Compare DAF and sedimentation for solid-liquid separation – understand when to use each technology.

Overview

Dissolved Air Flotation (DAF)

Uses dissolved air to float suspended particles to the surface for removal.

Sedimentation

Uses gravity to settle suspended particles to the bottom for removal.

Comparison Table

Factor	DAF	Sedimentation
Particle size effective	10-1000 micron	50+ micron
Particle density	Can be lower than water	Must be higher than water
Space requirement	50-70% smaller	Larger footprint
Capital cost	Higher	Lower
Operating cost	Higher (air compression)	Lower (gravity only)
Start-up time	Fast (15-30 min)	Slow (hours)
Temperature sensitivity	Minimal	Affected by cold water
Oil/Grease removal	Excellent	Poor

When to Use DAF

• Low density particles (oils, greases)
• Fine particles that won’t settle
• Cold water conditions
• Limited space availability
• High flow rates
• Algae removal

When to Use Sedimentation

• Large particles
• High density particles
• Budget constraints
• Simple operations preferred
• Sludge thickening

DAF Process Details

• Inlet pressure: 4-6 bar
• Air saturation: 95-98%
• Bubble size: 10-50 micron
• Surface loading: 3-10 m3/m2.hr
• sludge concentration: 3-6%

Sedimentation Process Details

• Overflow rate: 25-50 m/day
• Weir loading: Less than 250 m3/m.day
• Detention time: 1-3 hours
• sludge concentration: 1-3%

Combined Systems

For optimal results, some facilities use both:

• DAF for primary removal
• Sedimentation for polishing

Need help choosing? Contact us for the right separation technology.

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