MIL-HDBK-1005/9A
3.10.5.1 Diversion Pond. A skimming dam does not remove oil
immediately from the flow since it relies on the oil skimmers.
It is sized for a relatively small storm event to minimize the
backwater effect in the storm drainage channel. Use a separate
diversion pond to accommodate potential large oily waste spills
and more intense storm events. This prevents washout of the oil
over the skimming dam before it can be removed. See Figure 21
for details.
3.10.6
Dissolved Air Flotation (DAF) and Induced Air
Flotation (IAF). The DAF unit removes emulsified oil and
suspended solids through the use of chemical coagulants and
rising air bubbles. The coagulants cause the minute oil
droplets and solids to agglomerate into larger floc particles.
The air bubbles adhere to these particles causing the floc to
rise rapidly to the surface. The DAF unit is usually installed
above ground and will often require pumping of influent flow.
The DAF unit is divided into two sections. The influent enters
a flocculator chamber where it is mixed with coagulant
demulsifiers. The oily waste then flows into the flotation
section. This section has a skimmer on the surface to remove
the scum and an outlet to remove the settled sludge from the
bottom by gravity displacement or pumping. Refer to Figure 22
for a schematic representation of a DAF unit.
A similar system to the DAF is the IAF which will
remove emulsified oil, heavy metals and suspended solids
(agglomorates) from oilywaste water influent. This system
produce ultra-fine gas bubbles much smaller than conventional
mechanical and hydraulic flotation cells. The smaller bubbles
liberated from relatively high gas intake volumes provide large
surface area contacting potential for the agglomorates to rise
to the liquid surface. The agglomorates laden froth is radially
dispersed to the peripheral skim trough and then removed from
the vessel on an intermittent cycle. The skid mounted system is
compact in size and light weight which makes it more ideal for
some applications.
3.10.6.1 Pressurization Method. Introduce dissolved air to the
DAF or IAF by recycle and by pressurizing a portion of the
effluent using infused air. Mix recycles with flotation tank
contents.
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