To increase the loading rate in a dissolved air flotation (DAF) process, the flocculation basin was removed, and new methods that use the hydraulic energy of the contact zone were devised. Although the highest treatment efficiency was shown at the conventional flocculation basin, when a certain treatment target percentage was set, the new methods proved to be effective at increasing the hydraulic loading rate and reducing design and operational costs. The DAF process usually uses a deep bubble bed depth to attain higher treatment efficiency, however, as hydraulic loading increases, the treatment efficiency tends to decrease because of the increase in downward current. To solve this problem, bubble bed compactness was introduced as a new index. Pressure could be used to control the bubble bed compactness, and the treatment efficiency increased at high compactness even though the size of the generated bubbles was relatively large.