ALGAE, BUBBLES, COAGULANTS, AND DISSOLVED AIR FLOTATION

This paper like Ken Ives' PhD research comments upon algae and their removal from drinking water. Specifically, algal properties, difficulties in removing algae by conventional treatment, and dissolved air flotation (DAF) as a treatment method are emphasized. The stability of algal suspensions may be due to surface charge, hydrophilic effects, or steric effects. Coagulation is required as a pretreatment step in DAF to destabilize algal particles relative to the microbubbles, and thus ensure particle-bubble attachment. The air supplied in DAF may be expressed fundamentally as mass, volume, and number concentrations of air bubbles. Calculations show high bubble volume concentrations compared to suspended particle volumes. The effectiveness of flotation is examined in terms of dimensionless products and compared to other particle processes. DAF is compared to settling for algal separation in experiments with DAF operating at higher overflow rates and smaller flocculation times. DAF produced clarified waters with lower turbidities and algal counts.