TORAY UF
Instruction Manual
06-G-MB2-HFUG-B2315AN-220930
35 of 35
(2) Long-term storage
First, carry out a chemical cleaning with sodium hypochlorite. Fill the module with the
chemical described in Table 8. Use filtrate quality water. Follow the instructions shown in
Table 8.
Keep the modules sealed with the aqueous chemical solution shown in Table 7 or Table 8.
If removing modules from the system, seal them and store them out of direct sunlight.
Keep the modules at 1 to 40 deg C.
Table 8. Conditions for storing membrane modules for more than seven days
Storage Period
Preservative Chemical
*8)
Concentration of the
Chemical
More than 7 days
Sodium hypochlorite
10 mg/L as Cl
2
*9)
Sodium bisulfite
1,000 mg/L
*8): Select either sodium hypochlorite or sodium bisulfite chemical solution.
*9): Be careful not to exceed the sodium hypochlorite contact upper limit shown in Table 3
.
Rinse the module thoroughly with clean water after the
chemical cleaning with sodium hypochlorite and fill the
module with sodium bisulfite solution. Toxic chlorine
gas is generated when mixing sodium hypochlorite
with sodium bisulfite without first flushing with water.
3. Replace Preservative Chemical
Check the pH value of sodium bisulfite solution as the preservative and replace the chemical
if the pH is below three (3.0). Sodium bisulfite solution with a pH of 3 to 6 is active for the
preservation. Sodium bisulfite reacts with oxygen and forms sulfuric acid which results in a
lower pH
.
