32
(2)
Long term storage
First carry out a chemical cleaning with sodium hypochlorite. Fill the module
with the chemical described in Table 7. Use filtrate quality water. Follow
the instructions shown in Table 7.
Keep the modules sealed with the aqueous chemical solution shown in Table
6 or Table 7. If removing modules from the system, seal them and store out
of direct sunlight. Keep the modules at 0 to 40 degree C.
Table 7 Conditions for storing membrane modules for more than seven days
Storage Period
Preservative Chemical
Concentration of the
Chemical
More than 7 days
Sodium bisulfite
1,000 mg/L
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 in the case of 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 - 6 is active for the preservation. Sodium bisulfite reacts with oxygen and
forms sulfuric acid which results in a lower pH.
