ABC Wastewater Collection Level 2 Practice Exam 2026 – All-in-One Resource to Master Your Certification!

Dissolved air flotation (DAF) thickeners utilize pressurization to introduce air into the wastewater treatment process, which helps in separating solid waste from the liquid. The most common pressurization mode for DAF systems is the recycle pressurization method.

In recycle pressurization, a portion of the treated effluent is recirculated and pressurized, allowing for a controlled introduction of air into the recycled flow. This method ensures that the air dissolves effectively into the water, which is crucial for the flotation process. When the pressurized water exits the pressurization system, the drop in pressure causes the dissolved air to form tiny bubbles that attach to solids, enabling them to rise to the surface and form a sludge blanket that can be effectively removed.

This method is favored because it optimizes the air-to-water ratio and maximizes the efficiency of the flotation process, leading to better solid removal and overall performance of the thickening operation. In contrast, other pressurization methods, such as gravity or low pressurization, do not provide the same level of control or effective air dissolution required for optimal operation of DAF thickeners.

Therefore, the recycle pressurization method is recognized as the standard choice in