Flotation

Natural flotation

Aided flotation

Induced flotation

Valid if the difference in density is naturally sufficient for separation.

Occurs when external means are used to promote the separation of particles that are naturally floatable.

It occurs when the density of particles is artificially decrease to allow particles to float. This is based on the capacity for certain solid and liquid particles to link up with gas (usually air) bubble to form « particle-gas » with a density lower than the liquid.

Flotation process

Air flow used Nl.m^-3 water

Size of bubbles

Input power per m³ treated Wh.m^-3

Theoretical retention time min

Hydraulic surface loading

mh^-1

Aided flotation (grease removal)

100-400

2-5 mm

5-10

5-15

10-30

Mechanical flotation (froth flotation)

10.000

0.2-2 mm

60-120

4-16

Dissolved air flotation (clarification)

15-50

40-70 μm

40-80

20-40 (excluding flocculation)

3-10