station) should be considered to provide uniform
flow and avoid surges through the plant. Decision
should be based on undesirability of surge effects
on the plant vs. economics of the recirculation
system.
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Raw sewage recirculation box shall be fabricated of 6 mm 1/4 inch steel
plate and shall have suitable sized connections for incoming raw sewage
line, plant influent line, and recirculation line. Box shall have a fixed
weir and an adjustable weir or other suitable means of flow regulation so
that a portion of the incoming raw sewage may be recirculated. A removable
or hinged cover shall be provided. Joints inside walls, bottom, and
partitions shall be welded continuously inside and out. After welding,
weld spatter and extreme roughness shall be removed. Inlet shall be not
less than 200 mm 8 inch size.
2.14.5
Plant Influent Flow Division Box
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NOTE: Delete this paragraph for extended aeration
type 0.66 L/s 15,000 GPD and below and for all step
aeration type and complete mixing type plants and
extended aeration type when complete mixing type
plants and extended aeration type when eventual
conversion to step aeration type is contemplated.
**************************************************************************
When two or more aeration tanks are provided, a plant influent flow
division box shall be provided. The box shall be fabricated of 6 mm 1/4
inch steel plate and shall have suitably sized connections for incoming raw
sewage line and influent lines to each aeration tank. The box for dividing
flow between two tanks shall have a hinged divider plate that will permit
adjustment of from zero to 100 percent to either outlet. Divider plate
shall have locking nut and handle. The box shall have a hinged cover with
provisions for padlocking. All inside walls, bottom, and partitions shall
be welded continuously inside and out. After welding, all weld spatter and
extreme roughness shall be removed. Flow division boxes for more than two
tanks shall be as specified herein, except that method of flow division
shall be as recommended by the manufacturer of the plant.
2.14.6
Aeration Tank Influent Distribution Channel
**************************************************************************
NOTE: Delete this paragraph for extended aeration
type except when eventual conversion to step
aeration type is contemplated.
**************************************************************************
**************************************************************************
NOTE: Use first optional wording in fifth sentence
for step aeration type and second optional wording
for complete missing type.
**************************************************************************
The aeration tank influent distribution channel shall be continuously
welded to the side of the tank wall. The bottom of the channel shall be at
the same elevation as the liquid surface of the aeration tank. The inlet
to the channel shall be at one point and not less than 200 mm 8 inches in
SECTION 11375N
Page 78
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