NIRE-170-1-6
15
Membrane Module
Air diffuser
FIC
Filtrate water
Manifold
PIA
Lower limit alarm
Air outlet
Feed
chemical
FI
L
H
L
:OP
EN
H:CLOSE
L:CLOSE
H:OPEN
VFD or auto valve
PIA
(2) Pump suction configuration
Fig. IV-3 illustrates the general configuration for pump suction filtration.
Fig.IV-3 Schematic Flow Diagram for Pump Suction Operation
When incorporating a suction pump to facilitate water flow through the membrane, the filtrate
water flow rate should be controlled using a flow meter fitted with control output signals and a
suction pump fitted with a VFD device or an automatic control valve. In the event the
membrane tank water level reaches the lower level design set point the filtration mode
should be stopped. As with the gravity filtration mode previously discussed, should the
membrane tank water level reach the upper designed liquid level set point, the high level
controller will close the raw water inlet control valve.
Since the liquid in the tank contains a significant amount of dissolved air, some of that
dissolved air will accumulate in the filtrate pump suction line.
It would be necessary to
periodically purge the filtrate line of any accumulated air and in this context it is quite
beneficial to locate the pump at the highest point of filtrate piping.
A range of methods
can be used to remove air from the filtrate line: vacuum pump, ejector or manual water
injection. Contact Toray or refer to the engineering manual for the additional details.
Raw water
Fine screen
FIC : Flow rate indicator/Controller
LS : Level Switch
PIA : Pressure indicator/Alarm
FI : Flow indicator
LS