Membrane and Desalination Technologies - TCE Moodle Website

438 J. Qin and K.A. Kekre
3.2. Description of Overall Process
3.2.1. Plant Process
The schematic diagram of the plant process is shown in Fig. 10.3. The secondary treated
effluent was transferred by a submersible pump from the outfall sump through a duplex
basket strainer (370 mm) to the feed tank. The large suspended solids in the raw feed water
were removed by the strainer to prevent membrane fibers from being blocked or abraded. The
filtrate water was then transferred to the UF unit by the UF feed pump. Alum was injected into
the suction pipe before the feed pump by a dosing pump. The UF unit further removed
suspended solids and colloidal materials from the filtrate water. The UF product was collected
in the permeate tank and then overflowed into the drain.
The UF unit could be operated in the filtration mode, backwash mode, and chemically
enhanced backwash (CEB) mode (22). In the filtration mode, the UF unit was operated in
dead-end and in-out flow at a fixed water flow rate by the use of a speed variable feed pump,
and no retentate was discharged. In the backwash mode, the clean water from the permeate
tank was transferred by the backwash pump into the shell side of the UF module, then went
out from the lumen side of the fibers, and then carried the floccules on the fiber inner surface,
finally was discharged into the drain from the retentate line. The CEB mode was similar to the
backwash mode; in addition, chemicals were dosed into the suction pipe before the backwash
pump as shown in Fig. 10.3. The cleaning chemicals used were NaOCl, NaOH, and H2SO4 to
recover flux from the biofouling and scaling.
3.2.2. Hollow Fiber Unit and Trial Runs
The plant had two S-225 FSFC UF modules with total membrane area of 70 m 2 and
capacity of 2–7 m 3 /h. The UF unit was operated in a dead-end and in-out flow mode. Newly
SUMP
STRAINER
LS
FEED
TANK
V10
AV70
LS
ALUM
FEED
PUMP
AV11
AV30 AV31
AV12
AV33
MEMBRANE UNIT
AV23
AV25
SV24 SV26
FT
21
PT
21
PT
12
FT
11
H 2 SO 4
SV13
PT
10
PT
22
PT
13
V34
BACKWASH
PUMP AV60
LS
AV50
LS
AV40
LS
NaOCl
NaOH
Fig. 10.3. Schematic diagram of the plant process (13).
SV32
AV27
LS
RETENTATE
PERMEATE
TANK
V20 V25