrification. As sludge is held (and not pumped out or recycled), bacteria use any remaining oxygen. After the oxygen is consumed, the system turns anoxic and denitrification occurs (nitrates are consumed by the bacteria and nitrogen gas is released). As the nitrogen is released (as gas) it rises to the top of the clarifier, carrying settled sludge with it.

If denitrification is the problem, the sludge is being held in the clarifier too long. You need to either increase your return activated sludge (recycle) flow rate, of increase your waste activated sludge flow rate / pumping time.

You may also want to check the solids retention time of the activated sludge tank and or the types of organisms in the activated sludge tank. SRT's that are too high or too low can shift biological populations, which influence floc settleability in the secondary clarifier.

Good luck!

jproj

 

[freebo]

zavier98,
I agree with jproj, your 'popping' sludge is probably due to denitrification and the RAS a/o WAS should be increased. As to the foam problem - you need to take a closer look at the activated sludge, like through a microscope. The foam may be caused by various things including filamentous bacteria. What sort of 'drinks' industry is this?

freebo

 

[latinchem]

zavier98, I agree with jproj and freebo, the best way is to look through a microscope. The filamentous bacteria (usually ones called sphaerotilus nathans) look just like filaments. But another tip: I had filamentous bacteria problems in my treatment plant and I also had a denitrification problem in the clarifiers. In both cases there was foam but only in the second the foam was brown. Anyway the microscope will solve the mistery.
P.D.: sorry for my english.
Good luck,
Vergenie.

 

[ema]

As everybody said, first thing to do is examination through microscope. Please also check F/M ratio with your design parameters. DO in your aeration tank could also be low that will result in growth of filamentous organisms. Manipulating your sludge draw off rate from your clarifier could be a solution.

If you have nocardia foam (if you have high fat and grease content, common in beverage industry), you might also need to monitor your pH in aeration tank. Low pH values will increase the growth of nocardia.