MIL-HDBK-1005/9A
a) Equipment. Use a back pressure inductor in the
recycle pump inlet line to infuse air into the recycle stream.
The flow through the inductor creates a partial vacuum in a side
port drawing in atmospheric air. This system is mechanically
simpler and lower in maintenance and operating cost than a
b) Bubble Size. The air pressure used in flotation
determines the size of the air bubbles formed. Air bubbles
< 100 m in size are the most suitable for being adsorbed and
entrapped by the chemical floc and oil globules. An excessive
amount of air can destroy the fragile floc formed in the
flocculator, resulting in poor performance.
c) Recycle. Recycle of a portion of the clarified
effluent allows a larger quantity of air to be dissolved and
dilutes the feed solids concentration. Dilution reduces the
detention period necessary to achieve good separation.
3.10.6.2 Design Parameters. The principal design variables for
DAF or IAF are shown below. Most of these parameters will be
specified by the equipment manufacturer.
Design Parameter
Design Value
Pressure
40 to 60 psig (276-414
kPA)
Recycle ratio
30 to 70%
0.5 to 5 lb/ft2/h (2.0 to
Feed solids concentration
20.1 kg/m2/h)
Detention period
10-30 min.
Air-to-solids ratio
0.02:1 to 0.05:1
1.0 to 3.0 gpm/ft2(40.7
Hydraulic loading
to 122.2 L/min⋅m2)
Chemical aids
Determined by field
testing
Depth to width or
0.4:1 to 0.8:1
diameter ratio
151
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