MIL-HDBK-1005/7A
6.1.4
Materials of Construction . To the maximum practical
extent, use materials that are standard in ordinary engineering
practice. Special materials may be used, where economy allows,
or conditions dictate, to provide needed corrosion resistance or
other characteristics especially required in parts of the
treatment works.
6.1.5
New Devices.
New treatment devices may be used only:
a)
Where there are special needs that cannot be met
by generally accepted methods, and
b)
After testing by an impartial research or
development organization has established their usefulness and
dependability.
6.2
Screening
6.2.1
Types and Application. Bar racks with 1 1/2 - to
2-in. openings should be used to keep the large floating debris
out of intake conduits, and for all intakes to low lift pumping
stations.
6.2.1.1
Coarse Screens . For water to be filtered, use screens
with 1-in. mesh to remove the small floating debris, vegetation,
and fish that cannot be handled by bar racks.
6.2.1.2
Fine Screens . Use fine screens
as recommended in
Water Treatment Plant Design, AWWA, third
edition. The water
velocity in net screen openings should be
less than 2.0 feet per
second (ft/s) at maximum design flows and
minimum screen
submergence.
6.2.1.3
Traveling Water Screen . Use this type at freshwater
intakes following the bar racks; or at treatment plants to
remove high concentrations of coarse suspended or floating
matter.
6.2.2
Materials of Construction . In fresh water, use steel
frames for construction of screening.
6.3
Aeration. Refer to Water Treatment Plant Design,
Chapter 5, "Aeration and Stripping," AWWA, third edition;
Recommended Standards for Water Works , Part 4.5, "Aeration,"
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