First question I have is what is the root cause for the foaming. Have you done an microscopic analysis. What does your slide look like? Lots of filaments? Filamentous organisms are probably the cause to the foaming. Do you have a lot of Fats, Oils and Grease? Low nutrients and high loading due to industry can also cause foaming as well as septicity. Settleability: A young sludge condition (low MLSS) may cause the supernatant to have a gray to green cloudy appearance. Just a few points. I suggest a microscopic look and check your MLSS. Come back with some of your results.
I agree with comments above. A separate observation is that the foaming causes loss of biomass over the sides of the reactor. This becomes a self-perpetuating problem and the biomass concentration will stay low. Absence of biomass is often a cause of foaming. In this case, I would recommend reducing the aeration (if possible). We do alot of work with winery effluent and this type of effluent foams excessively. (try blowing through a straw into a glass of wine to see what I mean). To contain the foaming, the aeration tanks have concrete roofs. This holds the biomass. (http://hwt.co.za/wine-cellar-effluent/treatment-process/foaming/)