Foam Control in WWTP

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Foam Control in WWTP

What is the best ​chemical ​treatment to ​reduce foaming ​caused by ​filamentous ​bacteria in ​wastewater ​plants?
The process in the plant where I work is composed of classic primary sedimentation, denitrification before oxidation, secondary sedimentation and disinfection.

When the temperature of sewage inlet drops down to 15°C there is a gradual increase of foam growth in the oxidation.

The operating conditions in the anoxic selector are HRT=3.5-4 h without flow equalisation. At the moment we’re dosing AlCl3 to coagulate PO42- and reduce the foaming.
Please find the attached picture of bacteria viewed with a microscope. 

What kind of chemical products should I use to eliminate or reduce the foaming?

In the area where I live and work we can’t use NaOCl.

Thanks and Best Regards,
Matteo

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20 Answers

  1. Frenc English

    Bonjour la bactérie filamenteuse n'existe pas c'est une pure imagination de l'esprit de la part de gens qui n'ont pas su reconnaitre toute la filasse, les cheveux, le déchiquétement des tissus qui sont injectés dans les eaux usées.

    En plus l'effluent d'eaux usées est tellement contaminé par tous les produits chimiques qu'ils contiennent que plus aucune bactérie n'est active.

    Les boues sèches des stations STEP contiennent plus de 8% de bactérie morte. Une abération quand on sait que d'un point de vue - biologique- une bactérie morte cela n'existe pas. Seule une bactérie vivante détruit une bactérie morte tout en récupératn une parie de la pile énregétique de celle ci.

    English

    Hello filamentous bacteria does not exist it is a pure imagination of the spirit on the part of people who have not been able to recognize all the bast, the hair, the shredding of the tissues that are injected into the waste water.

    In addition the wastewater effluent is so contaminated with all the chemicals that it contains that no bacteria are active.

    The dry sludge of the STEP stations contains more than 8% of dead bacteria. An abortion when we know that from a biological point of view - a dead bacterium that does not exist. Only a live bacterium destroys a dead bacterium while recovering a bet of the energetic pile of it.

  3. Matteo,

    Can you give us an update? As you had stated in your micro analysis there was no filamentous (M.Parvicella, Nocardia) so am confused as to why people recommend solutions to control these organisms. Have conditions changed?

     

    1 Comment

    1. Hi Tom,

      I did an additional microbiological analysis but I didn’t find filamentous bacteria. The foam is not caused by surfactants ad you can see on the photo.

      The foam is always there, we remove it with a canal jet machine and we continue to dose PAC to prevent growth on filamentous bacteria.

       

  4. I agree picture does not show Nocardia or Parvicella, sludge looks good slightly into endogenous respiration. Do you have any industrial wastewaters dumping surfactants?

  5. French english

    Les bactéries filamenteuses n'existent pas. il s'agit tout simplement des fils de lingerie auxquels il faut ajouter les poils et les cheveux.

    Les eaux usées du collectif contiennent des milliers de litres de produits contenant des molécules chimiques. plus aucune bactérie ne survit dans un tel milieu quand en plus le système en ait d ela boue en putréfaction.

    La mousse provient essentiellement de la putréfaction

     

    The filamentous bacteria do not exist. It is simply the sons of lingerie to add hair and hair.

    The collective wastewater contain thousands of liters of products containing chemical molecules. most bacteria don't Rogers in such an environment when more en ACI d ela rotting mud system.

    The foam is essentially due to putrefaction

     

     

    1 Comment

  6. By looking at your photo, it looks like that your foaming problem is not due to hydrophobic filamentous organisms such as nocardioform or M. parvicella. I can't really see any filamnetous organism there! If your foam would be due to excessive EPS production, it would look like a white light foam, similar, but less persistent than foam caused by non-biodegradable surfactants. You may show a photo of your foam, to get more info.

  7. In my experience biological foaming in most cases is due to nocardioforms. Filamentous bulking and foaming can be controlled by various specific and nonspecific strategies. Specific control strategies are preferable as they are selective and offer a permanent solution of the problem whereas non-specific methods tend to provide only temporary solutions. Non-specific methods like, use of oxidizing chemicals are currently the only available strategies for effective foaming control and it can be applied in all WWTP. However, use of high chlorine doses may inhibit both nitrification and organic matter removal and cause floc break-up Therefore, based on evidence provided by microbiological observations .it can be concluded that chlorine remediation of foaming provide only temporary and superficial way for the treatment of wastewater containing oil and grease. the floc even after the chlorine application and maintains its potential for excessive growth .Higher aeration basin temperature provides favorable conditions for the growth of Nocardia while M. parvicella grows at lower temperatures. Due to the physical interlocking of the filaments in the foam provides stability to the foam and this type of foam is difficult to remove by antifoam chemicals. Nocardia and M.parvicella bacteria are tolerant to chlorine and are found within the flocs so, high chlorine dosages required for this type of foam control.

  8. Thanks for your replies.

    I checked by microscope sludge and foam yesterday, but surprisingly I didn’t find anything unusual as you can see in the photo. There were no filamentous, no M. Parvicella or Nocardia. I only saw that the sludge’s floc is little.

    The sludge sedimentation is good and the SVI index is about 80-100, but the foam is growing little by little so we need constantly remove it.

    Could the foam be the cause of industrial discharges, low temperature in the oxidation tank (12°C) or an incorrect airflow?

    Thanks. Matteo

    2 Comments

    1. If it's not filamentous, then either Surfactants, Nutrient imbalance, fines from an anarobic digester, or Toxicity.

      What is the appearance of the foam?  Is it white or brown, stiff or billowy or slimy?  Surfactant foams are usually lighter color and billowy.  It's good to keep a couple of different defoamers on hand to try, to see what's effective for this. 

      Nutrient imbalance is something to look at as well.  Do you calculate the C:N:P ratio on your Influent?  If the foam is slimy and you do an india ink test under the microscope you should be able to tell if polysaccharides are building up in the floc, which is an indicator for this.

      Another possible cause of foam is toxicity, but your microscope photo looks OK.  Just to check though - are you seeing  Ammonia levels rise, or cloudiness in your Clarifiers/DAF ? 

       

    2. If foaming is serious, dosing anti-foam chemical is the fast way to control foaming.

      you can check whether the foam is caused by surfactant discharged by industries. just take some influent and aerate, if you see foaming, then can we can confirm it is surfactant. if no foaming, then we can rule out the possibility.

      if it is not caused by surfactant, then we can optimize the operation using methods suggested by other here, such as aeration, SRT, etc.

      1 Comment reply

  9. Matteo:

    I agree with others' comments - find out which Filamentous organism is causing the problem (probably Nocardia or Microthrix), reduce FOG in the Influent, reduce Sludge Age (MLSS) if possible while keeping good treatment, remove as much of the foam as possible from all basins (the foam is filamentous bacteria, not a by-product).   A note on the Anoxic selector - at my plant, we use an Anaerobic selector for filamentous control and it works very well.  The HRT is 2 hours - when we drop below this, the foam levels definitely go up.  If possible it may be helpful to run the ORP lower in your selector.  Ours normally runs below -350 mV.     Best of luck.

    Leah

  11. Mateo:

    It sounds like you might have had this pop up quickly.  If so then it might have been due to a quick temperature change.  To minimize impacts at this point with no use of NaOcl then try using a water spray to get the Nocardia down into the water and let the bugs eat it up.  Reduce the amount of air since that is what Nocardia thrives on.  once the foam is reduced then get the correct amount of MLSS into your system.  Keep it balanced and it will ride thru the temperature changes.  

    Keep your bugs happy and everyone working there will be happy.

    good luck sir,

    Lyman Waller 

  14. try bioaugmentation.  easy and simple and quick.

    1 Comment

    1. Bioaugmentation will not correct an imbalance in the species mix in the activated sludge process, unless you want to add tonnes of bacteria continuously. If the conditions are right, the right bacteria will grow. If conditions are wrong any bacteria you add will not survive for long.

  15. I think rather than using chemicals, I would optimise the aeration to only have sufficient oxygen in the reactor, lower the sludge age if it's too high, and ensure adequate food to microorganism ratio to try and combat the filamentous and Nocardia bacteria.

  16. Hi. Matteo. Its best foam is dealt with separately an all that floats is scimmed away. Now check the P and C constituents of the scum and liquid & deal with this... chemically. In this way the contaminants stay separate.. w wshs Ajit Seshadri... seshadri.ajit@gmail.com ... 

  17. First thing is to get the filaments identified.  If it is nocardia, then the best way to deal with it is managing it as opposed to trying to kill it.  It is a constant battle with nocardia.  Here in the UK we tend to find nocardia due to the influent characteristics containing FOG, typically in tourist catchments with a high density of hotels, B&Bs, restaurants etc.  You need good trade effluent management, the properties need to keep their grease traps well maintained.  Even with this the inlet works will still need FOG removal and it is best to have a classifying selector. This is not your traditional type of selector - a floating boom in the aeration lane which the operator can isolate and remove the moose which contains the nocardia.  This type of device is still quite novel but easy to build in for new builds.  By removing it this way you are in effect managing it but at a lower cost than constantly dosing something into the process. Nocardia is more a nuisance than a problem especially in warmer months when it can crust over and cause foul odours.

  18. Dear Matteo

    At Aqwise we install anti-foam systems only in industrial plants. Those systems, designed by Aqwise, are automatically controlled by an optic eye located in the reactor. Important to use chemicals based on water and not silicon or other compound. 

    In municipal plants we do not have such problems, and if there are signs of "foam", specifically in the anoxic stage, it is usually due to not sufficient de-nitrification.

    Zoli

  19. In my experience biological foaming in most cases is due to nocardioforms or Microthrix parvicella. M. parvicella tend to disappear after dosing polyaluminum chloride, but this may not happen is foaming is due to nocardiform organisms. Also it may take at least three times the SRT (sludge retention time). One other way is to selectively discharge foaming from the top of the oxidation basin by an adjustable overflow baffle. This flow should be accounted for as additional waste sludge. A reduction of the exraction from the secondary settling may be necessary to avoid the washout of nitrifiers, especially at low temperatures. A second option is to apply ozone to a fraction of the sludge recycle flow (see Gardoni D., Ficara E., Vergine P., Canziani R. (2015) A full-scale plug-flow reactor for biological sludge ozonation, Water Science and Technology, 74(4), 560-565. doi: 10.2166/wst.2014.432, attached). I hope this info may be useful.

    1 Comment

  20. Dear Matteo, 

    May be you are living close to Venice and for this reason bleach could not be used. If you have filamentous bacteria one of the system that I used many time ago into a food plant was to dose on the sludge ricirculation glutaraldeide at 25% at 5 ppm. In this manner it was possible to reduce the filamentous concentration  and the foam was reduced.

    Maybe you can try dosing less only 2-3 ppm and check by microscope. An overdose of PAC can also increase de sedimentation of the filamentous but it is not always an advantage for foam but if you need to reduce P content there are not alternative.

     

    Good luck

    1 Comment

    1. Hello Mateo,

      one of the factors favoring the foaming of biological muds is the production of sulphides in the primary decanter. Indeed the filamentous typical bacteria Thiotrix feeds on sulphides!
      To remedy the moussage we can envisage three points of action:
      1 to limit the concentration of primary muds in 10g / l of MS by frequent extractions,

      2 to inject of the FeCl3 into the entrance(entry) of the zone anoxia to trap sulphides,

      3 if need be handle punctually muds of the pond of aeration with a solution of whitewash in 5g / l to block(surround) the moussage of surfactants.

      Sorry for my bad english !!