A kinetic model for dissolved air flotation in water and wastewater treatment

A kinetic model for DAF is presented. The author's kinetic model consists of the equations for describing a process of bubble-floc collision and attachment in a mixing zone, and a rise velocity of bubble-floc agglomerates in a flotation tank. The attachment process is formulated on a population balance model with bubbles and flocs as a flocculation in a turbulent flow. The rise velocity of bubble-floc agglomerates is formulated with size of flocs and composition of flocs including the floc density function and attached bubble number. The experimental verification was carried out, using a batch flotation tested and a mini-plant with synthetic clay suspension and colored water. The results successfully verify the validity of the model. From a given condition such as floc size and attached bubble number, the rate and extent of removal by DAF can be readily assessed by the model. A single-collector collision model, often discussed in some occasions, seems to be not useful to describe the DAF process.