Tertiary Treatment Surfactant Foam - Water and Wastewater.com Help Forum

Water and Wastewater.com Help Forum - Tertiary Treatment Surfactant Foam

Question by Hilary - CAMS

We have a modified UCT BNR plant with the recent addition of tertiary treatment. That is, alum dosing, sand filtration and UV disinfection prior to discharge into the local creek.
We are currently experiencing huge amounts of surfactant foam on top of the filters and in the filtered water tank. It is interfering with the level sensors. We have tried using a silicone based anti-foam, which works well prior to filtration, however it is stripped out during filtration and the foam remains in the filtered water tank.
My questions are: are there any other ways of dealing with surfactant foams and will the silicone based anti-foam cause binding of the filter media therefore making it unsuitable for long term use?

Answer

The origin of foams and related problems were discussed several times at this forum. For possible origin and counter measures see for example topic 'foam in aeration tanks'.

I would guess that 'surfactant' is generated during the UCT process in the form of exopolymers. Our experts in this field might eventually comment on this, how to modify the process to reduce the eventual impact.

As discussed previously, there is no foam generation without the generation of bubbles. That means that you should avoid mechanical conditions where bubbles might be generated (flow conditions).

Coagulation and sand filtration should contribute to the removal of foaming substances. Eventually you could optimize the coagulation process to avoid foaming. To this end you will have to conduct some lab tests. A switch to or combination with flocculation might bring better results.

Yes, possibly the silicons will impact the filtration process.
Note defoamers do not remove but add to the chemical load. Why then adding before the water holding tank?

Answer by Ciaran Gillen - Applied Environmental Biotechnology

If you are sure that it is chemical surfactants then it should be possible to remove them in the aeration section. It would be necessary to use bioaugmentation to achieve this. If you can provide some information on the type of surfactants involved then we may be able to suggest a solution.
If this is of interest feel free to contact me.

Regards,
Ciaran Gillen
cgillen@biofuture.ie


Reply by Hilary - CAMS

In answer to your questions, the plant receives about 17 Ml/d of mainly domestic origin. We have some trade waste users, primarily comercial laundries, a dairy and a tannery.
I am currently trying to get the foam tested to determine the primary constituents. I shall then follow it up with trade waste testing of those compounds.
Foaming (biological and surfactant) is often a problem at the plant, typically during winter. This particulary episode however has now existed for 3 months and is considered excessive. The surfactant foaming occurred at the same time we had biological foaming, although now the biological foam has eased, while the surfactant foam remains.
The reason for dosing anti-foam before the filters is because the foam interfers with the ultrasonic level indicators on top of the filters. The same happens in the filtered water tank. Also, it foams at the creek discharge point which looks unsightly. Of course, we want to use as few chemicals as possible, so we are looking for a preventitive approach, rather than just a cure.
Is it more likely that the surfactant is formed during the process rather than coming from trade waste?
I have read through the other foam subjects, however these deal mainly with biological foams. We can easily manage biological foams, primarily with sprays over the clarifier distribution channel.
Can you give some advice as to what I should be testing for in the foam?

Answer

in relation to tests to conduct please read http://appliedcolloidssurfactants.blogspot.com/2004/03/analytical-testin g-whitish-foam-at.html.
For a detailed analysis you will have to contact a specialized lab.

I would suggest to test the incomming waste streams, preferentially at the discharge points of the laundries, the diary and the tannery, if possible. First determine whether the excessive foaming properties are related to the incomming streams or appear after the processing.
Ask the companies about any substantial change made during and before the last three month.
If synthetic surfactants are causing the trouble more extensive aerobic treatment and/or optimized coagulation/flocculation should be effective, if cutting the influent concentration at source is not possible. The latter should be your preferred option.

In principle ultrasonic detection should be also able to detect the foam - liquid interface. You should consider this or eventually a more mechanistic detection principle, a floating detector or so.

I feel this topic would be ideal for a case story. Please keep us informed.


Comment by Ciaran Gillen - Applied Environmental Biotechnology

The surfactants from the laundries are likely to be predominantly nonionics and cationics with some amphoterics. Pick one of these classes of surfactants and check the different trade streams. I would be very surprised if the surfactant foaming you are seeing is formed in the process. The main cause is likely to be the influent and most likely the laundries.


Comment

surfactants from laundries are of the anionic/nonionic type. However, these should be readily biodegradable. Which means that they loose their surfactant properties, also their foaming properties. But I am not sure if at your location surfactants with poor biodegradability are still in use.
The chance that surfactants with poor degradability coming from the tannery or that proteins from the dairy are causing the foaming seems to be higher.

Comment by Grrun
You might want to consider bubbler or pressure level sensors which would be insensitive to foam levels.

Comment by Geoff
grrun is right about the change of sensors. We found foam deflected the signals and we could never get them to work. Pressure sensors solved the problem.

Feedback by Hilary
I have received the anayltical results of the foam and it contains nonylphenol ethoxylate. Is it likely that this has caused the foaming?
We have sent letters out to our trade waste customers requesting copies of the MSDSs of process and cleaning products they use that may enter the sewer. I shall keep you posted!


Comment
Dear Hilary,

thanks for the information.
Than indeed the surfactant from tannery and/or laundry should be to blame. However, who knows if the diary is using a nonylphenol based cleaner. There might be some synergistic effects with other components from tannery or diary, which enhance the foaming effect of the nonionic surfactant with low degradability.
First you will have to continue the detective work about the source or sources. Maybe you can convince them to use an alternative surfactant with higher degradability. You should tell them that these products do a lot of harm to the environment and health because these have hormonlike effects.
If you are not able to achieve a replacement of these nonionic surfactants you might try addition of a cationic polyelectrolyte and carbon adsorption in front of sand filtration.

Hope you could stop them discharching considerable amounts of nonylphenol ethoxylates into the environment.
Comment by SciTrav


Hi Hilary
A couple of interesting references on nonylphenol ethoxylate ...
http://216.31.193.171/asp/1_search_pisubstancehelp.asp?id=1034〈= _e
http://www.europarl.org.uk/news/infocus/nonylphenol2003.htm
http://www.epa.gov/ORD/NRMRL/EDC/projects/edc_ww.htm


Comment by Aquaticonsult

Hilary - we ran into this issue for one of the main clothes soap/detergent manufacturers - the foaming was actually blowing manhole covers off when they discharged down to the municipal wastewater plant. We found we could add a specific formulation of catalyti enzyme - which allowed the foam to "break" within 2-5 seconds.

Not familiar with the particular surfactant you discussed, but the surfactants we tested would foam with simple pump agitation - regardless of where aeration was present or not (pump was totally submerged, as was suction and discharge - foaming occurred regardless) - you might contact Dick Kersey at ECP International and discuss it with him - he worked directly with the detergent manufacturer (US - 800-322-1648, email of orendatech@earthlink.net).
DAve/Aquatic Technologies.

Comment by Ciaran Gillen
Hi Hilary,
The nonyl phenol ethoxylates are being phased out in Europe due to major concerns about their estrogenic effects on aquatic life. However it is possible to use bioaugmantation to biodegrade these surfactants. If you need any information on this please do not hesitate to contact me.
cgillen@biofuture.ie


Comment
Dear Ciaran Gillen, Dear Hilary,

so good news about bioaugmentation.
What is with the nonylphenol and short glycolether chain degradation products, which normally accumulate and are at least as harmful as the original nonylphenol ethoxylates? Foaming will disappear - but are you sure that the nonylphenol residue is broken up?
Still the best option is to replace the surfactant at source.

Hilary - Problem fixed

The information from the tannery showed that they use up to 100 kg/day of a polyoxyethylene nonly phenyl ether detergent. They also stated that they have changed products as of the 10th of August.

When I spoke to one of the plant operators and aksed how the foam was going, they said it had cleared up about 3 weeks ago...around the 10th August!

So, we have identified the cause, which has coincidentally been resolved. I now appreciate the importance of a multi-pronged approach to investigations! And knowing the right questions to ask in order to get the right information.