One advantage of the flotation system is its high applicability as a compact facility. Recently, research for the introduction of additional high-rate dissolved air flotation (DAF) into conventional water treatment plants has been progressing in areas of remodeling water treatment plants, advanced treatment, and combined sewer overflow (CSO) treatment. For successful design and operation of high-rate DAF, laboratory experiments to verify model results and estimate standard values of major parameters by model simulation were performed in this study. With the model simulation having a population balance concept, an operational analysis of bubble-floc aggregates considering a hydraulic situation in the separation zone during high-rate DAF was conducted. Based on the model simulation results, a basic level for high-rate DAF design at a hydraulic loading rate of 30 m/h was determined. On the basis of population balance theory, it can describe the process of bubble-floc aggregate formation at a contact zone and calculate the rate of transfer into the separation zone.