NOTE: Retain "aeration zone" for extended aeration
type treatment plants. Retain "contact zone" and
"reaeration zone" for contact stabilization type
treatment plants.
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Air supply piping, valves, and diffusers for aeration in the [aeration
zone] [contact zone, reaeration zone] and sludge-holding zone shall be
provided.
2.6.1
Performance and Design Requirements
Aeration equipment shall be provided as required to supply a minimum of 3
cubic meters of air per minute per 100 cubic meters of tank volume 30 cubic
feet of air per minute per 1000 cubic feet of tank volume (cfm/1000 cu. ft.)
to the [aeration zone] [contact zone, reaeration zone] and the
sludge-holding zone. System design and diffuser placement shall be such
that a rolling motion is imparted to the tank contents.
2.6.2
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NOTE: Aboveground PVC and galvanized steel pipe 50
mm (2 inches) or less in diameter should be covered
by weather resistant foam thermal covering to
protect pipe from freezing.
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[Piping shall be Schedule 80 PVC.] [Piping shall be galvanized steel.]
Isolation-control valves shall be gate valves. A minimum of [three]
[_____] separate air-diffusion headers per tank shall be provided. Headers
shall be independently valved and supported and shall be capable of being
independently removed from service without the use of a crane or hoist and
without dewatering of the tank.
2.6.3
Diffusers
Diffusers shall be of the coarse bubble, fixed-nozzle type individually
attached to the headers by screwed connections, U-bolts, or stainless steel
straps and springs. Welded or other nonremovable connections are not
acceptable. Diffusers shall have an oxygen transfer efficiency of at least
6 percent and a pressure drop not greater than 3.5 kPa 0.5 psi at the
design flow rate. The diffusers shall be manufactured of plastic,
stainless steel, rubber, or other corrosion resistant material and shall be
designed to seal under no-flow conditions to prevent wastewater from
entering the piping system.
2.7
SLUDGE AND SCUM RECIRCULATION EQUIPMENT
**************************************************************************
NOTE: Retain "aeration" for extended aeration type
plants. Retain "reaeration" for contact
stabilization type plants.
**************************************************************************
Equipment shall be provided to collect sludge from the bottom of the
sludge-settling zone and pump the sludge to the [aeration] [reaeration]
zone and the sludge holding zone. Sludge collection shall be accomplished
either through the use of a hopper bottom settling tank or a flat bottom
SECTION 11390
Page 19
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