How to Store Lenticular Modules Between Uses
Lenticular filtration is a key component to almost all beverage production. In this article, we’ll focus on wine filtration and how to properly store your lenticular modules between uses to ensure the highest quality end-result.
Why Store Modules?
Some of the things we love about lenticular modules is that they are reusable and storable between uses. This means you can use them over and over again without the media warping until they are full of solids or when a regeneration procedure doesn’t bring the differential pressure back down. The Seitz Supradisc II® Lenticular Filters by Pall are some of our favorite media as beyond being storable, they are also back flushable and hot water and steam sanitize-able.
The ability to safely and securely store the media between uses - even if it is a whole year before you reuse them - greatly contributes to the economics of total throughput. They are easily stored in a liquid solution and shouldn’t be allowed to dry out as this will cause turbulence during filtration and premature fouling or bypass.
Where to store modules
While storage inside the housing is the most common, it is also acceptable to store modules in a suitable container with a lid where they can be weighed down to keep them fully submerged in the storage solution. For storage in a solution for longer than two days, we recommend removing the silicone gaskets or O-rings on the modules, otherwise, they will stretch, become brittle and break up into little pieces. A brew fermentation bucket that is not tapered is suitable for the 12” modules whereas food-grade plastic trash cans or Rubbermaid totes with lids are suitable for the 16” modules.
OPTIONS FOR STORAGE SOLUTIONS
Whatever storage solution you choose, make sure that you regularly inspect the solution to make sure that your modules are properly submerged, that the gaskets have been removed, and that your solution is still sanitary.
Inexpensive Ethanol* (Neutral vodka)
Cartridges can be stored in 40-135 proof ethanol solutions. Do not store cartridges in solutions greater than 135 proof, or the cartridge and storage container can prematurely age and crack. This storage solution is good for months to years as long as the proof doesn’t drop below 40 degrees/20% alcohol. If the ethanol solution drops below 20% alcohol, spoilage organisms can start to grow inside the module. We see a poor distribution of the alcohol, within the depth of a 16” module, unless the ethanol is circulated first which requires impractical amounts of ethanol. Therefore, we only recommend this method for 12” modules.
When choosing this method, be aware that your module should be purged with gas before storage to ensure that little to no dilution of the alcohol takes place. Remember to bring the backpressure up to 3 - 5 psi when purging to force the gas into all the pores to get most of the liquid out.
Acids* (Citric and Tartaric Acids)
Acceptable acids to store media in include citric and tartaric acid but for the long term, it must be used in combination with potassium metabisulfite (KMBS) to keep spoilage organisms from metabolizing these bio-essential acids over time. This method is commonly used in the wine industry and modules are stored this way in the long term. Periodic additions of SO2 must be maintained to keep the modules from spoiling.
*Please note: when storing modules in liquid, be aware that your module should be purged with gas before storage to ensure that little to no dilution of the alcohol takes place. Remember to bring the backpressure up to 3 - 5 psi when purging to force the gas into all the pores to get most of the liquid out. The 16” media has a large amount of surface area (5m2) and placing a wet, unpurged module in a storage solution can dilute the storage solution to the point where it won’t sufficiently protect the media over time.
Storage Under Pressure
Modules can be stored inside the lenticular housing. If opting for this choice, Pall (manufacturer) recommends steaming or hot water sanitizing them after a regeneration, then placing the drained housing under at least 1 bar (14.5 psi) and up to 1.5 bars of pressure with a food-grade gas like nitrogen. You can also use CO2 but consider that CO2 is a soluble gas and it will take longer to build up the proper pressure. If the pressure does not drop below 1 bar, the media can be stored like this for months. Please take proper safety precautions when storing under pressure as many lenticular housings are only pressure rated for liquid pressure, not gas pressure.
Solutions to Avoid
Ozone will destroy the media within minutes, as well as Iodophor, which will permanently stain the media. Caustic soda is also not recommended for a contact time of more than 6 cumulative hours, as it is difficult to remove/neutralize and it will also start to break down the cellulose structure after this amount of time.
Acid Sanitizers (Nitric or Phosphoric Acid Blends)
The manufacturers of cellulose filter media advise against using phosphoric acid or nitric acid solutions or long-term contact with oxidizing sanitizers like peracetic acid. These acids tend to break down the resin that binds the cellulose media together and that can lead to a premature breakdown of the cellulose structure, which in turn can lead to the filter media landing up in your filtered product as well as inconsistent filtrate quality.
Running these chemicals through the media just before filtration is acceptable but contact time longer than recommended is detrimental to the media. Some of them can also break down over time, change color and cause off-flavors in the media at which point bacteria can easily start to grow again.
QUICK GUIDE TO STORAGE SOLUTION OPTIONS:
|Inexpensive Ethanol (Vodka)||> Months||*Keep strength above 20%/40 proof. *Do not use denatured spirits. *Purge out water very well before submerging to avoid lowering proof < 40 degrees. This is the preferred method of storing carbon modules.|
|Nitric and Phosphoric Acid/Blends||Maximum 6 hours cumulative||Use at own risk. These acids damage the membrane structure at longer contact times.|
|Peracetic Acid at|
|≤ 3days||After this time the peroxide in the formulation will have broken down, offering little protection against spoilage.|
Storage at a higher concentration can lead to premature breakdown and/or damage of the media.
|Citric Acid 1-2% Solution||≤ 3days||After this time bacteria will target this solution. Commonly used in wineries with 50-200 ppm of added SO2 for long term storage. Periodically add more SO2 by dropping in an Inodose effervescent tablet. Care should be taken if bacteria is already present in the cartridge, then bacterial spoilage will begin within hours without added SO2.|
|Citric Acid 1-2% in combination with 50-200 ppm SO2||≥ 3 months||After this time bacteria will target this solution. Commonly used in wineries with 50-200 ppm of added SO2 for long term storage. Periodically add more SO2 by dropping in an Inodose effervescent tablet. Care should be taken if bacteria is already present in the cartridge, then bacterial spoilage will begin within hours without added SO2.|
|SO2 Solution without Acidifying 50-200 ppm or ≤1000 ppm||≥ 3 months||Not as efficient as acidifying the solution first, but still a solid choice to store your media. You can use up to 1000 ppm of SO2 which helps to bleach the media if your intention is to remove color. The lower the pH of the solution, the more effective the SO2 will be. Add more SO2 periodically (Inodose effervescent tablets) to make sure the solution stays effective.|
|Sulfuric Acid 2% Solution||6 weeks +||Recommended by the manufacturer for long term storage.|
|Caustic Soda (NaOH or KOH 1-2%)||≤ 12 hours||Difficult to neutralize, longer contact time weakens cellulose structure|
|Ozone Water/Gas||Not recommended by the manufacturer||Instant destruction of media.|
|Iodophor or other Iodine-based Sanitizers||Not recommended by the manufacturer||Permanent staining and impossible to remove.|