and suspended solids concentration between [200] [_____] and [400] [_____]
mg/L. Plant design shall conform to Sections 13080 SEISMIC PROTECTION FOR
MISCELLANEOUS EQUIPMENT and 15070A SEISMIC PROTECTION FOR MECHANICAL
EQUIPMENT [as shown on the drawings].
1.2.2.1
Contact Zone
The contact zone shall receive plant influent and bring it into contact
with stabilized activated sludge for a minimum of [30] [_____] minutes and
a maximum of [2] [_____] hours. Minimum wastewater depth shall be [3]
[_____] m [10] [_____] feet and freeboard shall be 450 mm 18 inches. A
[_____] mm -inch diameter influent opening, reinforced with a pipe flange
or steel plate and with suitable connection for the [inlet sewer] [raw
sewage pump discharge pipe] shall be provided. The influent shall enter
the tank slightly above the wastewater surface and as far as practicable
from the effluent opening. Air diffusers shall be provided in accordance
with paragraph AIR DIFFUSION EQUIPMENT. Fillets shall be provided at the
base of both long walls. A froth control spray system shall be provided in
accordance with paragraph FROTH CONTROL SYSTEM. For rectangular tank air
diffusers mounted [along one side] [in center of tank] depth to width ratio
shall be between 1.0:1.0 to 1.0:2.2 for good spiral roll mixing.
Peripheral tanks in circular plants shall utilize diffusers mounted [along
one side] [in radial pattern from inside tank wall].
1.2.2.2
Sludge-Settling Zone
The sludge-settling zone size shall be based upon a surface loading rate of
not more than [12,225] [_____] L per day per square meter [300] [_____] gpd
per square foot of water surface area at the average daily flow rate, and
not more than [20,375] [_____] L per day per square meter [500] [_____] gpd
per square foot of water surface area at the peak hourly flow rate.
Minimum water depth shall be [3] [_____] m [10] [_____] feet and freeboard
shall be 450 mm 18 inches. The tank bottom shall consist of one or more
hoppers having side slopes of not less than 1.70 vertically to l
horizontally. In lieu of the above, a flat bottom may be provided with a
mechanical sludge scraper in accordance with paragraph SLUDGE AND SCUM
RECIRCULATION EQUIPMENT. The tank influent shall be below the water
surface and shall have a stilling baffle extending at least 150 mm 6 inches
above and below the inlet opening. A scum baffle shall be provided at the
effluent opening and extending at least 75 mm 3 inches above and 300 mm 12
inches below the water surface. Air lift sludge and scum pumps shall be
provided in accordance with paragraph SLUDGE AND SCUM RECIRCULATION
EQUIPMENT.
1.2.2.3
Reaeration Zone
The reaeration zone shall be sized to provide [3 to 6] [_____] hours of
reaeration of sludge pumped from the bottom of the sludge-settling zone.
Minimum sludge depth shall be [3] [_____] m [10] [_____] feet and freeboard
shall be 450 mm 18 inches. Effluent from the reaeration zone shall
discharge to the contact zone. Air diffusers shall be provided in
accordance with paragraph AIR-DIFFUSION EQUIPMENT. Fillets shall be
provided at the base of both long walls. A froth control spray system
shall be provided in accordance with paragraph FROTH CONTROL SYSTEM.
1.2.2.4
Sludge-Holding Zone
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NOTE: Insert capacity, generally all waste sludge
SECTION 11390
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