ALGAE, BUBBLES, COAGULANTS, AND DISSOLVED AIR FLOTATION

This paper like Ken Ives' PhD research comments upon algae and their r emoval from drinking water. Specifically, algal properties, difficulti es in removing algae by conventional treatment, and dissolved air flot ation (DAF) as a treatment method are emphasized. The stability of alg al suspensions may be due to surface charge, hydrophilic effects, or s teric effects. Coagulation is required as a pretreatment step in DAF t o destabilize algal particles relative to the microbubbles, and thus e nsure particle-bubble attachment. The air supplied in DAF may be expre ssed fundamentally as mass, volume, and number concentrations of air b ubbles. Calculations show high bubble volume concentrations compared t o suspended particle volumes. The effectiveness of flotation is examin ed in terms of dimensionless products and compared to other particle p rocesses. DAF is compared to settling for algal separation in experime nts with DAF operating at higher overflow rates and smaller flocculati on times. DAF produced clarified waters with lower turbidities and alg al counts.