Removing spent surfactants used for cleaning of aluminium from wastewater - Water and Wastewater.com Help Forum

Water and Wastewater.com Help Forum - Removing surfactants from wastewater


Question by yingiv

I am interested in finding a treatment plan for concentrated Diversey Duroclean 909, an industrial surfactant used to clean aluminum parts. The cleaning solution is currently housed in a large tank (approx 200m^3), and it occasionally gets dumped, but obviously needs to be treated before disposed. Any suggestions would be most welcome!

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Ivan


Answer

Dear Ivan,

the only information I found about the cleaner is that it is an alkaline cleaner, which is due to be checked for alkalinity during application by titration with hydrochloric acid and should be replaced when the required level of alkalinity is lost or at least after 30 days of use.
From this it is evident that it should be treated to remove alkalinity and aluminium and that it will be difficult to recycle.
Eventually by cautious neutralization aluminium might be precipitated. You might do some test in the lab. For the treatment I would suggest addition of carbon dioxide.
Further information about the cleaner composition will be necessary for additional recommendations. I hope surfactants are readily degradable as well as no recalcitrant chelatants are used. Otherwise, the cleaner should be replaced by another alternative.


Reply by yingiv

Thanks for the help everyone!

The contents of this alkaline cleaner is a variety of inorganics and organics: monosodium phosphate, sodium metasilicate, sodium tripolyphosphate, nonylphenol polyethylene glycol ether, sodium sulphate, sodium alkylaryl sulfonate, ethylene oxide

the cleaning process is essentially a dipping process. the aluminum parts are dipped into a large tank of this cleaner. currently the cleaner is being dumped into the sewage approximately once every 40 days. (as you predicted).

we are looking towards reducing the waste so that it can be reused for rinse water (in another part of the plant), but i suspect this may not economically feasible. if not, treating it to be sent to waste disposal is still an option. will an adsorber like activated carbon be realistic?


Answer

Dear Ivan,

Given the cleaner composition, I would strongly suggest to look for an alternative cleaner not containing alkylphenol polyethylene glycol ether. The problems relating to this type of nonionic surfactant were already discussed at this forum some times, mostly related to foaming (Tertiary-treatment-surfactant-foam) .
The other components do not posses dangerous properties.
(I have to correct you, the cleaner does not contain ethylene oxide - a cancer causing chemical, very reactive, forming polyethylene glycols on contact with water. Probably you mean ethylene oxide derivatives - which is a whole class of water soluble oligo- or polymers or related surfactants).
Shifting the pH to neutral, aluminumphosphates, silica gels will precipitate and oil and grease may bind to the newly generated surface or at least will be destabilized. This way using a separator you should be able to get rid of most of these contaminants.


Reply by grrun

I suspect that the pH of the cleaning solution may be high enough to act as a mild etchant to the aluminum parts and the surfactants help remove any oils that may be present on the surface of the parts. I agree with Sobisch that "cautious neutralization" would provide a good pretreatment for this type of solution. I would also suggest considering dissolved air flotation as a positive means of removing the precipitated solids and oils as well as a small portion of the surfactants.

The remaining, dissolved surfactants may be tolerated in a municipal treatment system, but you may still want to look for a cleaner with an alternate surfactant.

I also believe that any treatment of the water short of reverse osmosis would not provide a satisfactory rinse water because of the residual dissolved substances in the water which would pose problems in subsequent processing such as plating or painting.


Reply by cgillen

Dear Ivan,
It seems to me that this material would be ideal for biological pretreatment before disposal. Of course the pH would need to adjusted to near neutral and it would need to be aerated. From a quick look at the composition I suspect there will be sufficient phosphorous but a lack of nitrogen. This would need to be added - probably in the form of urea. Of course the addition of specialised microbes capable of degradation of surfactants and hydrocarbons would be required.
It should be possible to achieve a COD reduction of 60 - 70% at least and thus reduce inhibition on the sewage treatment plant.
If this is of interest please contact me directly.

Best regards,
Ciaran Gillen
cgillen@biofuture.ie