Emulsion breaking, flotation and skimming are techniques to remove which substance from wastewater?

• A. Solids
• B. Dissolved gases
• C. Oils
• D. Heavy metals

Answer: (C)

Oils in wastewater are targeted by emulsion breaking, flotation, and skimming. Emulsion breaking destabilizes tiny oil droplets dispersed in water, often with demulsifying chemicals, so droplets can coalesce into larger droplets. Once droplets are larger, flotation uses buoyancy—often with microbubbles from air—so the oil rises to the surface where it forms a skim. Skimming then physically removes that surface layer of oil. These techniques are not primarily for removing dissolved gases, solids, or heavy metals, which require degassing, sedimentation/filtration, or precipitation/adsorption instead.