turbine unit. However, the system offers turn down
flexibility because the turbine and blower are
operated independent of each other. Sloped or
vertical walls are acceptable with this system and
the basin should have a single side water depth
within the range of 2.4 to 5 m (8 to 16 foot)
sidewater depth. In addition, turning walls are
recommended at each bend to maintain channel
velocities around the corners.
d. Jet Aeration: Jet aeration combines air flow
and pumped liquid in a vortex jet nozzle which is
discharged just above the channel floor. The jet
system consists of a recirculation pumping system
and an air blower, each feeding headers that
discharge through the jet nozzles. The typical
configuration utilizes a concrete basin with a 3.7
to 6 m (12 to 20 foot) sidewater depth, preferably
with vertical side walls. In addition, turning
walls are recommended at each bend to maintain
channel velocities around the corners. The jet
nozzles can be fixed or they can be mounted on
removable or swing headers to facilitate
maintenance. Removable and swing header systems
will require the construction of thrust blocks
located behind the nozzles to prevent any deflection
caused by the jet action.
e. Diffused Aeration/Low Speed Mixer System: In
this system, a coarse, medium or fine bubble
diffused aeration system is used in conjunction with
a submerged low speed mixing unit that supplies the
horizontal velocity. The propeller type mixer,
mounted on guide rails, is positioned immediately
upstream of the diffusers. Vertical or sloping side
walls are acceptable with basin sidewater depth
ranging between 3.7 and 6 m (12 and 20 foot). In
addition, turning walls are recommended at each bend
to maintain channel velocities around the corners.
Vertical side walls are recommended in the area of
the diffusers to maximize oxygen transfer.
Consideration should also be given to providing a
removable or swing header system to facilitate
maintenance of the diffusers.
f. System Choice: Since the configuration of the
channel will vary with the type of equipment
selected, the choice of aeration system must be
decided upon first. Each aeration system listed
above is specified herein. Only the paragraphs
applying to the aeration system selected should be
included in the specification. All paragraphs and
subparagraphs for the other aeration systems should
be deleted.
**************************************************************************
The jet aeration system shall be provided as indicated. The system shall
include air-liquid jet manifolds, [vertical propeller] [submerged
centrifugal] pumps, pneumatic backflush system, air blowers, and all
SECTION 11391
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