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Chemical soak cleaning (Off line cleaning)
Chemical soak cleaning is performed when recovery cleaning has not restored the trans membrane
pressure, or when sludge has adhered between membranes due to device problems or other reasons
(clogging). The whole module is immersed in a chemical solution for a long period of time to remove
fouling and restore the trans membrane pressure close to its initial value. Chemical soak cleaning
cleans more effectively than recovery cleaning.
Follow the procedure below to perform chemical soak cleaning.
Concentration of chemicals and immersion time
For NaClO (effective chlorine concentration 3,000 mg/L): 6 to 24 hours
For acid (oxalic acid or citric acid: 1 to 2 %, sulfuric acid or hydrochloric acid: 0.1 to 0.5 N): 2 to 4
hours
To clean modules
1.
Wash the module with water. Then immerse it in the washing tank.
2.
Immerse the module in the chemical soak cleaning tank under the conditions stated above
Figure 3-1.
3.
After soaking, wash the module with water again.
4.
For separate MBR systems, the modules may also be left in the membrane tank to soak,
with the sludge in the tank being replaced with chemicals.
To clean elements
1.
It is possible to extract elements from the module and immerse them in a washing tank in
order to save chemicals Figure 3-2. In this case, wash the elements with water after
extracting them from the module and then immerse them in the washing tank.
WAR NI NG
Mixing sodium hypochlorite (NaClO) and acid releases chlorine gas, which is very dangerous. Do
not mix these chemicals under any circumstances.
C AUT IO N
As the modules are very heavy, when using forklifts and cranes make sure that all apparatus is
inspected and certified, and all operators are certified.
If there is a danger of chemical leaks that may damage nearby equipment and cause
environmental pollution, be sure to take necessary measures to prevent chemicals from
splashing or spilling.
Drained water that was used for washing must either be returned to the equalization tank and
reprocessed, or disposed of as industrial waste according to relevant laws and local regulations.
Used chemicals must be disposed of as industrial waste according to relevant laws and local
regulations.
STERAPORE 5700 Series (FF) Instruction Manual
Chapter 3 Chemical Cleaning
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