2.8.1
Froth Spray Pump
The pump shall be an electric motor operated, self-contained, submersible
pump of a design acceptable for the required service. Pump capacity shall
be such that not less than 0.1 L per second 1-1/2 gpm will be supplied to
each froth spray nozzle when operating at the design head loss and pressure
requirements. The pump shall be mounted in the sludge settling tank with
the suction no less than 150 mm 6 inches below the water surface but not so
deep that the pump will pick up settled solids. An intake screen shall be
provided around the pump suction. Screen openings shall be no larger than
the pump nozzle opening. Motor shall be watertight and shall be in
accordance with NEMA MG 1. Required controls, including a magnetic starter
with start and stop buttons and a circuit breaker with reset button in
conformance with NEMA ICS 1shall be provided, all enclosed in a NEMA 250,
Type 4 enclosure.
2.8.2
The froth spray header shall be at least 25 mm 1-inch diameter galvanized
steel or PVC pipe and shall be mounted above the water surface along the
tank wall opposite the air diffusers. The header shall be connected to the
froth spray pump through a gate valve and appropriate piping. Provide a
hose bib in the sludge settling zone and arranged such that the entire
froth spray pump flow can be directed through the hose bib by closing the
header gate valve.
2.8.3
Froth Spray Nozzles
Froth spray nozzles shall be constructed of bronze, stainless steel, or
plastic. Spray pattern may be either flat or conical and shall have
sufficient force at a flow rate of 0.1 L per second 1-1/2 gpm per nozzle to
effectively break down accumulated froth. Nozzles shall be mounted equally
spaced along the header to provide a slightly overlapping spray pattern at
the water surface.
2.9
GAS CHLORINATION SYSTEM
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NOTE: For small wastewater treatment plants of
75,000 to 150,000 L per day (20,000 to 40,000 gpd)
that do not require flow proportional chlorination,
tablet chlorinator offers a safe and effective means
of chlorination. Delete inapplicable chlorination
system (GAS CHLORINATION SYSTEM or CALCIUM
HYPOCHLORITE CHLORINATION SYSTEM).
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A system shall be provided for the disinfection of the treatment plant
effluent using chlorine gas. The system shall include a gas chlorinator,
booster pump diffusers, pipe, valves, and controls. The system shall
automatically regulate the chlorine feed rate in proportion to the
wastewater flow.
2.9.1
Gas Chlorinator
The chlorinator shall be of the flow proportioning continuous solution feed
type. The gas system shall operate under vacuum. The chlorinator shall
include a vacuum regulator, flow meter, flow proportioning valve,
proportioner, and ejector.
SECTION 11390
Page 21
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