Which wastewater characteristics affect grease and scum removal efficiency?

• A. Dissolved oxygen and pH
• B. Dissolved solids and temperature
• C. Temperature and floatable solids
• D. Temperature and pH

Answer: (B)

Grease and scum removal depends on how readily fats and oil float to the surface and can be skimmed off. Temperature plays a key role because warmer water lowers the viscosity of fats, helping grease coalesce and rise to the surface more quickly. It can also slightly reduce surface tension, aiding the flotation process.

Dissolved solids affect the density and surface conditions of the wastewater. As solids dissolve, the water becomes denser, which changes the buoyancy forces acting on oil and grease, influencing how well floatable material separates and rises. They can also alter the tendency of emulsions to break, impacting how cleanly grease and scum separate from the liquid.

Dissolved oxygen and pH mostly influence biological treatment and chemical reactions rather than the physical flotation process, so they’re not the primary drivers of grease and scum removal efficiency. Temperature and dissolved solids together capture the main factors controlling flotation performance.