Foam separation, as well as removal of cellular particulates (froth flotation), is probably limited in this system by incomplete foam removal. Although a trough is provided to carry off the collapsed foam, the stability of the foam product results in maintenance of a large foam head which only infrequently falls into the waste trough. To improve harvesting, foam is removed manually each day, and the wall of the column above the liquid level is wiped clean. For future applications, a tower designed to facilitate rapid and complete collection of the foamate is recommended. Because of the relatively long foam residence time in the upper portion of this column, considerable adsorption onto the wall occurs. The open top also permits loss through the escape of aerosols. Attempts to quantify protein and dissolved organic carbon (DOC) in the foamate, therefore, have not been as successful as in samples taken from the liquid phase of the system.
To determine efficiency of foam separation in this system, samples were analyzed for protein and DOC (Table 1). Protein concentrations were determined by the Folin procedure (LowRy et al., 1951). For DOC determinations, samples were prepared according to SIEBURTH (in press), and were analyzed using an infrared carbon analyzer .