Glossary

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
Activated Carbon Granulated activated carbon used to remove tastes, odor, chlorine, chloramines, and some organics from water
Anion Negatively-charged ion in a solution
Backwash Reversal of a solution’s flow through a filtration system. Often used as a cleansing mechanism in sand and dual-media filters
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
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 disinfecting agent in water purification
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
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 microSiemens/cm
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
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
Disinfection The process of killing pathogenic organisms in a water supply or distribution system by means of heat, chemicals, or UV light
Dissolved Solids The residual material remaining from a filtered source after evaporating the solution to a dry state
Endotoxin A heat-resistant pyrogen, specifically a lipopolysaccharide found in the cell walls of viable and nonviable bacteria
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
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 not let the particulates through
Fouling In crossflow filtration, the reduction of flux that is attributed to a buildup of solids on the surface of the membrane
gpd Gallons per day
Grains Per Gallon (gpg) A unit of concentration equal to 17.1 milligrams per liter (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
High-Purity Water Highly-treated water with attention to microbiological reduction or elimination; the term commonly used in the pharmaceutical industry
Housing A ported chamber with closure, which directs the flow of fluid through the filter element.
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.
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
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 icrofiltration, as disc filters in laboratories, and as pleated final filter cartridges, particularly in pharmaceutical and electronic applications
mg/L Milligrams of an element per liter of water; approximately equal to ppm
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 centimeters. Symbol is ?
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
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
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
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.
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
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)
ppm Parts per million, commonly considered equivalent to milligrams per liter (mg/L)
psi Pounds per square inch (pressure).
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 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 megohmcm
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
Scaling The buildup of precipitated salts on such surfaces as pipes, tanks and boiler condensate tubes
SDI Silt Density Index – test used to measure the level of suspended solids in feedwater for a reverse osmosis system
Suspended Solids (SS) Solid organic and inorganic particles that are held in suspension in a solution
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
Turbidity A suspension of fine particles in water that cause cloudiness and will not readily settle due to small particle size
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
USP United States Pharmacopoeia which publishes standards for the pharmaceutical industry, including those for water quality. Was established by the US Congress in 1884 to control drug makeup
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
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