ARMY TM 10-4610-309-14
MARINE CORPS TM 10802A-14/1
TACTICAL WATER PURIFICATION SYSTEM (TWPS)
0003 00
DESCRIPTION AND THEORY OF OPERATION
THEORY OF OPERATION
MICROFILTRATION SYSTEM BACKWASH OPERATION
Valve sequencing for backwash is handled by the PLC (Programmable Logic Controller). The PLC
program fixes the frequency at 15-minutes intervals. If the RO Feed Tank level has not reached 100%,
the tank will fill to 100% before backwash begins. THE OPERATOR MUST MANUALLY START THE
FIRST BACKWASH SEQUENCE.
The backwash operation is run automatically through the following stages (see Figure 8; also refer to AIR
1. Drain fibers: 15 psig air pushes water out of the MF fibers to the RO feed tank
a. Valves V-111, V-112, and V-201 close. Valves V-113 and V-202 open.
b. Air System Solenoid Valve XV-902 opens to allow low-pressure air through Check Valve
V-912 and into the upper filtrate outlet channel of the MF system. This low-pressure air
purges the filtrate out of the MF fibers to the RO feed tank.
2. Pressurize fibers: 100 psig air pressurizes the inside of the MF fibers
a. XV-902 and V-202 close.
b. With all valves now closed, including MF Upper Filtrate Valve V-201, Solenoid Valve XV-
901 opens allowing 100 psig air through Check Valve V-912 to pressurize the filtrate side
(inside) of the MF fibers.
3. Blow-back: the MF shell outlet valves are opened to allow the100 psig air in the MF fibers to blow
suddenly through the fibers to the MF shell
The Shell Backwash Upper and Shell Lower Outlet Valves V-401 and V-402 open quickly to
provide a sudden release of pressurized air. This rapid expansion of air through the fiber
pores blows the dirt layer from the outer surfaces of the fibers.
4. Scrub: air and feed water flushes dirt out of the MF shell
With the backwash air still on, Main Feed Valve V-111 de-energizes open. This allows feed
water to flush the dirt out of the MF shell, through the Backwash Upper Outlet Valve V-401
and out the TWPS waste outlet.
5. Sweep (or shell sweep): feed water only flushes dirt out of the MF shell
Backwash Air Valve XV-901 closes and the feed water continues to sweep the dirt out of the
MF shell.
6. Fill fibers: feed water flows into the MF shell and into the fibers
a. Normal flow conditions are reset.
b. Upper and Lower Feed Valves V-112 and V-113, Upper Filtrate Valve V-201, and valve
V-111 are all de-energized open.
c. Upper and Lower Backwash Valves V-401 and V-402 de-energize closed and the feed
water is pushed into the fiber walls and into the fiber cores.
7. Rewet 1: air is used to force water into the fibers, then the air pressure is released
a. The Feed Valve V-111 and the Main Filtrate Valve V-202 close.
b. The Upper Backwash Valve V-401 opens to exhaust pressure from the shell.
c. The Upper Backwash Valve closes and the Backwash Air Valve XV-901 opens to
pressurize the water in the fibers through Check Valve V-912.
d. XV-901 closes, the Main Filtrate Valve V-202 opens and, after a momentary delay, the
Upper Backwash Valve V-401 opens to blow off the air pressure. This step is noted by
the sound of air and water discharge into the RO feed tank.
8. Rewet 2
The Rewet 1 stage is repeated.
9. Return to normal
The MF filtration system returns to normal operation.
0003 00-9
