Starter for research on Foam formation at wastewater treatment plants

Water and Wastewater.com Help Forum - The problem of Foam formation at wastewater treatm

Question of Envirotic
I Intend to start a new research work about the problem of Foam formation at wastewater treatment plants and need your help.

any link about the subject which deals with

1- material and kinds of detergent most effective
2- effect on ecology of receiving water
3- treatability at the plant
4- practical way to overcome the problem economically and ecologically
5- lab work most useful and
6- any other Ideas I missed


Answer
please be aware that the problem of foaming in wastewater treatment plants can have very different causes and is very complex. Therefore, I would strongly recommend to restrict yourself to one or two aspects or to a more defined case study.
The complexity starts with the origin of foaming. As far as I know the most common case is foaming of bulking sludge. In this case not outside detergents are responsible but filamentous organisms and exopolymers.
Beside detergents (surfactants) proteins and other biopolymers can cause foaming.

Some answers to your questions.
'most effective' -
#most common are Alkylbenzene sulfonates (household and laundry detergents) - but normally not a problem because of degradability
# most problematic - surfactants with limited degradability - alkylphenolethoxylates (can still be considered as bulk chemicals, used in industrial cleaners, paint industry, ..), specialty surfactants like fluorsurfactants (normally only in trace concentrations)

effect on ecology
# the most pronounced effect will be through the sludge they accumulate on. Primary degradation products will normally have more hydrophobic properties. Therefore, they will have an even higher tendency to adsorb (characteristic property of surfactants). Nondegraded surfactants will accumulate in the food chain. Again of major concern the alkylphenol
ethoxylates and their residues, which have hormone like properties (there is a huge amount of related literature, studies on ecological effects and accumulation in sludge).

# counter measures
naturally this depends on the actual cause, however, defoamers may be used as a first measure.
- further sorption on coal might be used, lime addition or addition of small amounts of cationic flocculant or coagulation flocculation - this especially holds if surfactants are the cause of foaming. As mentioned the tendency to adsorb is an inherent property of surfactants. Anionic surfactants (LAS, soaps) are dominate normally and degradation products of nonionic surfactants mostly have anionic carboxyl groups. I do not know if it might work, however, eventually increasing the sludge concentration should lead to a higher sorption of surfactants.

After some general review of the related literature you should decide how to proceed (focus).
It would be very interesting if you could share your progress and related problems with the help forum.

Kind regards
T. Sobisch