One of my customers needed a way to remove foam scum off the surface of a liquid. He reclaims used paper. Paper scrap is reprocessed by first being introduced into a chemical solution and then made into a slurry called pulp. The pulp is passed through screens to remove bits of plastic, etc. The next process is called de-inking, to remove printing and glue. A surfactant is mixed into the pulp to loosen the inks and glues from the pulp. Then air is bubbled up to float them to the top. What this customer needed is a way to vacuum off the foam created on the surface.
I suggested using a 4″ air amplifier connected to a vacuum hood. The floating material was pushed towards the hood with a skimmer board and easily vacuumed away.