Flotation removal of algae from water

The dispersed air flotation process was utilized to remove algae (Scenedesmus quadricauda) from water. Three types of collector, cationic N-Cetyl-N-N-N-trimethylammonium bromide (CTAB), anionic sodium dodecylsulfate (SDS), and the nonionic Triton X-100 were used and compared. It was observed that ca. 10% of algae removal was achieved when SDS and Triton X-100 were used, respectively; and ca. 90% algae was removed when CTAB was used. Upon the addition of 10 mg l(-1) of chitosan, over 90% algae was removed when SDS was used as the collector. The electrostatic interactions between collector and algae surface plays a critical role in the removal. Effects of pH, ionic strength, air flow rate, and alkalinity on flotation efficiency were also investigated. (C) 1998 Elsevier Science B.V. All rights reserved.