ACTIVATED-SLUDGE FOAMS - EFFECTS OF ENVIRONMENTAL VARIABLES ON ORGANISM GROWTH AND FOAM FORMATION

Actinomycetes that are implicated in foam formation in activated sludge sewage treatment plants were isolated from plants in Queensland, Australia. Foaming and surface tension determinations were carried out on mixed liquors from foaming and non-foaming plants and on pure cultures of the isolated actinomycetes which were identified as Nocardia amarae. Foam stability of mixed liquors increased with increasing temperatures and concentration of mixed liquor suspended solids. The results showed that a surfactant was released by the organisms and that the bacterial cells were responsible for stabilization of laboratory scale foams. The nitrogen source for growth did not affect the foam or surfactant production, however, the carbon source produced growth form-dependent changes to the foam but did not affect surfactant production.