I

I

ICAP

Inductive Coupling Argon Plasma Spectroscopy

ICP

Inductive Coupling Plasma Spectroscopy

ID-50

The dose at which 50 percent of the subjects become infected.

Imhoff Cone

A clear, cone-shaped container marked with graduations.     The cone is used to measure the volume of settleable solids in a specific volume (usually one liter) of water.

Immiscible

Not capable of being mixed.     For example, oil and water are said to be immiscible.

Impeller

A rotating set of vanes in a pump designed to pump or lift water.

Impermeable

Not easily penetrated.     The property of a material or soil that does not allow, or allows only with great difficulty, the movement or passage of water.

Impounded Water

Water which is stored in an artificial man-made basin or dammed ravine by diverting flowing streams or collecting rainfall runoff, as in a reservoir.

In Situ

In place, the original location, in the natural environment.

In Vitro Studies

Studies of chemical effects conducted in tissues, cells, or subcellular extracts from an organism (i.e., not in the living organism).

In Vitrov

Literally, "in glass." A laboratory experiment performed in a test tube or other vessel.

In Vivo

Within a living organism; a laboratory experiment performed in which the substance under study is inserted into a living organism.

In Vivo Studies

Studies of chemical effects conducted in intact living organisms.

Inactivate

To make inactive or inert, esp. the alteration or destruction of a biologically active agent such as pathogenic microorganisms or antigens so as to render them harmless.

Incidence of Tumors

Percentage of animals with tumors.

Incubation Period

The time between initial contact with an infectious agent and the appearance of the first sign or symptom of disease.

Indicator

(Chemical) A chemical material or solution which can be used to show (usually by color change or depth of color) the endpoint of a chemical reaction or chemical concentration.     Examples are litmus; orthotolidine reagent.       --------------------------------------------------------------------------------    (Instrument) A device which indicates the result of a measurement.     Most indicators in the water treatment field use either a fixed scale and movable indicator (pointer), such as a pressure gauge, or a movable scale and movable indicator like those used on a circular-flow recording chart.     Also called a receiver.

Induced Infiltration

An emission spectroscopy technique for chemical analysis in which the elements that are to be measured are introduced into a high temperature (6,000 to 8,000 degrees C) argon plasma and, thereby, converted into atomic vapor.     Emission spectroscopy is used to identify and quantify the elements. The high temperature of the plasma limits interferences and ICP has broader application (e.g., for waste water analyses) than atomic absorption (AA) spectroscopy for metals analyses, but it has lower detection power.

Inert Media

Synthetic resin beads or water treatment materials that are nonreactive.     Inert media are used as a neutral nonreactive layer to more effectively separate the cation resin from the anion resin in mixed bed deionizers in order to regenerate each separately.

Infiltration

The movement of water into rocks or soil through interstitial pores, small cracks, or crevices in the soil or rock.

Infiltration Gallery

A subsurface groundwater collection system, typically shallow in depth, constructed with open-jointed or perforated pipes that discharge collected water into a water-tight chamber.     From this chamber, the water is pumped to treatment facilities and into the distribution system. Infiltration galleries are usually located close to streams or ponds and may be under the direct influence of surface water.

Infiltration Rate

Quantity of water (usually measured in inches) that will enter a particular type of soil per unit time (usually one hour).

Influent

The stream of water to be treated as it flows into any kind of water treatment unit or device, such as hard water into a softener or turbid water into a filter.

Ingestion

Type of exposure in which a substance is introduced through the mouth.

Inhalation

Type of exposure in which a substance is introduced through the lungs.

Inhibitor

Any chemical substance that is added to a water supply (or solution of any kind) which interferes with ("inhibits") a chemical reaction.     For example, inhibitors are sometimes used to help prevent precipitation or corrosion.

Initial Compliance Period

The first full three-year compliance period which begins at least 18 months after promulgation.

In-line Filtration

The addition of chemical coagulants directly to the filter inlet pipe.     The chemicals are mixed by the flowing water. Flocculation and sedimentation facilities are eliminated. This pretreatment method is commonly used in pressure filter installation.

Inorganic Matter

Chemical substances which do not arise from the process of living growth, are composed of matter other than plant or animal matter, and don't contain hydrocarbons or compounds of basically carbon structure.

In-parallel Flow

A piping arrangement which directs separate streams through two or more units of a treatment system in a balanced manner, with equal flow to each device, so that a higher total flow rate than that from a single unit can be achieved.

Input Horsepower

The total power used in operating a pump and motor.    Input HP = (brake HP)(100%) / motor efficiency, %

Insecticide

Any substance or chemical formulated to kill or control insects.

In-series Flow

A piping arrangement in which the entire effluent flow from one unit of a water treatment system is fed to a second succeeding unit.     This arrangement forces the water through multiple treatment units and achieves greater reduction of contaminants than can be achieved by a single pass of water through a single unit.

Installation

The connecting or setting up and startup operations of any water treatment system.   The term also refers to complete assembly of piping, valves, drain line, pumps, meters, and controls by which the equipment is connected into the water supply system.

In-Stream Uses

Water uses that can be carried out without removing the water from its source, as in navigation and recreation.

Integrated Exposure Assessment

A summation over time, in all media, of the magnitude of exposure to a toxic chemical.

Interface

The surface which forms a common boundary between two spaces or two parts of matter, such as the surface boundary formed between oil and water.     The term "interface" is often used to refer to the space between two different ion exchange resins in a mixed bed or to the resin surface at the regeneration grid in a mixed bed deionization system.

Interflow

Lateral movement of water in the upper layer of soil.

Interlock

An electrical control unit which delays the regeneration of one ion exchange unit while another unit is in the regeneration cycle.

Intermittent Flow

The interrupted patterns of water usage which occur in the home or in commercial businesses opposed to the steady constant flow patterns common in industry, such as in factories.     This term may also be used to refer to "on-off" flow patterns of water through treatment units specified in testing standards to simulate customer water use patterns.

Internal Friction

Friction within a fluid (water) due to cohesive forces.

Internal Water Treatment

Water treatment processes involving the addition of chemicals to the makeup water used in steam generation for boiler operations.     Chemicals are often added to prevent scale buildup or corrosive pitting of metal in boiler system components.

Interspecies Extrapolation Model

Model used to extrapolate from results observed in laboratory animals to humans.

Interstate Carrier

Any vehicle or transport which conveys passengers in interstate commerce.

Interstices

The pores or other spaces which are not occupied by solid matter and may be found between filter medium particles, ion exchange resin beads, or other similar treatment media.     Interstices may be occupied by air, water, or other gaseous or liquid material.     This term is also used to refer to similar spaces between natural soil or rock particles; and spaces between atoms or molecules in solids.

Invert

The lowest point of the channel inside a pipe, conduit, or canal.

Iodine

(I<sub>2</sub>)  A nonmetallic element which is the heaviest and least reactive of the naturally-occurring halogens.     It may be used for disinfection. In both its liquid and vapor forms, iodine is readily adsorbed by activated carbon.

Iodine Number

A measure of the ability of an activated carbon product to adsorb substances with low molecular weights.     The iodine number of a carbon is equal to the milligrams (mg) of iodine that can be adsorbed on one gram of activated carbon.

Ion

An atom or radical (group of atoms such as SO<sub>4</sub><sup>2-</sup) which carries an electrical charge as the result of having lost or gained electrons.     Positively-charged ions are called cations; negatively charged ions are called anions. An ion often has entirely different properties than the element (atom) from which it was formed.

Ion Exchange

A reversible chemical process in which ions from an insoluble permanent solid medium (the "ion exchanger"--usually a resin) are exchanged for ions in a solution or fluid mixture surrounding the insoluble medium.     The superficial physical structure of the solid is not affected. The direction of the exchange depends upon the selective attraction of the ion exchanger resin for the certain ions present and the concentrations of the ions in the solution.     Both cation and anion exchange are used in water conditioning. Cation exchange is commonly used for water softening.

Ion Exchange Membrane

A water-tight and electrically-conductive membrane which is either ion exchange resin cast in sheet form or powdered ion exchange resin laminated to a membrane fabric.     Both anion and cation ion exchange membranes are used in electrodialysis treatment systems.

Ion Exchanger

A permanent insoluble material (usually a synthetic resin) which contains ions that will exchange reversibly with other ions in a surrounding solution.     Both cation and anion exchangers are used in water conditioning. The volume of an ion exchanger is measured in cubic feet (or cubic liters) of exchanger after the exchanger bed has been backwashed and drained and has settled into place.

Ionic Concentration

A measure of the concentration of any ion in solution, usually expressed in moles per liter.

Ionic Constant

A measure in absolute units of the extent to which a chemical compound or substance in solution will dissociate into ions.

Ionic Weight

The weight of an ion as determined by the sum of the atomic weights of its components.

Ionization

The process in which a chemical combination breaks up into simpler electrically-charged components (individual atoms or groups of atoms) called ions.     The ionization process is related to the gaining or losing of electrons causing the atoms or group of atoms to become electrically charged.     The term "ionization" is sometimes used as if it had the same meaning as dissociation.

Iron (Fe)

A very common element often present in groundwater in amounts ranging from 0.01 to 10.0 ppm (mg/L).     Iron may be found in three forms:     In soluble form such as in ferrous bicarbonate;   Bound with a soluble organic compound; and   As suspended ferric iron particles.   Iron above 0.3 mg/L is objectionable in water because of staining of laundry and plumbing fixtures caused by the oxidation and precipitation of ferric hydroxide and/or ferric oxide (ferric iron) into small solid iron particles. Iron can also give a metallic or distorted flavor to beverages.     Iron also occurs in water as ferric iron.

Iron Bacteria

Bacteria which thrive on iron and are able to actually use ferrous iron (as found in water or steel pipes) in their metabolic processes, to incorporate ferric iron in their cell structure, and to deposit gelatinous ferric hydroxide iron compounds in their life processes.    Iron bacteria are found in several varieties including Crenothrix, Lepothrix, and Gallionella.     Iron bacteria can cause staining, plugging, and taste and odor problems in a water system.

Iron Fouling

The accumulation of iron on or within an ion exchange resin bed or filter medium in such amounts that the capacity of the medium is reduced.

Irreversible Effect

Effect characterized by the inability of the body to partially or fully repair injury caused by a toxic agent.

Isotherm

The measurement which represents the relationship between the mass of the substance adsorbed (adsorbate) at a given temperature and the mass of the adsorbent.

Isotope

One of two or more atoms or elements which have the same atomic number (occupy the same position in the periodic table) but which differ in other respects such as atomic weight and number of neutrons in the nucleus.

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Updated on Mon, 22 Jun 2020 by Jonathan

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