absolute: When referring to filters 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

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

absorption: The process of taking up a substance into the physical structure of a liquid or solid by physical or chemical action, but without chemical reaction.

acid rain: Rainfall below the natural pH range, caused by contact with atmospheric pollutants such as nitric and sulfuric oxides and carbon monoxide.

activated carbon: Granulated activated carbon used to remove tastes, odour, chlorine, chloramines, and some organics from water.

activated clay: An adsorbent clay that removes colour, odour, free fatty acids, etc., from oils and tallows.

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

adsorption: The process by which molecules, colloids, or particles adhere to the surfaces by physical action but without chemical reaction.

aeration: The process of adding air to a water supply for the purpose of oxidizing or mixing.

aerosols: Liquid droplets or solid particles dispersed in air or gases, of fine enough particle size (0.01 to 100 mm) to remain so dispersed for a period of time. Generally removed by coalescing filters.

agglomerate: The process of bringing together smaller divisions into a larger mass.

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

angstrom: A unit of length equalling 10-10 meters, 10-4 microns, 10-8 centimetres, and 4 x 10-9 inches. The symbol is Å.

anion: Negatively-charged ion in a solution.

antimicrobial: An additive, material, fluid or chemical that inhibits and kills the growth of micro-organisms on contact.

aquifer: Natural, underground porous formation where mineral-bearing water flows or is stored. Source of well water.

ASME code: Used in relation to filter vessels. ASME=American Society of Mechanical Engineers, Boiler and Pressure Vessels. Sections VIII and X apply to pressure vessels.

ASTM: American Society for Testing and Materials – sets the standards for laboratory and electronics water.

atmosphere: A unit measurement of pressure. The air pressure at sea level: 14.7 psi. (1 atm = 14.7 psi).

backwash: Reversal of a solution’s flow through a filtration system. Often used as a cleansing mechanism in sand and dual-media filters.

bacteria: Any of a class of microscopic single-celled organisms reproducing by fission or by spores. Characterized by round, rod-like spiral or filamentous bodies, often aggregated into colonies or mobile by means of flagella. Widely dispersed in soil, water, organic matter, and the bodies of plants and animals. Either autotrophic (self-sustaining, self-generative), saprophytic (derives nutrition from non-living organic material already present in the environment), or parasitic (deriving nutrition from another living organism). Often symbiotic in man, but sometimes pathogenic

bactericide: Agent capable of destroying bacteria.

bacteriostat: Substance that inhibits bacterial growth and metabolism but does not necessarily kill the cell.

baffle: A plate or deflector to provide flow distribution in a filter housing. Primary functions are to provide uniform flow and to prevent erosion of pre-coat or bed and setting of body feed.

bar: Designation of pressure units. 1 bar = psi ÷ 14.5.

beta rating (β) of a cartridge or element: The filtration ratio (β) is the number of particles size x μm and larger in the feed divided by the number of particles in the filtrate.

binders: In reference to cartridge filters, chemicals used to hold or “bind” short fibres together in a filter.

blind spots: Any place on a filter septum where liquid cannot flow through due to blinding or plugging.

blinding: In depth and surface filtration, a build-up of particulates on or within the filter, preventing fluid flow through the filter at normal pressures.

blowdown: In reference to boiler technology, the purge from the system of a small portion of concentrated boiler water in order to maintain the level of dissolved and suspended solids in the system below the maximum.

BOD: (Biochemical Oxygen Demand) – a measure of the amount of oxygen required for the biochemical degradation of organic material in a water sample

bottled water: Commercial products sold in containers as pure water for drinking and domestic use

bubble: The differential gas pressure that when applied to a filter element submerged in the test fluid causes the first steady emission of gas (air) from the filter element being tested. This is a means of verifying the micrometre rating of the test element.

burst: The ability of the filter medium to resist disruption by pressure applied in the direction of normal flow.

cake: The accumulation of solids on the medium, on the surface of the pre-coat or on the septum.
cake space: The volumetric space available in a filter to support the formation of a cake.

carbonate hardness: The hardness caused by carbonates and bicarbonates of calcium and magnesium in water. The amount of hardness equivalent to the alkalinity formed and deposited when water is boiled. In boilers, carbonate hardness is readily removed by blowdown

carcinogenic materials: A substance or agent producing or inciting cancer

cartridge filter: A filter device, usually disposable, filtering in the range of 0.1 micron to 100 microns, and usually 2 inches to 4 inches (51 to 102 mm) in diameter and 6 inches to 60 inches (152 to 1524 mm) in Length

cation: Positively-charged ion in a solution

caustic soda: Sodium hydroxide (NaOH), commonly known as lye. A commonly-used chemical in water treatment

cellulose: A fibrous material of vegetable origin used as a filter medium.

CFM: Cubic feet per minute

chelating agent: A molecule, usually organic, which is soluble in water and undergoes reactions with metal ions to hold them in solution. A number of naturally-occurring organic materials in water have chelating ability such as humic acid and lignin. Due to their chelating abilities, some organic materials interfere with water-softening processes

chemical solution feeder: A pump used to meter chemicals such as acid, chlorine or polyphosphate into a feedwater supply.

chloramine: A compound consisting of chlorine and ammonia gas which retains its bactericidal qualities for a longer time than does free chlorine

chlorination: The addition of small amounts of free chlorine, usually 0.2 to 2.0 ppm, to render water bacteriostatic in a water supply

chlorine: Chemical used for its qualities as a bleaching, oxidizing or dis- infecting agent in water purification

clarity: The clearness of a liquid as measured by a variety of methods.

cloth: A type of woven filter septum made from natural or synthetic yarns.

coagulant: Chemical added in water and wastewater applications to cause the formation of flocs that adsorb, entrap, or otherwise bring together sus- pended matter defined as colloidal. Compounds of iron and aluminium are generally used to form flocs to allow removal of turbidity, bacteria, colour, and other finely-divided matter from water and wastewater

coalescing: The separation of mixtures of immiscible fluids (such as oil and water) with different specific gravities. Can occur whenever two or more droplets collide and remain in contact and then become larger by passing through a coalesce. The enlarged drops then separate out of solution more rapidly.

COD: Chemical Oxygen Demand – a measure of the oxygen required to oxidize chemicals contained in a sample

colloid: A substance of very fine particle size, typically between 0.1 and 0.001 microns in diameter suspended in liquid or dispersed in gas. Typically removable only by reverse osmosis, distillation, or ultrafiltration

compaction: In crossflow filtration, the result of applied pressure compressing a reverse osmosis or ultrafiltration membrane which may result in a decline in flux.

compound: Chemical bonding or union of separate elements, ingredients, or parts

compressibility: Degree of physical change in volume when subject to pressure.

concentrate: In crossflow filtration, the portion of a feed stream which does not permeate the medium but retains and is increased in the amount of ions, organics, and suspended particles which are rejected by the medium

concentration: The amount of material contained in a unit volume of fluid; the process of increasing the dissolved material per unit volume concentration

polarization: In crossflow filtration, the formation of a more concentrated gradient of rejected material near the surface of the membrane causing either increased resistance to solvent transport, or an increase in local osmotic pressure, and possibly a change in rejection characteristics of the membrane.

condensate: Water obtained through evaporation and subsequent condensation. Normally the water resulting from condensing plant steam originally generated in a boiler. Water condensed in a water still operation is usually called distillate

conductivity: The property of a substance’s (in this case, water) ability to transmit electricity. The inverse of resistivity. Measured by a conductivity meter, and described in micro Siemens/cm

contact time: The length of time an absorbent or adsorbent is in contact with a liquid prior to being removed by the filter or to the occurrence of a chemical change.

contaminant: A source of contamination, an impurity. Any substance in water other than H2O

convoluting: The accordion pleating of filter media to obtain a large effective filtration area in a minimum volume.

crossflow membrane filtration: A separation of the components of a fluid by semipermeable membranes through the application of pressure and parallel flow to the membrane surface. Includes the processes of reverse osmosis, ultrafiltration, nanofiltration, and microfiltration

crypto: An abbreviation for Cryptosporidium, a parasite found in water; sometimes found in drinking water, municipal water systems and private wells. It is detrimental to the digestive system, causes diarrhoea, cramps and in severe cases even death.

cycle: The length of time a filter is “on-stream” before cleaning is needed. Frequently meant to include cleaning time as well.

dalton: A unit of mass 1/12 the mass of Carbon12. Named after John Dalton (1766-1844), founder of atomic theory and the first theorist since Democritus (Greek, 5th century BC) to describe matter in terms of small particles

DE: The commonly-used abbreviation for Diatomaceous Earth. Diatomaceous Earth is the fossilized skeletons of minute, prehistoric aquatic plants. Insoluble in water

decarbonation: The process of removing CO2 from water, typically using contact towers or air scrubbers.

degasification: The process of removing dissolved gasses from water, typically using vacuum or heat.

deionization (DI): Process utilizing specially-manufactured ion exchange resins which remove ionized salts from water. Can theoretically remove 100% of salts. Deionization typically does not remove organics, virus or bacteria, except through “accidental” trapping in the resin and specially- made strong base anion resins which will remove gram-negative bacteria

Delta P: A commonly-used term denoting the pressure drop across a filter.

demineralization: The process of removing minerals from water, usually through deionization, reverse osmosis, or distillation

detergent: A cleansing agent; any of numerous synthetic water-soluble or liquid-organic preparations that are chemically different from soaps but resemble them in the ability to emulsify oils and hold dirt in suspension

differential pressure: The difference in pressure between the upstream and downstream sides of a filter. It can also be the difference in pressure between two points in a system or of a component in such system.

dirt capacity: The weight of a specified artificial contaminant which must be added to the influent to produce a given differential pressure across a filter at specified conditions. Used as an indication of the relative service life.

disinfectant: A fluid or gas used to disinfect filters, demineralized (DI) water systems, pipe, pipelines, systems, vessels, etc.

disinfection: The process of killing pathogenic organisms in a water supply or distribution system by means of heat, chemicals, or UV light

disposable: Quality describing a filter which is intended to be discarded and replaced after each service cycle.

dissolved solids: The residual material remaining from a filtered source after evaporating the solution to a dry state

distillate: The product water from distillation formed by condensing vapours

distillation: The process of condensing steam from boiling water on a cool surface. Most contaminants do not vaporize and therefore do not pass to the distillate. Removes nearly 100% of all impurities

effective area: The total area of the medium exposed to flow in a filter element.

efficiency: The ability, expressed as a percent, of a filter to remove a specified artificial contaminant at a given contaminant concentration under specified test conditions.

effluent: The output stream exiting a treatment system.

electrodialysis: Dialysis that is conducted with the aid of an electromotive force applied to electrodes adjacent to both sides of the membrane

element: Any structural member in a filter on which the septum is supported. May be round, rectangular or cylindrical.

end cap: A ported or closed cover for the end of a cartridge, pipe or housing.

endotoxin: A heat-resistant pyrogen, specifically a lipopolysaccharide found in the cell walls of viable and nonviable bacteria

Endotoxin Units (EDU): Unit of measurement for pyrogen levels

EPA: Environmental Protection Agency – an organization that has set the potable water standards

evaporation: Process in which water passes from a liquid to a vapor state exhaustion: In water softening or ion exchange, the point where the resin can no longer exchange additional ions of the type the process was designed for

feed/feedwater: The input solution to a treatment/purification system, including the raw water supply prior to any treatment

filter aid: Any material that assists in the separation of solids from liquids. Usually used on difficult filter applications.

filter cake: The accumulated particles on a filter surface, usually from a slurry mixture, to enhance the filtering characteristics of a filter medium.

filter medium: The permeable material that separates particles from a fluid passing through it.

filter system: The combination of a filter and associated hardware required for the filtration process.

filtrate: Any liquid that has passed through the filter medium. Sometimes erroneously called effluent. Also known as the clarified effluent from a filter

filtration: The process by which solid particles are separated from a liquid by passing the liquid through a permeable material. Also, the physical or mechanical process of separating insoluble particulate matter from a fluid, such as air or liquid, by passing the fluid through a filter medium that will
ot let the particulates through

filtration rate: The volume of liquid that passes through a given area in a specified time. Usually expressed as gallons per square foot per minute (or hour).

floc: Coagulated groupings of formerly suspended particles which then settle by gravity.

flocculant: Chemical(s) which, when added to water, cause suspended particles to coagulate into larger groupings (flocs) which then settle by gravity

flocculation: The process of agglomerating particles into larger groupings called flocs, which then settle by gravity.

flow fatigue resistance: The ability of a filter element to resist structural failure due to flexing caused by differential pressures.

fluid compatibility: The suitability of filtration medium and seal materials for service with the fluid involved.

flux: In crossflow filtration, the unit membrane throughput, usually expressed in volume per unit time per area, such as gallons per day per ft2 or litres per hour per m2.

fouling: In crossflow filtration, the reduction of flux that is attributed to a build-up of solids on the surface of the membrane

FTU: Formazine Turbidity Units – a measure of turbidity, by a nephelometer

gauge: Thickness of steel sheet or wire diameter. The lower the gauge, the thicker the steel or larger the wire diameter. Also a device for measuring thicknesses, pressures, temperatures, etc.

Giardia cyst: A parasite found in water. Very detrimental to the digestive system, causing diarrhoea, cramps and in severe cases death.

glassing: A form for silica scaling at high temperatures, usually in high- pressure boilers or stills

gpd: Gallons per day

grains per gallon (gpg): A unit of concentration equal to 17.1 milligrams per litre (17.1 ppm)

groundwater: Water confined in permeable sand layers or cavities between rock or clay. All subsurface water

hardness: The concentration of calcium and magnesium salts in water

head: An end closure for the filter case or bowl which contains one or more ports. Also the measurement of pressure in a column of water expressed in feet of liquid depth x 0.433 = pounds per square inch.

heavy metals: Metals having a high density or specific gravity of approximately 5.0 or higher. The elemental weight is also high. A generic term used to describe contaminants such as cadmium, lead, and mercury. In low concentrations most are toxic to humans

heel: The liquid left in the filter at the end of a cycle. Also the pre-coat left on an R.V.P.F. (Rotary Vacuum Pre-coat Filter) at the end of its cycle.

High Efficiency Particulate Absolute (HEPA): A filter which removes from air 99.97% or more monodisperse dioctyl phthalate (DOP) particles having a mean particle diameter of 0.3 μm. Common use: “HEPA filter” high efficiency particulate air filter.

high-purity water: Highly-treated water with attention to microbiological

reduction or elimination; the term commonly used in the pharmaceutical

housing: A ported chamber with closure, which directs the flow of fluid through the filter element.

humic acid: A water-soluble organic compound composed of decayed vegetable matter which is leached into a water source by runoff. Present in most surface waters. Higher concentrations cause a brownish tint. Difficult to remove except by ultrafiltration or reverse osmosis

hydrocarbon: An organic compound containing only carbon and hydro- gen and often occurring in petroleum, natural gas, coal, and bitumens. Most successfully removed from water by coalescing for large volumes or by using activated carbon for small volumes.

hydrogen sulphide: A toxic gas (H2S) that is detectable by a strong “rotten egg” odour. A common by-product of anaerobic bacteria

hydrologic cycle: The natural cycle of water as it passes through the environment by evaporation, condensation, precipitation, and retention in the oceans or on land

hydrophilic: Water-accepting.

hydrophobic: Water-rejecting.

influent: The fluid entering the filter.

injection: In water treatment, the introduction of a chemical or medium into the process water for the purpose of altering its chemistry or filtering specific compounds

in-line filter: A filter assembly in which the inlet, outlet and filter element axes are in a straight line.

inside-out flow: Fluid flow through a filter element outward from and perpendicular to its longitudinal axis. This is not the normal direction of flow for most filter elements

ion: An atom or molecule which has lost or gained one or more electrons, thereby acquiring a net electric charge

ion exchange: A process in which ions are preferentially based on equilibrium, adsorbed from a solution for equivalently-charged ions attached to small solid structures called resin

LAL: Limulus Amoebocyte Lysate – a reagent used in the detection of endotoxin, the pyrogen of greatest concern to the pharmaceutical industry. The LAL reagent is made from the blood of the horseshoe crab, Limulus Polyphemus

laminar flow: A flow in which rapid random fluctuations are absent, nonturbulent

leaf: Any flat filter element that holds or supports the filter septum.

LSI: Langelier Saturation Index – an expression of a calculation that allows the prediction of calcium carbonate precipitation at a specific condition, temperature, pH, TDS, hardness, and alkalinity.

L-Type filter: A filter assembly in which the inlet and outlet ports are at 90 degrees to each other.

manifold: A set of ports that come together to form a common port.

mean filtration rating: A measurement of the average size of the pores of the filter medium.

media: The material that performs the actual separation of solids from liquids. Sometimes erroneously used to mean septum.

media migration: Release of filtration media particles into the effluent of the filter.

medium: The porous material that performs the actual process of filtration. The plural of this word is “media.”

membrane (polymeric): Highly-engineered polymer film containing controlled distribution of pores. Membranes serve as a barrier permitting the passage of materials only up to a certain size, shape, or character. Membranes are used as the separation mechanism in reverse osmosis, electrodialysis, ultrafiltration, nanofiltration, and microfiltration, as disc filters in laboratories, and as pleated final filter cartridges, particularly in pharmaceutical and electronic applications

mesh: Number of strands in a linear inch of woven filter fabric, usually wire. It is also used as a septum.

mg/L: Milligrams of an element per litre of water; approximately equal to

microfiltration (MF): Filtration designed to remove particles and bacteria in the range of 0.1 to 3 microns in diameter

micron: A metric unit of measurement equivalent to 10-6 meters,
10-4 centimetres. Symbol is μ

mixed-bed: An ion exchange tank consisting of both cation and anion resin mixed together. Provides the most complete deionization of water, up to 18.3 megohm/cm resistivity. Commonly used to polish water already treated by two-bed ion exchange tanks or reverse osmosis

module: A membrane element combined with the membrane element housing.

molecular weight (MW): The sum of the atomic weights of the constituents which make up a molecule. Often used to indicate size when referring to ultrafiltration of saccharide compounds

molecule: The smallest physical unit of a compound or chemical, composed of one or more atoms, that retains the properties of that substance

multi-pass test: The test used to determine the Beta-ratio of an element. A destructive test.

multifilament: A number of continuous fiber strands that are twisted together to form a yarn; used in weaving filter cloths.

multiple-effect evaporation: Series-operation energy economizer system where heat from the steam generated (evaporated liquid) in the first stage is used to evaporate additional liquid in the second stage (by reducing system pressure), and so on, up to 10 or more effects

nanofiltration (NF): A crossflow membrane separation process which removes particles in the 250 to 1000 molecular weight range, selected salts and most organics; sometimes referred to as a softening membrane process

nephelometer: A device used to measure mainly low-turbidity water with results expressed in Nephelometric Turbidity Units (NTU)

nominal: With regard to the micron rating of cartridge filters, refers to an approximate size particle, the vast majority of which will not pass through the filter. A small amount of particles this size or larger may pass through the filter

nominal rating: An arbitrary micrometre value indicated by various filter manufacturers.

noncarbonate hardness: Hardness caused by chlorides, sulphates, and nitrates of calcium and magnesium. Evaporation of waters containing these ions makes the water highly corrosive.

nonwoven: A filter cloth or paper that is formed of synthetic fibres that are randomly oriented in the media. Usually held together by a binder.

normal flow: The flow of the entire feedwater stream in a single direction directly through the filter medium. The flow is generally “normal,” or perpendicular, to the medium

NTU: Nephelometric Turbidity Units – the result of passing a light beam through a water sample with a nephelometer to quantify low-turbidity water. The NTU is measured by light scattering.

on-stream: Describes when a filter system is producing a filtered product while in operation.

osmosis: The spontaneous flow of water from a less concentrated solution to a more concentrated solution through a semipermeable membrane until energy equilibrium is achieved.

osmotic pressure: A measurement of the potential energy difference between solutions on either side of a semipermeable membrane. A factor in designing reverse osmosis equipment. The applied pressure must first overcome the osmotic pressure inherent in the chemical solution in order to get good purification and flux.

outside-in flow: Fluid flow is through a filter element perpendicular to and toward the axis of the element on most filters today. Exception is the coalescing element which always flows from inside to outside to remove the accumulated water from the fuel stream.

oxidation: Process by which electrons are lost to an oxidizing agent in order to increase a molecule or ion in positive valence

oxidizing filters: Filters that use a catalytic medium such as manganous oxide to oxidize iron and manganese and then filter the impurities from the water after they have been oxidized

ozonate: A device which generates ozone by passing a high-voltage current through a chamber containing air or oxygen. Used as a disinfection system.

ozone (03): An unstable, highly reactive state of the oxygen formed by passing air or oxygen through a high-voltage electric charge or strong light source. An excellent oxidizing agent and bactericide.

particle filtration (PF): Filtration rated in the range of 1 to 75 microns. Typically handled by cartridge filters.

particulate: Minute, separate pieces of matter

permeable: Allowing some material to pass through.

permeate: That portion of the feed stream which passes through a membrane, leaving behind a more concentrated stream

permeator: A hollow fine-fibre membrane element itself consisting of thousands of hollow fibres.

pH: An expression of hydrogen ion concentration; specifically, the negative logarithm of the hydrogen ion concentration. The range is from 0 to 14, with 7 as neutral, 0 to less than 7 as acidic, and 7 to 14 as alkaline (basic)

phase: A state of matter, either solid, gaseous, or liquid

polymer: A chemical compound with many repeating structural units produced by uniting many primary units called monomers.

pore: An opening in a membrane or filter matrix

porous: The ability of certain substances to pass fluids due to an open physical structure

ppb: Parts per billion, commonly considered equivalent to micrograms per litre (μg/L)

ppm: Parts per million, commonly considered equivalent to milligrams per litre (mg/L)

ppt: Parts per trillion, commonly considered equivalent to nanograms per litre (ng/L)

precipitate: An insoluble product that is in the solution or liquid mixture

precipitation: The process of producing an insoluble reaction product from a chemical reaction, usually a crystalline compound that grows in size to be settleable

precursors: Compounds such as humic acid which may lead to the creation of other compounds, such as THM

psi: Pounds per square inch (pressure).

psid: Pounds per square inch differential

psig: Pounds per square inch gauge

pyrogen: Any substance capable of producing a fever in mammals. Often an organic substance shed by bacteria during cell growth. Chemically and physically stable, pyrogens are not necessarily destroyed by conditions that kill bacteria

recirculation: a) In crossflow membrane systems, the recycling of a portion of the stream to maintain a desirable flow. b) In water system design, the continuous operation of the transfer pump to keep water flowing through the system above the use rate, to reduce the hazard of bacterial growth. A portion of the water continuously goes back to the break tank

regeneration: The displacement from the ion exchange resin of the ions removed from the process water or waste stream

rejection: In crossflow membrane systems, the process of retaining at the membrane contaminants that are larger than the membrane’s pore sizes or are repelled by an electrical charge. In a membrane system, expressed as a percent of the total presence of those contaminants

resins (ion exchange): Specially manufactured polymer beads used in the ion exchange process to remove dissolved salts from water

resistivity: The property of a substance (in this case, water) to resist the flow of electricity; the measurement of that resistance. The inverse of conductivity. Measured by a resistivity monitor and described in megohm-cm

reverse osmosis (RO): The separation of one component of a solution from another component by flowing the feed stream under pressure across a semipermeable membrane. RO concentrates ionized salts, colloids, and organics down to 150 molecular weight in the concentrate stream and provides a purified stream of water. May also be called hyperfiltration

saturation: The point at which a solution contains enough of a dissolved solid, liquid, or gas so that no more will dissolve into the solution at a given temperature and pressure

scaling: The build-up of precipitated salts on such surfaces as pipes, tanks and boiler condensate tubes

scavenger: A filter, or element in the bottom of a filter, that recovers the liquid heel that remains in the filter tank at the end of a cycle.

screen: A term commonly used for septum. Also a wire mesh screen used to screen out large-sized particles that would clog a filter cartridge. Usually installed on the suction side of a pump.

SDI: Silt Density Index – test used to measure the level of suspended solids in feedwater for a reverse osmosis system

SEMI: Semiconductor Equipment and Materials International – has set the electronics-grade purified water standards

semipermeable: In membranes, a membrane which allows a solvent such as water to pass through, while rejecting certain dissolved or colloidal substances

separator: A spiral-wound membrane element in crossflow membrane systems. Modular and replaceable

septum: A binding wall or membrane.

side seal: The longitudinal seam of the filter medium in a pleated filter element.

solutes: Matter dissolved in a solvent.

sparger: A device to introduce compressed air or gas into a liquid to agitate it or to dissolve the air or gas in this liquid. Spargers are made of porous ceramic or stainless steel in various grades (porosities) to provide a specific-sized “bubble.”

strainer: A coarse filter element (pore size over 40 μm); also a unit that screens out large particles, normally on the suction side of a pump. suspended solids

(SS): Solid organic and inorganic particles that are held in suspension in a solution

TDS: Total Dissolved Solids – See dissolved solids

THM: Trihalogenated Methane Compound – Initiated by contact between free chlorine and certain organics to form materials similar to certain organic solvents. Considered a carcinogen

TOC: Total Organic Carbon – The amount of carbon bound in organic compounds in a water sample as determined by a standard laboratory test. The CO2 is measured when a water sample is atomized in a combustion chamber

traceability: In medical and pharmaceutical device manufacturing, the stringent recordkeeping on the use and origin of component materials.

transpires: The process of a plant giving off water directly to the air

TS: Total Solids – The sum of total dissolved solids and total suspended Solids

TSS: Total Suspended Solids – The residual matter which can be removed from a solution by filtration

turbidity: A suspension of fine particles in water that cause cloudiness and will not readily settle due to small particle size

turbidity units: Measurement of the relative ability of a solution to allow a light beam to pass through it.

two-bed: A pairing of cation and anion ion exchange tanks, typically operating in series. Best used for the deionization of relatively high volumes of water. Capable of product water resistivity of up to 4 megohm/cm

ultrafiltration (UF): Separation of one component of a solution from another component by means of pressure and flow exerted on a semipermeable membrane, with membrane pore sizes ranging from 10Å to 0.2 micron. Typically rejects organics over 1000 MW while passing ions and small organics

ultrapure water: Highly-treated water of high resistivity and no organics; usually used in the semiconductor and pharmaceutical industries

ultraviolet (UV): Radiation having a wave length shorter than visible light but no longer than X-rays. Ultraviolet light with a wave length of 254 nm is used to kill bacteria and destroy ozone

unloading: The release of contaminant that was originally captured by the filter medium.

validation: In the pharmaceutical industry, the mandating of specific testing and recordkeeping procedures to ensure compliance not only with a specific quality but with a specific means to achieve that quality

vaporize: To convert a liquid into a vapor

velocity: Free air passing through a filter panel and measured in feet per minute (fpm). It is determined by the volume of air/min (ft3/m) divided by the area of the panel (ft2). It is expressed in this case as ft/min divided by feet per minute (fpm).

virus: Any of a large group of sub microscopic infective agents capable of growth and multiplication only in living cells of a host

viscosity: That property of fluids by which they offer resistance to flow. Measured in poise, kinematic viscosity, centistokes, say bolt universal seconds (SUS), seconds say bolt, degree Engler and degree Barbey, Gardner-Holt, etc.

VOC: Volatile organic compound – synthetic organic compounds which easily volatilize. Many are suspected carcinogens

voids: The openings or pores in a filter medium.

wash filter: A filter in which a larger unfiltered portion of the fluid flowing parallel to the filter element axis is utilized to continuously clean the influent surface which filters the lesser flow.

WFI: Water For Injection – high-purity water intended for use as a solvent for the preparation of parenteral (injectable) solutions. Must meet specifications as listed in the USP

WHO: World Health Organization – part of the United Nations which has set the standards for potable water

Credit: Pure Water Handbook, Osmonics