12
HELPFUL INFORMATION!
The effectiveness of this flushing protocol will depend on the
composition and volume of chemicals in the module, and minimum acceptable levels in effluent
at the end of the flush. The user must evaluate and validate the effectiveness of the process
with respect to time, temperature and other operating conditions.
u
Procedure E — Determine Cadence ILC Module Normalized Water
Permeability (NWP)
If a new or previously used and stored Cadence ILC module is used, the user will need to
measure the permeability of the module before use. Later, after using and cleaning the module,
the NWP of the module should be measured again. By comparing the NWP before and after
use, the user can determine the effectiveness of the cleaning method and also determine when
the module reaches the end of its service life.
Follow these steps to measure the module’s NWP:
1. Connect the feed line to a supply of purified water.
2. Fully open the feed and permeate 2 lines. Close retentate and permeate 1 lines.
3. Direct the permeate line to drain. If applicable, quickly open and close the retentate valve
a few times to expel any trapped air.
4. Adjust the feed pump and increase the pump speed to deliver a feed pressure value of
1 barg (15 psig) and measure/record the corresponding permeate flow rate.
5. Record the temperature of the permeate stream.
6. Stop the feed pump.
Normalize the permeate flux to 20 °C following these steps:
1. Using the permeate flow rate measurements from step #4 above, calculate the permeate flux
in units of L/m
2
/hr (LMH).
2. Using temperature correction factors (Table 2), normalize the permeate flux to 20 °C
(Equation 1).
Equation 1
Permeate flux normalized to 20 °C
3. Using the feed, retentate, and permeate 1 pressures obtained while measuring Cadence ILC
module permeability, calculate the apparent transmembrane pressure (Equation 2).
Note: Permeate 2 is open to atmosphere. For simplicity, the feed and the retentate pressures
are assumed equivalent in the dead-end method. This approximation requires a minimum
system setup with two pressure sensors on feed and permeate 1 lines.
Equation 2
Transmembrane pressure (TMP) calculation
4. Determine the apparent NWP dividing the permeate water flux at 20 °C by the
transmembrane pressure. The NWP is expressed in units of LMH/barg or LMH/psig units.
Flux at 20 °C = Permeate Flux
x
TCF
20 °C
TMP =
(
P
Feed
+ P
Retentate
)
–
(
P
Permeate 1
+ P
Permeate 2
)
2
2
