Removal of algae using froth flotation.

This paper describes the removal of algae and attached water using a froth flotation method as a function of the collector type, aeration rates, the pH of the algal suspension and temperature of operation. Dispersed air flotation was used in this study to remove Scenedesmus quadricaudo. The addition of surfactants such as cetyltrimethylammonium bromide and sodium dodecylsulfate increased the aeration rates and reduced the size of air bubbles. Only cetyltrimethylammonium bromide gave high algal removal (90%) whereas sodium dodecylsulfate gave poor algal removal (16%). However, by decreasing the pH values of the algal suspension, it was possible to increase the algal removal efficiency up to 80%. Low temperature operation had an important effect on reducing the rate of algal removal but when the temperature was 20 degrees C or higher there was little change with further temperature rises. The amount of water removed with the algal phase was reduced by using a two-stage flotation process.