Glossary

Glossary of Filtration Terms – A

ABSOLUTE:
In filtration is used in reference to the micron rating of cartridge or disc filters, indicating that all particles larger than a specified size will be trapped within or on the filter and will not pass through.

ABSOLUTE PRESSURE:
Pressure above an absolute vacuum. One atmosphere (14.7 p.s.i.) greater than gauge pressure. Symbolized as psia when the pressure is expressed in psi units.

ABSORB:
The process by which a liquid penetrates the solid structure of the absorbent’s fibers or particles, which then swell in size to accommodate the liquid.

ABSORPTION:
The taking in, incorporation or reception of gases, liquids, light or heat. (phys/chem.) Penetration of one substance into the inner structure of another. Occurs between a gas or vapor and a liquid. The process of movement of a drug from the site of application into the extracellular compartment of the body.

ACFM:
Stands for Actual Cubic Feet per Minute. In air and gas streams the ACFM is the actual flow. When corrected for pressure and temperature, ACFM can be correlated to SCFM (Standard Cubic Feet per Minute).

ACTIVATED CARBON/CARBON:
Activated carbon media from charcoal (which is activated by heating charcoal to 800-900ºC forming a material of high adsorptive capacity for many gases, vapors, organics, etc.) has a large internal surface area of approx. 1,000 m2/g. Commonly used in domestic/residential water filtration, the pharmaceutical industry to remove organic contaminants and in automotive applications as cabin air filters. They can be used either as an additive in granular form which is then filtered out or as a filter media in a filtration device itself. In water filtration applications, activated carbon chemically bonds with and removes certain contaminants when water is filtered through it. Carbon filters can vary in effectiveness as many remove chlorine and improve taste and odor, while others remove a considerable range of contaminants including asbestos, lead, mercury and volatile organic compounds (VOC’s). Generally, activated carbon media will not effectively remove common inorganic contaminants such as arsenic, fluoride, hexavalent chromium, nitrate and perchlorate from water. Carbon filter media usually comes in either carbon block or granulated activated carbon form. See also Carbon Block & Granulated Activated Carbon.

ACTIVATED CLAY:
An adsorbent clay that removes color, odor, free fatty acids and more from oils and tallows.

ADMIX:
Medium that is added directly into a batch tank of pre-coat to create a permeable filter cake. Usually used in place of body feed.

ADSORB:
The act of selectively attracting and holding a gas, vapor, liquid, chemical or colloid onto the surface of a solid.

ADSORPTION:
Retention of gas, liquid or solid on a surface due to positive interaction (attraction) between the surface and the molecules of the adsorbed material.

ALKALINITY:
Capacity for neutralizing an acid, usually due to presence of bicarbonate or carbonate ions. Hydroxide, borate, silicate, or phosphate ions may contribute to alkalinity in treated water.

ANION:
In water treatment, a negatively-charged ion in a solution.

ANISOTROPIC (ASYMMETRIC) MEMBRANE:
A membrane in which the pore size and structure are not the same from one side of the membrane to the other. Such membranes are usually considered “directional” because of the difference in flow characteristics depending on which side of the membrane faces the feed stream.

ASSAY:
Analytical procedure to determine purity or concentration of a specific substance in a mixture.

ASME CODE:
Used in relation to filter vessels. ASME (American Society of Mechanical Engineers), Boiler and Pressure Vessels.

AUTOCLAVE(ING):
A chamber for sterilizing with saturated steam filters or equipment by using constant high temperature and pressure (121ºC, 15 psi). One method of (“terminal”) sterilization using saturated steam.