SLUDGE AND SCUM COLLECTION AND TRANSFER EQUIPMENT

provide stiffness and rigidity to withstand the wave pumping action of the

aerator. Shroud material shall be steel or fiberglass. The use of wood

will not be permitted. All bolts and fastenings shall be of Type 316

stainless steel.

2.8.3.5

Draft Tube

Draft tube, where a part of the manufacturer's design, shall be fabricated

from 5 mm 3/16 inch minimum thickness steel plate, reinforced and stiffened

with structural steel sections, supported by legs, and anchored to the

bottom of the tank. It shall be designed to create a pump action by the

impeller on the liquid at the bottom of the tank to move the liquid to the

impeller for aeration. The clearance between the draft tube and the bottom

of the tank shall be such that activated sludge floc will not be broken. A

means of height adjustment shall be provided.

2.8.3.6

Mechanical Aerator Supports, Walkways and Rails

Supports for mechanical aerator mounting plate shall be placed on bottom of

tank or extended from structural steel beams on tank walls. Service

walkway to mechanical aerator shall be provided and shall have handrails on

each side.

2.9

SLUDGE AND SCUM COLLECTION AND TRANSFER EQUIPMENT

2.9.1

General

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NOTE: For plants below 0.66 L/s 15,000 GPD

capacity, hopper bottom only should be specified for

settling tanks. For plants above 4.38 L/s 100,000

GPD capacity, mechanical sludge collectors only

should be used in settling tanks. For plants between

0.66 L/s and 4.38 L/s 15,000 and 100,000 GPD

capacity, either hopper bottom or mechanical sludge

collector should be allowed as a Contractor's

option. However, of the various types of mechanical

sludge collectors, rotating sludge collectors appear

to be available for plants of 1.31 L/s 30,000 GPD

and above; chain-and-flight, 1.75 L/s 40,000 GPD and

above; traveling reciprocating type, 0.66 L/s 15,000

GPD and above.

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NOTE: Delete reference to mechanical sludge

collection equipment for extended aeration type below

0.66 L/s 15,000 GPD capacity.

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NOTE: Delete "(if used)" for extended aeration type

of 4.38 L/s 100,000 GPD capacity and above; for step

aeration type 3.0 L/s 67,500 GPD capacity and above;

and all complete mixing type plants.

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NOTE: Delete last sentence for extended aeration

SECTION 11375N

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