- Handling of membranes containing a preservative solution requires appropriate protective clothing like gloves, safety glasses, etc.
- This information is not intended to be exhaustive. Please refer to the specification sheet of the membrane supplier for detailed information on process limitations and storage conditions.
In no event will MMS be liable for any damages in relation to the membrane or system.
Storage of new membranes
Most polymer membranes (e.g. flat sheet and spiral wound modules) are conditioned after manufacturing with a preservative agent (e.g. glycerol or sodium metabisulfite) to ensure storage stability. The membranes are usually also sealed in plastic bags with oxygen barrier and should only be unpacked before use. Most suppliers warranty up to 6 – 12 months of storage time for new membranes stored in their original packaging.
The following storage conditions are recommended:
- Temperature: 5 – 30 °C (preferably 5 – 15 °C), no frost!
- Not supposed to direct sunlight
Storage of used membranes
Membranes should be cleaned after production and need to be stored wet. Storage can take place either inside the system or outside in closed containers or sealed bags. It is recommended to store the membranes in a preservative solution if they are not used for more than 1-2 days.
The following preservative solutions (in food-grade quality if required) may be used (chemical stability should be verified according to the suppliers’ spec sheet):
- Sodium metabisulfite 1 %
- Citric acid 1 – 2 %
- Ethanol solution 20 – 30 %
The storage conditions should comply with the ones described in the section Storage of new membranes. The preserved membrane should be inspected regularly for microbiological growth, and a pH measurement should be conducted. The storage solution must be exchanged as the circumstances require (e.g. observation of turbidity). Sodium metabisulfite may oxidize during storage, resulting in a pH decrease. The solution must be replaced at a pH of ≤ 3 to avoid membrane damages.
Ceramic membranes as well as certain types of hollow fiber and tubular membranes can be stored dry (please refer to membrane spec sheet).
Follow the steps below to store a membrane in the system:
- Ensure system and membrane have been cleaned according to operating manual.
- Start another CIP cycle and add preservative agent instead of cleaning agent (heating is not required).
- Recirculate for 5 min. under pressure.
- Shut down the system and do not flush.
After membrane storage it is recommended to flush the system and perform a CIP before starting the next production.