Dissolved Air Flotation is commonly used to remove which contaminant from wastewater?

• A. Oils and greases
• B. Bacteria
• C. Color
• D. Nutrients

Answer: (A)

Dissolved Air Flotation works by introducing micro air bubbles into the wastewater so they attach to buoyant contaminants and lift them to the surface for removal. This makes it especially effective for fats, oils, and greases, which form a floating layer or scum that can be skimmed off. Oils and greases are less dense than water, so when the bubbles cling to oil droplets, they become buoyant and rise readily, allowing efficient separation. Other contaminants like bacteria are typically tackled by filtration or disinfection, color often requires adsorption or chemical treatment, and nutrients are usually removed through biological processes or chemical precipitation—areas where flotation is not the primary mechanism.