Please note that while I will strive for comprehensiveness, the field of filtration is vast and constantly evolving. This list will cover key terms, but there might always be highly specialized or niche terminology not included.
Here is a detailed, comprehensive A-Z list of terminology in the filtration industry, along with their meanings and examples:
A
* Absolute Filter Rating: The diameter of the largest spherical particle that will pass through a filter under specified test conditions. It signifies the point at which 100% of particles larger than the stated micron size are captured.
* Meaning: A measure of the smallest particle size a filter can capture with complete certainty.
* Example: An absolute filter rating of 5 microns means the filter is guaranteed to remove 100% of particles 5 microns and larger. This is crucial in applications like pharmaceutical manufacturing where sterility is paramount.
* Adsorption: A process where molecules adhere to the surface of a solid material. It’s a surface phenomenon, unlike absorption where one substance is taken up by another.
* Meaning: The adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.
* Example: Activated carbon filters use adsorption to remove odors, chlorine, and organic compounds from water or air. The contaminants stick to the highly porous surface of the carbon.
* Aeration: The process of introducing air into a liquid, often water, to remove dissolved gases or oxidize dissolved metals.
* Meaning: Contacting a fluid with air to facilitate gas exchange.
* Example: In water treatment, aeration is used to remove hydrogen sulfide (rotten egg smell) or to oxidize iron and manganese so they can be filtered out.
* Agglomeration: The process of particles sticking together to form larger masses.
* Meaning: The clumping or collection of small particles into larger, aggregated particles.
* Example: In some filtration processes, promoting agglomeration before filtration can help improve the removal efficiency of very fine particles.
* Air-to-Cloth Ratio (A/C Ratio): In dust collection, this refers to the ratio of the volume of air flowing through a filter baghouse or dust collector to the total surface area of the filter media.
* Meaning: A critical design parameter for baghouses, indicating the air velocity through the filter fabric.
* Example: A baghouse with an A/C ratio of 5:1 means 5 cubic feet per minute (CFM) of air passes through 1 square foot of filter cloth. Lower ratios generally indicate better performance and longer filter life.
* Ambient Temperature: The temperature of the surrounding environment where the filtration system operates.
* Meaning: The temperature of the air or atmosphere in the immediate vicinity.
* Example: When selecting a filter material, it’s important to consider if it can withstand the ambient temperature of the industrial facility, especially in hot processes.
* Anion Exchange: A type of ion exchange process where negatively charged ions (anions) are removed from a solution and replaced by other anions (typically hydroxide ions) from a resin.
* Meaning: The reversible exchange of anions between a solid (resin) and a liquid.
* Example: Anion exchange resins are used in deionization to remove sulfates, chlorides, and nitrates from water.
* Anti-Fouling: Properties or treatments applied to filter membranes or media to prevent the accumulation of foulants (e.g., biological growth, scale, suspended solids) on their surface, which would reduce performance.
* Meaning: Resistance to the build-up of unwanted materials on the filter surface.
* Example: Many modern reverse osmosis membranes are designed with anti-fouling characteristics to extend their operational life and reduce cleaning frequency.
* Area Filtration: A filtration method where the filter medium has a large surface area, often pleated, to increase dirt-holding capacity and extend service life.
* Meaning: Maximizing the effective filtration surface area.
* Example: Pleated cartridge filters offer significantly more area filtration than a simple cylindrical filter of the same outer dimensions, allowing them to capture more contaminants.
* Asymmetry (Membrane): Refers to a membrane structure where the pore size and morphology vary across its cross-section, typically having a dense, selective layer on one side and a more porous support structure beneath.
* Meaning: Non-uniformity in pore structure or density across the membrane thickness.
* Example: Most ultrafiltration and reverse osmosis membranes are asymmetric, with a very thin, dense skin layer responsible for separation, supported by a much thicker, more open substructure.
B
* Backwash (Backflushing): A cleaning process for filters where the flow of fluid is reversed through the filter media to dislodge accumulated particles and flush them away.
* Meaning: Reversing the flow through a filter to clean the media.
* Example: Sand filters in water treatment plants are routinely backwashed to remove trapped sediment and restore their filtration efficiency.
* Bag Filter: A type of industrial filter that uses a fabric bag (made of various materials like polypropylene, polyester, nylon) as the filter media to capture solid particles from liquids or gases.
* Meaning: A versatile filter system utilizing a disposable or reusable bag element.
* Example: Bag filters are commonly used in paint production to remove undissolved pigments, in chemical processing, and for bulk filtration in various industries.
* Basket Strainer: A device with a perforated or mesh-lined basket installed in a pipeline to physically remove large solid particles from a flowing fluid.
* Meaning: A coarse filter designed to protect downstream equipment from large debris.
* Example: A basket strainer is installed upstream of a pump to prevent large debris like rust, scale, or rags from damaging the pump’s impeller.
* Bed Depth (Filter Bed Depth): In granular media filters (like sand filters), this refers to the thickness of the filter media layer through which the fluid passes.
* Meaning: The vertical height of the filter material.
* Example: A deeper filter bed depth in a sand filter typically provides better particle removal efficiency due to increased contact time and more filtration layers.
* Beta Ratio (β Ratio): A measure of a filter’s efficiency at a specific micron rating. It’s the ratio of the number of particles of a given size upstream of the filter to the number of particles of the same size downstream. A higher beta ratio indicates higher efficiency.
* Meaning: A common metric for evaluating the efficiency of a filter, particularly hydraulic and lubricating oil filters.
* Example: A filter with a Beta ratio (βx) of 200 at 10 microns means that for every 200 particles 10 microns or larger entering the filter, only 1 particle of that size or larger will pass through, indicating 99.5% efficiency. (Efficiency = (Beta – 1)/Beta * 100%).
* Biofouling: The undesirable accumulation of microorganisms (bacteria, algae, fungi) and their extracellular polymeric substances (EPS) on filter membranes or media surfaces, leading to reduced performance.
* Meaning: Fouling caused by biological growth.
* Example: Biofouling is a major challenge in membrane filtration processes for water treatment, often requiring chemical cleaning or pre-treatment.
* Bleed-Off (Blowdown): The periodic or continuous discharge of a portion of the circulating water or liquid from a system (e.g., cooling towers, boilers) to remove accumulated dissolved solids and prevent scaling or fouling, often followed by fresh water makeup.
* Meaning: Purging a portion of system fluid to control contaminant concentration.
* Example: In a cooling tower, blowdown is necessary to prevent the concentration of dissolved solids, which can lead to scale formation on heat exchangers and reduce filtration effectiveness.
* Blind Spot (Filter): An area within a filter element or system where flow is stagnant or significantly reduced, leading to inefficient filtration or potential accumulation of contaminants.
* Meaning: A dead zone in the filter where effective filtration does not occur.
* Example: Poorly designed filter housings can create blind spots where contaminants settle instead of being captured by the media.
* Breather Filter: A filter designed to remove contaminants (dust, moisture) from air entering a reservoir or tank as fluid levels change.
* Meaning: A filter that allows air to enter and exit a sealed system while preventing contamination.
* Example: A breather filter on a hydraulic reservoir ensures that the air drawn in as the fluid level drops is clean, preventing contamination of the hydraulic fluid.
* Bypass Valve: A valve designed to divert fluid flow around a filter element if the pressure drop across the filter becomes too high (indicating clogging) or if the element is removed for maintenance.
* Meaning: A safety mechanism to ensure continuous flow even if the filter is blocked.
* Example: In a hydraulic system, a bypass valve on the oil filter will open if the filter clogs, allowing unfiltered oil to reach critical components rather than starving them of lubrication.
C
* Cake (Filter Cake): The layer of accumulated solid particles that forms on the surface of a filter medium during filtration, often acting as a secondary filter medium itself.
* Meaning: The solid material deposited on the filter surface.
* Example: In a plate-and-frame filter press, the filter cake is the valuable product (or waste) that is removed once the filtration cycle is complete.
* Capillary Action: The ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. Relevant in porous filter media.
* Meaning: The movement of liquid through small pores or channels.
* Example: Capillary action plays a role in how liquid wicks through some depth filter media.
* Cartridge Filter: A cylindrical filter element, typically disposable, designed to fit inside a housing and remove particles from a fluid stream. They can be made of various materials and designs (e.g., pleated, string wound, melt blown).
* Meaning: A self-contained filter unit, often replaceable.
* Example: Cartridge filters are widely used in water purification systems (e.g., under-sink filters), chemical processing, and pharmaceutical applications for their precise filtration capabilities.
* Cation Exchange: A type of ion exchange process where positively charged ions (cations) are removed from a solution and replaced by other cations (typically hydrogen ions) from a resin.
* Meaning: The reversible exchange of cations between a solid (resin) and a liquid.
* Example: Cation exchange resins are used in water softening to remove “hardness” ions like calcium and magnesium, replacing them with sodium ions.
* Centrifugal Separator: A device that uses centrifugal force to separate particles of different densities from a fluid, often used as a pre-filter.
* Meaning: A mechanical device for separating components based on density difference and rotational motion.
* Example: Hydrocyclones (a type of centrifugal separator) are used to remove sand and silt from water before it enters finer filtration systems.
* Channeling: In a filter bed or media, the formation of preferred pathways or “channels” where fluid flows preferentially, bypassing effective filtration areas.
* Meaning: Uneven flow distribution through the filter media, leading to inefficient filtration.
* Example: If a granular media filter is not properly backwashed, channeling can occur, resulting in unfiltered water passing through the system.
* Cleanroom Filters: High-efficiency filters (often HEPA or ULPA) designed for use in controlled environments where strict limits on airborne particulate matter are required.
* Meaning: Filters for environments requiring extremely low levels of airborne contamination.
* Example: Cleanroom filters are essential in semiconductor manufacturing, pharmaceutical sterile filling, and aerospace industries.
* Coalescing Filter: A filter designed to separate two immiscible liquids (e.g., oil and water) or to remove liquid aerosols (fine droplets) from a gas stream. It causes small droplets to combine into larger ones that can then be drained.
* Meaning: A filter that causes small liquid droplets to combine into larger, more easily removable droplets.
* Example: Coalescing filters are commonly used in compressed air systems to remove oil and water aerosols, protecting pneumatic equipment.
* Colloids: Very small particles (typically between 1 nanometer and 1 micrometer) that are dispersed evenly throughout a fluid and do not settle out easily.
* Meaning: Stable dispersions of finely divided particles in a continuous medium.
* Example: Clay particles in water, proteins in milk, and some dyes are examples of colloids that require advanced filtration methods like ultrafiltration for removal.
* Concentrate (Reject): In membrane filtration (e.g., RO, UF), the portion of the feed stream that contains the concentrated impurities or rejected substances that did not pass through the membrane.
* Meaning: The stream enriched in rejected contaminants.
* Example: In a reverse osmosis system, the concentrate stream, also known as the reject or brine, contains the salts and impurities removed from the feed water.
* Cross-Flow Filtration (Tangential Flow Filtration): A filtration method where the feed fluid flows tangentially across the surface of the membrane or filter medium, sweeping away accumulated particles and minimizing filter cake build-up.
* Meaning: A filtration mode where the fluid flows parallel to the filter surface, not perpendicular.
* Example: Cross-flow filtration is widely used in membrane separation for processing biological solutions, clarifying juices, and wastewater treatment, as it reduces fouling and allows for continuous operation.
* Cryogenic Filtration: Filtration performed at extremely low temperatures, often for gases that liquefy at such temperatures or to remove impurities that solidify.
* Meaning: Filtration carried out at very low (cryogenic) temperatures.
* Example: Cryogenic filtration is used in the production of industrial gases like liquid oxygen or nitrogen to remove trace impurities.
* Cut-Off (Molecular Weight Cut-Off – MWCO): For ultrafiltration membranes, it refers to the approximate molecular weight above which 90% of the solutes are retained by the membrane.
* Meaning: A characteristic of ultrafiltration membranes indicating the size of molecules they are designed to reject.
* Example: An ultrafiltration membrane with a 10,000 Dalton MWCO will retain most molecules with a molecular weight greater than 10,000 Daltons.
D
* Deionization (DI): A process that removes dissolved ionic impurities from water using ion exchange resins.
* Meaning: The removal of all ionized salts and minerals from water.
* Example: DI water is used in laboratories, electronics manufacturing, and pharmaceutical production where extremely pure water is required.
* Depth Filter: A filter medium that traps particles throughout its entire thickness, rather than just on the surface. They typically have a progressively finer structure from the inlet to the outlet side.
* Meaning: A filter that captures contaminants within the matrix of the media.
* Example: String-wound and melt-blown cartridge filters are common examples of depth filters, effective for removing a wide range of particle sizes and holding large amounts of dirt.
* Desalination: The process of removing salt and other minerals from saline water to produce fresh water.
* Meaning: The process of making potable water from seawater or brackish water.
* Example: Reverse osmosis is the most common membrane technology used for large-scale desalination plants.
* Differential Pressure (Pressure Drop): The difference in pressure measured across a filter element, between the inlet (upstream) and outlet (downstream) sides. An increasing differential pressure indicates filter clogging.
* Meaning: The pressure loss experienced by the fluid as it passes through the filter.
* Example: Operators monitor the differential pressure gauge on a filter housing; when it reaches a predetermined maximum, it indicates that the filter is clogged and needs to be cleaned or replaced.
* Diffusion (Filter): In air filtration, particularly for very fine particles (sub-micron), diffusion is a primary mechanism where particles collide with gas molecules and deviate from streamlines, increasing their chance of hitting and sticking to filter fibers.
* Meaning: The random movement of small particles due to collisions with gas molecules.
* Example: HEPA filters effectively capture very small particles (e.g., viruses) largely through the diffusion mechanism.
* Dispersant: A chemical additive used to prevent the settling or agglomeration of particles in a liquid suspension.
* Meaning: A substance that promotes the uniform dispersion of fine particles in a liquid.
* Example: Dispersants are sometimes added to slurries before filtration to keep particles suspended and prevent premature clogging of the filter media.
* Dissolved Solids (TDS – Total Dissolved Solids): The total amount of all inorganic and organic substances that are dissolved in a liquid, often expressed in parts per million (ppm) or milligrams per liter (mg/L).
* Meaning: The concentration of all dissolved chemical species in a fluid.
* Example: Reverse osmosis membranes are highly effective at removing dissolved solids from water, significantly reducing its TDS level.
* Downstream: The side of the filter system where the filtered fluid exits, or any equipment located after the filter.
* Meaning: The effluent or filtered side of a system.
* Example: Protecting the downstream pump from particulate damage is a primary reason for installing a filter.
* Drainage Layer: A porous layer within a filter media or membrane module that provides a pathway for the filtered fluid (permeate) to exit the system.
* Meaning: A layer designed to facilitate the collection and removal of the filtrate.
* Example: In spiral wound membrane elements, a permeate drainage layer allows the filtered water to flow to the central collection tube.
* Dust Collector: An air pollution control device that removes particulate matter from air or gas streams in industrial processes.
* Meaning: An equipment system designed to capture and remove airborne dust and other particulates.
* Example: A dust collector is used in a woodworking shop to capture sawdust generated by saws and sanders, improving air quality and safety.
E
* Efficiency (Filtration Efficiency): A measure of how well a filter removes contaminants, typically expressed as a percentage of particles removed at a specific micron rating.
* Meaning: The percentage of contaminants removed by a filter.
* Example: A filter with 99% efficiency at 1 micron means it removes 99 out of every 100 particles that are 1 micron or larger.
* Effluent: The fluid that has passed through the filter and is now considered “filtered” or “treated.” Also known as permeate or filtrate.
* Meaning: The outflow or discharge from a filter or treatment process.
* Example: The effluent from the water treatment plant’s sand filters is then typically disinfected before distribution.
* Electro-deionization (EDI): A water purification technology that combines ion exchange resins with ion-selective membranes and an electric current to continuously deionize water without the need for chemical regeneration.
* Meaning: An electrically driven deionization process.
* Example: EDI systems are used to produce ultra-pure water for demanding applications like power generation (boiler feed water) and semiconductor manufacturing.
* Electrophoresis: The movement of charged particles in a fluid or gel under the influence of an electric field. Can be used in some advanced separation techniques.
* Meaning: The migration of charged particles in an electric field.
* Example: While not a primary filtration method, electrophoresis principles can be involved in some specialized membrane fouling phenomena or advanced separation processes.
* Electrostatic Precipitator (ESP): An air pollution control device that uses electrostatic force to remove fine particles from a flowing gas stream. Particles are charged, then collected on oppositely charged plates.
* Meaning: A device that removes particles from air or gas using an electric field.
* Example: ESPs are widely used in power plants to remove fly ash from flue gases before they are released into the atmosphere.
* Element (Filter Element): The removable part of a filter assembly that contains the actual filter media.
* Meaning: The replaceable component that performs the filtration.
* Example: When a cartridge filter clogs, the old filter element is removed and replaced with a new one.
* Emulsion: A mixture of two immiscible liquids where one is dispersed in the other in the form of very fine droplets.
* Meaning: A stable dispersion of one liquid in another, typically oil in water or water in oil.
* Example: Oily wastewater often forms emulsions that are difficult to filter and may require specialized coalescing filters or membrane separation.
* Entrainment: The process by which one substance is carried along or trapped within another, often undesirable, especially when referring to liquids carried in gas streams.
* Meaning: The carrying over of liquid droplets or solid particles by a gas or liquid flow.
* Example: Mist eliminators are used to prevent liquid entrainment in gas pipelines, which can lead to corrosion or damage to downstream equipment.
F
* Feed Water/Fluid: The unfiltered liquid or gas that enters the filtration system.
* Meaning: The influent stream requiring filtration.
* Example: The river water drawn into the treatment plant is the feed water for the entire purification process.
* Felt (Filter Felt): A non-woven fabric, often synthetic, used as a filter medium, particularly in bag filters. It provides depth filtration.
* Meaning: A dense, fibrous material used for filtration.
* Example: Polyester felt filter bags are commonly used for filtering paints and resins due to their good chemical resistance and depth filtration capabilities.
* Fiber (Filter Fiber): The individual filaments from which filter media, especially non-woven or woven fabrics, are constructed.
* Meaning: The basic building block of many filter media.
* Example: The diameter and arrangement of synthetic fibers in a melt-blown cartridge determine its micron rating and dirt-holding capacity.
* Filter Aid: A finely divided, porous material (e.g., diatomaceous earth, perlite, cellulose) added to a fluid before filtration to improve filtration rates, clarity, and prevent blinding of the filter medium by forming a more porous cake.
* Meaning: A material added to a liquid to improve filtration performance.
* Example: Diatomaceous earth is often used as a filter aid in brewing to clarify beer and remove yeast and other suspended solids.
* Filter Cartridge: (See Cartridge Filter)
* Filter Cloth: A woven or non-woven fabric used as a filter medium, particularly in filter presses and bag filters.
* Meaning: A permeable fabric used for separating solids from liquids.
* Example: A polypropylene filter cloth is chosen for a filter press handling acidic slurries due to its chemical resistance.
* Filter Media/Medium: The permeable material (e.g., paper, cloth, membrane, sand, activated carbon) through which a fluid passes and on which the suspended particles are retained.
* Meaning: The actual material that performs the separation.
* Example: Sand and gravel are common filter media in rapid sand filters for water treatment.
* Filter Press: A batch filtration device that uses pressure to force liquid through filter cloths, capturing solids in chambers to form a filter cake.
* Meaning: A mechanical device used for dewatering slurries by pressing them through filter cloths.
* Example: Filter presses are widely used in chemical plants, wastewater treatment, and mining for solid-liquid separation and dewatering.
* Filter Housing: The outer container or vessel that holds the filter element or media and directs the fluid flow through it.
* Meaning: The enclosure that contains the filter medium.
* Example: A stainless steel filter housing is typically used for applications requiring high purity or corrosive fluids.
* Filtrate: The fluid that has passed through the filter media, similar to effluent or permeate.
* Meaning: The clean fluid that has been separated from the suspended particles.
* Example: The filtrate from the coffee maker is the brewed coffee, while the grounds remain on the filter.
* Filtration Rate: The volume of fluid processed per unit of filter area per unit of time (e.g., gallons per minute per square foot, L/hr/m²).
* Meaning: The speed at which fluid passes through a filter.
* Example: A higher filtration rate means the system can process more fluid in a given time, but can also lead to faster clogging if the filter is overloaded.
* Flocculation: The process of aggregating very fine suspended particles into larger, more easily settleable or filterable “flocs” by adding chemical coagulants or polymers.
* Meaning: The formation of larger aggregates from smaller particles.
* Example: In wastewater treatment, flocculation is often used as a pre-treatment step to enhance the removal of suspended solids before sedimentation or filtration.
* Flow Rate: The volume of fluid passing through a system or filter per unit of time (e.g., GPM, LPM).
* Meaning: The quantity of fluid flowing per unit of time.
* Example: The filter system was designed to handle a maximum flow rate of 100 GPM.
* Fouling: The undesirable accumulation of material (e.g., biological growth, scale, suspended solids, organic matter) on the surface or within the pores of a filter membrane or media, leading to reduced performance and increased pressure drop.
* Meaning: The reduction of filter performance due to accumulation of unwanted substances.
* Example: Membrane fouling is a major operational challenge in reverse osmosis systems, requiring regular cleaning cycles.
* Full Flow Filtration: A filtration system where 100% of the fluid flow passes through the filter element.
* Meaning: All of the fluid stream is directed through the filter.
* Example: Engine oil filters typically use full flow filtration to ensure all circulating oil is cleaned before returning to the engine.
G
* Gas Filter: A filter specifically designed to remove particulates, aerosols, or specific gaseous contaminants from a gas stream.
* Meaning: A filter used for purifying gas.
* Example: Gas filters are critical in semiconductor manufacturing to ensure ultra-pure process gases are delivered to the sensitive equipment.
* Gasket (Filter Gasket): A mechanical seal that fills the space between two or more mating surfaces, generally to prevent leakage from or into the filter housing or element.
* Meaning: A sealing component used to prevent fluid bypass.
* Example: A properly installed gasket is essential for preventing unfiltered fluid from bypassing the filter cartridge.
* Gauge Pressure: The pressure measured relative to the ambient atmospheric pressure.
* Meaning: Pressure relative to the surrounding air pressure.
* Example: A pressure gauge on a filter housing measures the gauge pressure, indicating the pressure within the system.
* Gel Layer: In membrane filtration, a dense layer of concentrated solutes or colloidal particles that can accumulate on the membrane surface, increasing resistance to permeate flow.
* Meaning: A dynamic layer of concentrated solutes or particles that forms on a membrane surface.
* Example: The formation of a gel layer can lead to significant flux decline in ultrafiltration processes.
* Granular Activated Carbon (GAC): A form of activated carbon, typically in granular form, used extensively for adsorption of organic compounds, chlorine, and odors from water and air.
* Meaning: Activated carbon in granular form, used as a filter medium.
* Example: GAC filters are common in municipal water treatment plants to remove taste and odor-causing compounds.
* Gravity Filter: A filtration system where the fluid flows through the filter media under the influence of gravity alone, without external pressure.
* Meaning: A filter that relies solely on gravity for fluid movement.
* Example: Slow sand filters used in some water treatment systems operate as gravity filters.
H
* HEPA Filter (High-Efficiency Particulate Air Filter): A type of air filter that traps at least 99.97% of airborne particles 0.3 micrometers (µm) in diameter.
* Meaning: A high-efficiency air filter meeting specific capture standards.
* Example: HEPA filters are mandatory in operating rooms and cleanrooms to maintain stringent air purity standards.
* Housing (Filter Housing): (See Filter Housing)
* Hydraulic Filter: A filter designed to remove particulate contamination from hydraulic fluid, protecting hydraulic pumps, valves, and cylinders from wear and damage.
* Meaning: A filter for hydraulic oil systems.
* Example: Regular replacement of hydraulic filters is crucial for the longevity and reliable operation of heavy machinery and industrial presses.
* Hydrophilic: Having a strong affinity for water; “water-loving.” Hydrophilic filter membranes or media are easily wetted by water.
* Meaning: Easily wetted by water.
* Example: Most membranes used for aqueous filtration are inherently hydrophilic or are modified to be so, allowing water to pass through easily.
* Hydrophobic: Lacking affinity for water; “water-fearing.” Hydrophobic filter membranes or media repel water but can allow gases to pass.
* Meaning: Repels water.
* Example: Hydrophobic filters are used as vent filters to allow air to pass into a sterile tank while preventing liquid entry or to filter air in humid environments.
I
* Impaction (Inertial Impaction): A filtration mechanism where larger, heavier particles, due to their inertia, deviate from the fluid streamlines and collide with filter fibers, becoming trapped.
* Meaning: Particle capture due to inertia causing them to hit and stick to filter media.
* Example: This mechanism is dominant in air filters for capturing larger dust particles.
* Impurities: Unwanted substances present in a fluid that need to be removed by filtration.
* Meaning: Contaminants or unwanted components in a substance.
* Example: Common impurities in industrial water include suspended solids, dissolved minerals, organic compounds, and microorganisms.
* Influent: The fluid flowing into a filter or treatment system; synonymous with feed water/fluid.
* Meaning: The incoming flow to a filter.
* Example: The influent wastewater enters the primary sedimentation tanks before filtration.
* Interception (Direct Interception): A filtration mechanism where particles, following the fluid streamlines, come within one particle radius of a filter fiber and are captured.
* Meaning: Particle capture by directly encountering a filter fiber.
* Example: This mechanism is effective for particles slightly smaller than the filter’s pore size but still large enough to be “intercepted” by the fibers.
* Ion Exchange: A reversible chemical process where undesirable ions in a solution are exchanged for other ions that are attached to an insoluble solid matrix (resin).
* Meaning: A reversible process where ions are exchanged between a solution and an insoluble solid.
* Example: Water softeners use ion exchange resins to remove hardness ions (calcium, magnesium) and replace them with sodium ions.
J
* Jacketed Filter Housing: A filter housing designed with an outer jacket or shell through which a heating or cooling fluid can be circulated to maintain the temperature of the process fluid inside the filter.
* Meaning: A filter housing with an external shell for temperature control.
* Example: A jacketed filter housing might be used to maintain the temperature of a viscous liquid, such as chocolate or heavy oil, to ensure it flows easily through the filter.
K
* Kieselguhr: German term for Diatomaceous Earth, a common filter aid. (See Filter Aid)
L
* Laminar Flow: Fluid flow characterized by smooth, parallel layers, with no disruption between the layers. Favored in some membrane filtration applications to reduce fouling.
* Meaning: Fluid flow in smooth, ordered paths.
* Example: Designing membrane systems for laminar flow can help minimize shear stress on the membrane and reduce particle deposition.
* Leaf Filter: A type of pressure filter consisting of a series of filter leaves (frames covered with filter cloth or mesh) enclosed in a pressure vessel.
* Meaning: A pressure filter using multiple flat filter elements.
* Example: Leaf filters are used for filtering edible oils, chemicals, and pharmaceuticals, particularly when filter cake recovery is important.
* Leakage (Filter): The undesirable passage of unfiltered fluid around or through a compromised filter element or seal.
* Meaning: The escape of unfiltered fluid past the filter media or seals.
* Example: A torn filter bag or a damaged gasket can lead to filter leakage, resulting in contaminated effluent.
* Lenticular Filter: A type of depth filter constructed from multiple filter sheets (pads) stacked together and sealed, often resembling a lens.
* Meaning: A stack of disc-shaped filter pads.
* Example: Lenticular filters are commonly used in the food and beverage industry (e.g., wine, beer, spirits) for clarification and sterile filtration.
* Load (Filter Load): The amount of contaminants a filter is designed to handle or has accumulated before it needs cleaning or replacement.
* Meaning: The quantity of contaminants a filter has processed or can hold.
* Example: A filter with high dirt-holding capacity can handle a heavier contaminant load before requiring maintenance.
* Lumen (Hollow Fiber Membrane): The hollow interior channel of a hollow fiber membrane through which fluid typically flows.
* Meaning: The internal passage of a hollow fiber.
* Example: In hollow fiber membrane modules, the feed water might flow through the lumen, and the permeate collects on the outside of the fibers.
M
* Melt Blown Filter: A type of depth cartridge filter made by extruding molten polymer through fine nozzles, then rapidly cooling and collecting the resulting fibers to form a randomly bonded matrix.
* Meaning: A depth filter produced by melting and extruding polymer fibers.
* Example: Melt-blown filters are popular for water pre-filtration due to their excellent dirt-holding capacity and graded density structure.
* Membrane: A thin, selective barrier that allows certain substances to pass through while retaining others. The basis of microfiltration, ultrafiltration, nanofiltration, and reverse osmosis.
* Meaning: A selective barrier used for separation.
* Example: Polymer membranes are commonly used in reverse osmosis systems for desalination.
* Membrane Bioreactor (MBR): A wastewater treatment process that combines activated sludge biological treatment with membrane filtration to produce a high-quality effluent.
* Meaning: A wastewater treatment technology integrating biological treatment and membrane separation.
* Example: MBR systems are gaining popularity for municipal and industrial wastewater treatment due to their compact footprint and superior effluent quality.
* Membrane Fouling: (See Fouling)
* Membrane Permeate: (See Permeate)
* Microfiltration (MF): A membrane filtration process that removes suspended solids, bacteria, and large colloids, typically with pore sizes ranging from 0.1 to 10 micrometers.
* Meaning: A membrane process for removing larger suspended particles and microorganisms.
* Example: Microfiltration is used for pre-treatment before reverse osmosis, clarification of beverages, and removal of bacteria from water.
* Micron (Micrometer, µm): A unit of length equal to one-millionth of a meter (10⁻⁶ meters). Used to express particle sizes and filter pore sizes.
* Meaning: A unit of length used for measuring very small distances, especially particle and pore sizes.
* Example: A human hair is approximately 50-100 microns in diameter, while bacteria can be as small as 0.2 microns.
* Micron Rating: A nominal or absolute value indicating the smallest particle size a filter can effectively remove.
* Meaning: The specified size of particles a filter is designed to remove.
* Example: A 1-micron filter is designed to remove particles of 1 micrometer and larger.
* Mist Eliminator: A device designed to separate liquid droplets from a gas stream.
* Meaning: A device to remove fine liquid droplets from a gas.
* Example: Mist eliminators are used in chemical plants to recover valuable liquids or prevent emissions of hazardous aerosols.
* Module (Membrane Module): A packaged unit containing multiple membrane elements (e.g., hollow fibers, spiral wound, plate and frame) designed for a specific filtration application.
* Meaning: A complete, self-contained membrane filtration unit.
* Example: A single reverse osmosis system might contain several spiral-wound membrane modules connected in series.
N
* Nanofiltration (NF): A membrane filtration process that removes smaller dissolved organic molecules, multivalent ions, and some dissolved salts, typically with pore sizes in the range of 0.001 to 0.01 micrometers (1 to 10 nanometers).
* Meaning: A membrane process for removing small organic molecules and multivalent ions.
* Example: Nanofiltration is used for water softening, removal of natural organic matter (NOM), and color removal from water.
* Nominal Filter Rating: An arbitrary value assigned by the filter manufacturer, indicating the approximate size of the smallest particles that the filter can retain. It typically represents 60-98% removal efficiency at that micron size.
* Meaning: An approximate indication of particle retention capability.
* Example: A nominal 10-micron filter might remove most particles 10 microns and larger, but some may still pass through. This is less precise than an absolute rating.
* Non-Woven Media: Filter media made from fibers that are randomly arranged and bonded together, rather than woven into a regular pattern.
* Meaning: Filter material made from randomly oriented fibers.
* Example: Melt-blown and spun-bonded filter cartridges use non-woven media, providing depth filtration.
O
* Oil Filter: A filter specifically designed to remove contaminants from lubricating oils, primarily in engines and machinery.
* Meaning: A filter for engine or lubricating oil.
* Example: An automotive oil filter removes dirt, metal particles, and sludge from engine oil to prevent wear.
* Osmosis: The spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize solute concentrations on the two sides.
* Meaning: The natural movement of water across a semi-permeable membrane.
* Example: Osmosis is the natural process that reverse osmosis works against to purify water.
* Outgassing: The release of dissolved or trapped gases from a material, often undesirable in high-purity filtration applications.
* Meaning: The release of gas from a solid or liquid.
* Example: Filter materials chosen for vacuum systems or critical gas lines must have minimal outgassing properties to avoid contamination.
P
* Particle Counter: An instrument used to measure the number and size of particles in a fluid (liquid or air).
* Meaning: A device for quantifying particle contamination.
* Example: Particle counters are used to monitor the cleanliness of hydraulic fluids or air in cleanrooms.
* Particulate Matter: Fine solid or liquid particles suspended in a gas or liquid.
* Meaning: Microscopic solid or liquid particles suspended in a medium.
* Example: Dust, pollen, soot, and smoke are examples of particulate matter in air.
* Permeate: The fluid that has passed through a membrane filter; synonymous with filtrate or effluent.
* Meaning: The purified fluid that passes through a membrane.
* Example: The permeate from the reverse osmosis system is now suitable for drinking water.
* Perlite: A naturally occurring volcanic glass that is heat-treated to form lightweight, porous particles, commonly used as a filter aid.
* Meaning: A filter aid derived from volcanic rock.
* Example: Perlite is used as a filter aid in the food industry for juice clarification.
* Pleated Filter: A filter element where the filter media is folded into pleats (accordion-like folds) to increase the effective surface area within a compact volume.
* Meaning: A filter with a folded media design for increased surface area.
* Example: Pleated air filters in HVAC systems provide a larger filtration area than flat panel filters, extending their service life.
* Plug Flow: A flow pattern in which all elements of the fluid move at the same velocity, with no mixing or back-mixing. Ideal for some reactor designs but less common in most filter beds.
* Meaning: Fluid flow where there is no axial mixing.
* Example: Achieving true plug flow in a large filter bed is difficult, as some channeling or short-circuiting typically occurs.
* Pore Size: The size of the openings or channels within a filter medium that allow fluid to pass through.
* Meaning: The diameter of the holes or passages in the filter media.
* Example: The pore size of a microfiltration membrane determines the smallest particles it can retain.
* Pre-coat Filtration: A filtration method where a layer of filter aid (e.g., diatomaceous earth) is first deposited onto a support medium (like a screen or septum) before the actual filtration process begins.
* Meaning: Applying a layer of filter aid to the filter medium before filtration starts.
* Example: Swimming pool filters often use pre-coat filtration with diatomaceous earth to achieve high clarity.
* Pre-filtration: The initial stage of filtration, typically using a coarser filter, to remove larger particles and protect finer downstream filters from premature clogging.
* Meaning: A preliminary filtration step.
* Example: A 10-micron sediment filter is often used as a pre-filter before a 1-micron carbon block filter in residential water treatment.
* Pressure Filter: A filter system where the fluid is forced through the filter media under pressure, rather than relying on gravity.
* Meaning: A filtration system operating under positive pressure.
* Example: Cartridge filters and filter presses typically operate as pressure filters.
* Pressure Drop: (See Differential Pressure)
* Primary Filter: The first filter in a multi-stage filtration system, often a coarse filter designed to remove the bulk of larger contaminants.
* Meaning: The initial filter in a series.
* Example: In an HVAC system, the primary filter removes larger dust and lint, protecting the more efficient secondary and HEPA filters.
* Process Fluid: The specific liquid or gas being treated or filtered in an industrial process.
* Meaning: The fluid involved in an industrial operation.
* Example: The process fluid in a chemical plant might be a corrosive acid, requiring specific filter materials.
* Purification: The process of removing impurities or contaminants from a substance to make it clean or pure.
* Meaning: The act of making something clean or free from impurities.
* Example: Water purification involves a series of filtration, disinfection, and sometimes membrane separation steps.
R
* Regeneration (Ion Exchange): The process of restoring the capacity of an ion exchange resin by flushing it with a concentrated solution of the ions it initially exchanged.
* Meaning: Restoring the ion exchange capacity of a resin.
* Example: A water softener regenerates its resin by flushing it with a brine (salt) solution, releasing hardness ions and reloading it with sodium ions.
* Reject (Membrane Filtration): (See Concentrate)
* Retention: The ability of a filter to hold back particles or solutes. Often expressed as a percentage.
* Meaning: The capability of a filter to prevent substances from passing through.
* Example: A filter with 99% retention of particles 1 micron and larger.
* Reverse Osmosis (RO): A membrane filtration process that forces a solvent (e.g., water) from a region of high solute concentration through a semi-permeable membrane to a region of low solute concentration by applying external pressure, overcoming osmotic pressure.
* Meaning: A membrane separation process that removes dissolved ions and molecules by applying pressure.
* Example: RO systems are widely used for desalination, ultrapure water production, and municipal drinking water treatment.
* Reticulated Foam: An open-celled foam material with a three-dimensional network of interconnected pores, often used as a depth filter or pre-filter.
* Meaning: A porous, sponge-like material with interconnected pores.
* Example: Reticulated foam filters are used in air conditioning units or as pre-filters in industrial applications due to their high dirt-holding capacity.
S
* Sanitary Filter: A filter designed and constructed to meet stringent hygienic standards, often used in food, beverage, and pharmaceutical industries, featuring smooth surfaces, no dead spaces, and easy cleaning (CIP/SIP).
* Meaning: A filter designed for hygienic applications, preventing contamination and easy to clean.
* Example: Sanitary filters are essential in dairies to ensure milk purity and prevent bacterial growth.
* Screen Filter: A basic filter type that uses a woven mesh or perforated plate to remove particles larger than the screen openings.
* Meaning: A filter that uses a mesh or perforated screen as the media.
* Example: Screen filters are often used for irrigation water to remove large debris like leaves and twigs.
* Seal (Filter Seal): A component (e.g., O-ring, gasket) designed to prevent fluid bypass around or between filter elements and housing components.
* Meaning: A device used to prevent leakage or bypass of fluid.
* Example: Proper seating of the O-ring seal is critical to ensure no unfiltered fluid bypasses the cartridge filter.
* Secondary Filter: A filter positioned downstream of a primary filter, designed to remove finer particles that the primary filter might have missed.
* Meaning: A filter that follows a primary filter in a multi-stage system.
* Example: In an HVAC system, the secondary filter (e.g., MERV 13) captures finer dust particles not removed by the MERV 8 primary filter.
* Sediment Filter: A filter designed to remove physical particles or sediment (sand, rust, silt) from a fluid.
* Meaning: A filter for removing undissolved solid particles.
* Example: A sediment filter is often the first stage in a whole-house water filtration system to protect subsequent filters from clogging.
* Selectivity (Membrane): The ability of a membrane to preferentially pass certain components while rejecting others.
* Meaning: The degree to which a membrane separates different substances.
* Example: An ultrafiltration membrane might have high selectivity for proteins while allowing smaller salts to pass through.
* Separation: The general process of dividing a mixture into two or more distinct products or phases. Filtration is a form of mechanical separation.
* Meaning: The act of isolating components from a mixture.
* Example: The goal of industrial filtration is typically the separation of solids from liquids or gases.
* Septum (Filter Septum): The porous support layer onto which a filter cake or pre-coat is deposited in some filter types (e.g., diatomaceous earth filters).
* Meaning: A permeable support for a filter cake or pre-coat.
* Example: In a pressure leaf filter, the filter cloth acts as the septum.
* Short-Circuiting: The undesirable phenomenon where fluid bypasses the intended filtration path, flowing through gaps or imperfections in the filter media or seals, resulting in incomplete filtration.
* Meaning: Untreated fluid bypassing the filter media.
* Example: A poorly installed filter bag that doesn’t seal properly in its housing can lead to short-circuiting.
* Sintered Metal Filter: A rigid filter element made by fusing metal powder particles together at high temperatures without melting, creating a porous structure.
* Meaning: A durable, porous filter made from bonded metal powder.
* Example: Sintered metal filters are used for high-temperature applications, corrosive fluids, and where backwashing for cleaning is required, such as in catalyst recovery.
* Slurry: A thick suspension of solid particles in a liquid.
* Meaning: A semi-liquid mixture, typically of fine particles suspended in a liquid.
* Example: Wastewater treatment sludge is often handled as a slurry and dewatered using filter presses.
* Spun-Bonded Filter: A type of non-woven filter media where continuous filaments are spun and then bonded together (thermally or chemically) to form a fabric. Often used for depth filters.
* Meaning: A filter media made from continuous, bonded fibers.
* Example: Spun-bonded polypropylene filters are common as pre-filters in various water treatment applications.
* Sterile Filtration: Filtration designed to remove all viable microorganisms (bacteria, yeast, molds) from a fluid, typically achieving a very high level of purity.
* Meaning: Filtration to achieve complete removal of living microorganisms.
* Example: Sterile filtration is critical in pharmaceutical manufacturing for injectables and in the food and beverage industry for producing shelf-stable products without heat treatment.
* Strain (Filter Strain): To pass a fluid through a coarse filter or strainer to remove larger solid particles.
* Meaning: To remove large particles from a fluid using a coarse screen.
* Example: Sieves and basket strainers are used to strain out large debris.
* Strainer: A device typically using a perforated screen or mesh to remove coarse solids from a fluid stream. Less efficient than a filter for finer particles.
* Meaning: A coarse filtration device, primarily for larger particulates.
* Example: A Y-strainer is commonly installed in pipelines to protect pumps and control valves from large debris.
* String Wound Filter: A type of depth cartridge filter made by winding a continuous string or yarn around a central core in a precise pattern, creating a progressively tighter structure.
* Meaning: A depth filter created by winding yarn around a core.
* Example: String wound filters are widely used for general water filtration, offering good dirt-holding capacity and removal of sediment.
* Surface Filter: A filter medium where particles are primarily captured on the surface of the media, forming a filter cake.
* Meaning: A filter where particles are retained on the outer surface.
* Example: Membrane filters and screen filters primarily function as surface filters.
* Suspended Solids (TSS – Total Suspended Solids): Solid particles that are dispersed in a fluid but are not dissolved, and can be removed by filtration or settling.
* Meaning: Insoluble solid particles present in a liquid.
* Example: High levels of suspended solids in wastewater can clog filters and require extensive pre-treatment.
* System Pressure: The operating pressure of the fluid within the filtration system.
* Meaning: The working pressure of the fluid being filtered.
* Example: The filter housing must be rated for the maximum system pressure to ensure safe operation.
T
* Tackifier: An adhesive substance applied to some air filter media to improve particle capture, especially for smaller particles.
* Meaning: An adhesive coating on filter media to enhance particle retention.
* Example: Some disposable furnace filters use a tackifier to improve their efficiency in capturing fine dust.
* Tangential Flow Filtration: (See Cross-Flow Filtration)
* Tertiary Filtration: The third stage of filtration in a multi-stage system, often a very fine filter (e.g., membrane filter) designed for high purity or specific contaminant removal.
* Meaning: A high-level filtration step after primary and secondary filtration.
* Example: Tertiary filtration using activated carbon is sometimes employed after sand filtration and disinfection to remove trace organic contaminants from drinking water.
* Thin-Film Composite (TFC) Membrane: A type of membrane, particularly common in reverse osmosis, consisting of three layers: a very thin, dense selective layer (polyamide), a porous support layer, and a non-woven fabric backing.
* Meaning: A multi-layered membrane designed for high performance.
* Example: Most modern RO membranes are TFC membranes, offering high rejection rates and durability.
* Turbidity: A measure of the cloudiness or haziness of a fluid caused by suspended particles.
* Meaning: A measure of the cloudiness of a fluid due to suspended solids.
* Example: Filtration reduces the turbidity of water, making it clearer and more aesthetically pleasing.
U
* ULPA Filter (Ultra-Low Penetration Air Filter): An even higher efficiency air filter than HEPA, capable of trapping 99.999% of particles 0.12 micrometers and larger.
* Meaning: An extremely high-efficiency air filter for highly demanding cleanroom environments.
* Example: ULPA filters are used in semiconductor fabrication plants to prevent contamination of microchips.
* Ultrafiltration (UF): A membrane filtration process that removes macromolecules (proteins, polysaccharides), viruses, and colloids, typically with pore sizes ranging from 0.001 to 0.1 micrometers.
* Meaning: A membrane process for separating macromolecules and larger colloids.
* Example: Ultrafiltration is used for concentrating proteins, clarifying fruit juices, and as a pre-treatment for reverse osmosis in water purification.
* Upstream: The side of the filter system where the unfiltered fluid enters, or any equipment located before the filter.
* Meaning: The influent or dirty side of a system.
* Example: The pressure gauge located upstream of the filter indicates the inlet pressure.
V
* Vacuum Filter: A filtration device that uses a vacuum (negative pressure) on the downstream side of the filter medium to draw the fluid through and separate solids.
* Meaning: A filter that uses a vacuum to enhance filtration speed.
* Example: Rotary drum vacuum filters are commonly used for dewatering slurries in industries like mining and chemical processing.
* Viscosity: A measure of a fluid’s resistance to flow.
* Meaning: The internal friction of a fluid.
* Example: Filtering high-viscosity fluids (like heavy oils or certain paints) often requires higher pressures, heated filter housings, or specialized filter media.
* Volatile Organic Compounds (VOCs): Organic chemical compounds that have high vapor pressure at ordinary room temperature. Many VOCs are harmful and can be removed from air or water by activated carbon filtration.
* Meaning: Organic compounds that easily vaporize at room temperature.
* Example: Activated carbon filters are effective at removing VOCs like benzene, toluene, and xylene from air streams or drinking water.
W
* Washing (Filter Washing): The process of rinsing the filter cake or filter media with a clean fluid to remove residual impurities or to recover valuable product.
* Meaning: Rinsing the filter media or cake to remove contaminants or recover product.
* Example: In a pharmaceutical filter press, the filter cake might be washed with purified water to recover any remaining active pharmaceutical ingredients.
* Water Activity: A measure of the unbound, free water available in a substance, which can affect microbial growth. Relevant in some food and pharmaceutical filtration for preservation.
* Meaning: The amount of unbound water in a system.
* Example: While not directly a filtration term, controlling water activity in certain products through filtration and drying is crucial for shelf life.
* Woven Media: Filter media made from fibers that are interlaced in a regular pattern (like a fabric).
* Meaning: Filter material constructed from interweaved fibers.
* Example: Many filter cloths used in filter presses are woven media.
Y
* Y-Strainer: A type of strainer shaped like a “Y” with the filter element in the leg of the “Y,” used to remove large particles from pipelines.
* Meaning: A Y-shaped coarse filter for pipelines.
* Example: A Y-strainer is a common choice for protecting pumps in water lines due to its compact design and ease of cleaning.
Z
* Zeolite: A class of porous mineral silicates, often used as ion exchange media or adsorbents in water treatment.
* Meaning: A natural or synthetic mineral used for ion exchange and adsorption.
* Example: Zeolites can be used in some filtration systems to remove ammonia or heavy metals from water.
* Zero Liquid Discharge (ZLD): A wastewater treatment philosophy or system design where all the water is recovered and reused, and no liquid waste is discharged from the facility. This often involves advanced filtration and separation technologies.
* Meaning: A wastewater treatment goal to eliminate all liquid effluent.
* Example: Industries facing strict environmental regulations may implement ZLD systems, heavily relying on advanced membrane filtration (RO, UF) and evaporators.
* Zeta Potential: A measure of the electrical potential at the slipping plane of a particle in suspension, indicating the stability of a colloidal dispersion. It can influence filterability and flocculation.
* Meaning: An electrochemical property of particles in suspension that affects their tendency to agglomerate or repel.
* Example: Adjusting the zeta potential of particles through chemical addition can improve their removal efficiency by filtration or sedimentation.