Page 500 - Water and wastewater engineering

MEMBRANE FILTRATION 12-17

Example 12-2. Determine the number of modules per rack and the number of racks to provide
uninterrupted flow for the following design conditions:

3
Q max 10,000 m /d
3
2
J 0.100 m /h · m
2
Membrane area per module 50 m
Backwash interval 60 min
Backwash time 8 min
Solution:
a. Estimate the total membrane area required.

3
10 000 m /d 2
,
4 166.667 m
,
3
.
( 0 100 m /h m )( 2 24 h/d)
b. Estimate the number of modules.
4 166 67 m 2
.
,
8333 modules
.
2
50 m /module

c. Because cleaning is by racks, estimate the number of racks that must be cleaned in a
backwash cycle.
60 min/backwash cycle
7 5 racks/b. a ackwash cycle
8 min/rack

To provide a safety factor of about 25%, provide treatment capacity in six racks.
d. Estimate the number of modules per rack.

.
8333 modules
.
13 88 or 14 modules/rack
c
6 racks
e. Design summary.
1. Provide: 6 racks 1 spare for redundancy 7 racks.
2. Check flux.

3
,
10 000 m /d 3 2
.
J 0 0992 m /dm

2
m
( 6 racks)( 14 modules/rack)( 50 m /module 24)( h/d)