Abstract
Using milk casein and several kinds of surfactants as chemical agents, removal of suspended solids by coagulation and foam separation with dispersed air was examined. Casein functioned both as a collector and a frother, and coagulating flocs were almost perfectly recovered in foam generated from the liquid. Although oleic acid of anionic surfactant functioned as a collector, the removal efficiency of suspended solids was lower than that of casein. In contrast, cationic, amphoteric, and nonionic surfactants did not function act as collectors. It was clarified that casein had a much greater capacity for producing the hydrophobic interface of flocs than the surfactants used. However, all of the surfactants could also be utilized as frothers for recovering the hydrophobic flocs with casein.
For municipal wastewater treatment, a very high removal efficiency was obtained with a small amount of casein (3mg·l-1), because detergent contained in the wastewater functioned as a frother. In this method using casein, detergent is one of the object substances in wastewater. It is utilized as a foaming agent and is removed with foam.
