[_____] percent of the suspended solids and biochemical oxygen demand
(5-Day BOD) for domestic wastewater with a 5-day BOD and suspended solids
concentration between [200] [_____] and [400] [_____] mg/L at a short term
peak flow rate of [_____] L per hour gph. Plant design shall conform to
Sections 13080 SEISMIC PROTECTION FOR MISCELLANEOUS EQUIPMENT and 15070A
SEISMIC PROTECTION FOR MECHANICAL EQUIPMENT [as shown on the drawings].
1.2.1.1
Aeration Zone
The aeration zone shall be sized for a detention time of between 18 and 36
hours at the design range of flows. Minimum waste-water depth shall be [3]
[_____] m [10] [_____] feet and freeboard shall be 450 mm 18 inches.
Provide 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]. 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] the 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 diffuser mounted [along
one side] [in radial pattern from inside tank wall].
1.2.1.2
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 1
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.
1.2.1.3
Sludge-Holding Zone
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NOTE: Insert capacity, generally all waste sludge
produced in one week of operation.
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The sludge-holding zone shall have a minimum capacity of [_____] cubic
meters cubic feet. A supernatant draw-off connection shall be provided
between the sludge-holding zone and the aeration zone. The supernatant
draw-off connection shall be located above the aeration zone water level.
Air diffusers shall be provided in the sludge-holding zone in accordance
with paragraph AIR-DIFFUSION EQUIPMENT.
SECTION 11390
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