Bio-Burden Reduction Filtration


The 3-A Accepted Practice for Supplying Air under Pressure in Contact with Milk, Milk Products and Product Surfaces, # 604-04 recognizes the need to clean compressed air that may come in direct contact with milk, milk products [primary contamination], or surfaces that contact milk and milk products [secondary contamination]. Section D6 of the 3-A Practice and Figures 1,2, 5, and 6 at the end of the Practice refer to filters, ‘coalescing filters’ and ‘final filters’, their location, installation, performance, use, and so on.

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Air and Compressed Air Contamination

Atmospheric air contains a mass of pollutants including dust, water aerosols, hydrocarbon, and other gaseous contaminants and microorganisms. Compressed air is further contaminated by the addition of liquid oil, oil aerosols, oil vapor [if an oil-lubricated compressor is used], liquid water, water aerosols, water vapor, pipe rust, and scale as well as any extra micro-organisms that may be living, growing and multiplying in the compressed air lines. All these, usually unwanted, contaminants will arrive at the points of use of a compressed air system but can be efficiently removed by various filters depending on the level of clean compressed air required.

'Bio-Burden Reduction Filtration

To comply with the requirements of the 3-A Accepted Practice and remove the micro-organisms [or ‘bio-burden‘] from the compressed air that is in contact with milk, milk products, and product contact surfaces an air sterilizing filter [or ‘final filter’] is installed at the point(s)-of-use and preceded by and protected from gross solid and liquid damage by a compressed air microfilter [or ‘coalescing’ filter]. Together, the two filters form a ‘bio-burden reduction’ filter system and exceed the requirements of the 3-A Accepted Practice. The air-sterilizing filter will remove 100% of all molds, yeasts, pollens, spores, and so on from the compressed air and these are retained in the filter fabric where they must be regularly ‘killed’ by sterilization or sanitization.

If the compressed air is being generated by an oil-lubricated compressor then the basic ‘bio-burden reduction’ filter system [comprising the micro-filter and air sterilizing filter in series] must be augmented with the addition of a charcoal-adsorbing filter. This filter is added to the downstream side of the microfilter and before the air sterilizing filter to adsorb higher hydrocarbon vapors which would otherwise contaminate the critical air sterilizing filter and get into the milk and milk products and condense on product contact surfaces.

Filter Performance

The ‘coalescing’ microfilter will remove 99.99999% of all solid and liquid contamination down to 0.01 microns on a sustained and continuous basis for the full working life of the filter element, which will be not less than 12-months at full capacity. This remarkable filtration performance is validated. When used in series with the charcoal adsorbing filter, the final oil content of the compressed air is less than 5 parts per billion. The microfilter element should be changed as indicated by the filter vessel's differential pressure gauge. The charcoal adsorbing filter should be changed every 12-months.

The ‘final’ air-sterilizing filter is 100% efficient at removing all viable microorganisms from the compressed air [or gas] and is fully validated. The filter cartridge should be sterilized [by live, clean, steam] or sanitized by autoclaving or by dunking in sanitizing fluids such as alcohol, peroxide, or CIP solutions about every 30 days or as needed. This filter cartridge will withstand 50 sterilizing or sanitizing cycles [it is validated for 100] and so it should last for years.

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