calcium - One of the principal elements in the earth's crust. When dissolved, in water, calcium is a factor contributing to the formation of scale and insoluble soap curds which are a means of clearly identifying hard water.

calcium carbonate equivalent - A common basis for expressing the concentration of hardness and other salts in chemically equivalent terms to simplify certain calculations; signifies that the concentration of a dissolved mineral is chemically equivalent to the stated concentration of calcium carbonate.

calcium hypochlorite - A chemical compound, [Ca(Cl 0)24H2O], used as a bleach and as a source of chlorine in water treatment; specifically useful because it is stable as a dry powder and can be formed into tablets.

capacity - An expression of the quantity of an undesirable material which can be removed from water by a water conditioning medium, i.e., cleaning, regeneration or replacement, as determined under standard test conditions. For ion exchange water softeners, the capacity is expressed in grains of hardness removed between successive regenerations and is related to the pounds of salt used in regeneration. For filters, the capacity may be expressed in the length of time or total gallons delivered between servicing.

capacity curve - A graph of the capacity versus regenerant levels for an ion exchange unit or system.

capillary action - A phenomenon in which water or many other liquids will rise above the normal liquid level in a tiny tube or capillary, due to attraction between molecules of the liquid for each other and the walls of the tube.

carbonaceous - Materials of or derived from organic substances such as coal, lignite, peat, etc.

carbonaceous exchanger - Ion exchange material produced by the sulfonation of carbonaceous matter.

carbonate - The CO32 ion.

carbonate alkalinity - Alkalinity due to the presence of the carbonate ion (CO32).

carbonate hardness - Hardness due to the presence of calcium and magnesium bicarbonates and carbonates in water; the smaller of the total hardness and the total alkalinity. (See temporary hardness.)

carbon chloroform extract - The matter adsorbed from a stream of water by activated carbon, and then extracted from the activated carbon with chloroform, using a specific standardized procedure; a measure of the organic matter in a water.

carbon dioxide - A gas present in the atmosphere and formed by the decay of organic matter; the gas in carbonated beverages; in water it forms carbonic acid.

carbonic acid formed - It does not contribute to total dissolved solids, but does have a pronounced effect on specific resistance. This effect must be included when estimating the water quality from a weak base deionizer. Carbonate and bicarbonate alkalinity are destroyed by cation resin and converted to carbonic acid. To calculate carbonic acid formed add the carbonates, bicarbonates, and twice the carbon dioxide.

carboxylic - An organic acidic group (COOH) which contributes cation exchange ability to some resins.

cartridge - Any removable preformed or prepackaged component containing a filtering media or ion exchanger.

cathode - The negative pole of an electrolytic system; an electrode where reduction occurs. (See anode.)

cathodic protection - A corrosion control system in which the metal to be protected is made to serve as a cathode, either by the deliberate establishment of a galvanic cell or by impressed current. (See anode.)

cation - An ion with a positive electrical charge. Calcium, magnesium and sodium are cations.

cation exchange - Ion exchange process in which cations in solution are exchanged for other cations from an ion exchanger.

cation load factory y - This is the sum of calcium, magnesium, sodium, and potassium. It is the sum of all cations.

caustic - Any substance capable of burning or destroying animal flesh or tissue. The term is usually applied to strong bases.

caustic soda - The common name for sodium hydroxide.

CC - Abbreviation for "carbon chloroform extract".

channeling - The flow of water or other solution through a limited number of passages in a filter or ion exchanger bed, instead of distributed flow through all passages in the bed. May be due to fouling of the bed and plugging of many passages, poor distributor design, flow rates which are too low, faulty operational procedures, or other causes.

chelate - To form a complex chemical compound in which an ion, usually metallic, is bound into a stable ring structure.

chelating agent - A chemical compound sometimes fed to water to tie up undesirable metal ions, keep them in solution, and eliminate or reduce the normal effects of the ion. (See sequestering agent.)

chemical stability - Resistance to attach by chemical action.

chlorides - Salts of chloride are generally soluble. High concentrations contribute to corrosion problems.

chlorine - A gas, C2, widely used in the disinfection of water and an oxidizing agent for organic matter, iron, etc.

chlorinator - A device designed to feed chlorine gas or solutions of its compounds, such as hypochlorite, into a water supply.

chlorine demand - A measure of the amount of chlorine consumed by oxidizable substances in a water before a chlorine residual will be found.

coagulant - A material, such as alum, which will cause the agglomeration of finely divided particles into larger particles which can then be removed by settling and/or filtration.

coagulant aid - A material which is not a coagulant, but which improves the effectiveness of a coagulant by forming larger or heavier particles, speeding the reactions, or by permitting reduced coagulant dosage.

coagulation - The process in which very small, finely divided solid particles are agglomerated into larger particles.

COD - The abbreviation for "Chemical Oxygen Demand".

Coliform bacteria - A group of microorganisms used as indicators of water contamination, and the possible presence of pathogenic (disease producing) bacteria.

collector - A device or system designed to collect backwash water from a filter or ion exchange bed. May also be used as an upper distributor to spread the flow of water in downflow column operation. (See distributor.)

colloid - Very finely divided solid particles which do not settle out of a solution; intermediate between a true dissolved particle and a suspended solid which will settle out of solution. The removal of colloidal particles usually requires coagulation.

color - The shade or tint imparted to water by substances in true solution, and thus not removed by mechanical filtration; most commonly caused by dissolved organic matter, but may be produced by dissolved mineral matter. As measured in a water analysis, only the intensity of yellow color is reported.

color throw - The discharge of color to the effluent of a filter or ion exchange system by any component. It usually occurs after a period of standing which allows slowly soluble colored matter to accumulate in the system.

column operation - The process in which the solution to be treated is passed through a bed, or column (as in a tank), of filter media or ion exchanger; may be either upflow or downflow.

combined available chlorine - The chlorine present as chloramine or other chlorine derivatives in a water, but still available for disinfection and the oxidation of organic matter. Combined chlorine compounds are more stable than free chlorine forms, but are somewhat slower in disinfection action.

compensated hardness - A calculated value based on the total hardness, the magnesium to calcium ratio and the sodium concentration of a water. It is used to correct for the reductions in hardness removal capacity caused by these factors in zeolite exchange water softeners. No single method of calculation has been widely accepted.

composite sample - A mixture of a number of single or "grab" samples, intended to produce a typical or average sample. May be made up of equal volumes of individual samples, or of single samples proportioned to variations in flow or usage.

concentration factor - A number used to estimate the scaling potential in reverse osmosis systems when the TADS rejection is expected to exceed 90%; equal to the reciprocal of 1 minus the recovery ratio. When multiplied by the feed TADS, the result is the approximate waste water TADS. (See recovery, rejection.)

conductance - In water conditioning, the readiness of water to carry electricity; the reciprocal of electrical resistance. The unit of measure for conductance is the mho (reciprocal ohm). Used to approximate the dissolved solids content of water. (See conductivity, resistance, specific conductance.)

conductivity - The quality or power to carry electrical current; in water; related to the concentration of ions capable of carrying electrical current. (See conductance, electrolyte.)

connate water - Water deposited simultaneously with rock and held with essentially no flow; usually occurs deep in the earth, and usually is high in minerals due to long contact.

contamination - The presence of foreign matter in a substance which reduces the value of the substance, or interferes with its intended use.

conversion - See "recovery".

corrosion - The disintegration of a metal by electrochemical means.

Crenothrix polyspora - A genus of filamentous bacteria which utilize iron in their metabolism, and cause staining, plugging and taste and odor problems in water systems. (See iron bacteria.)

cross connection - A direct link between a potable water system and a non-potable water system, which permits undesirable substances to be drawn into the potable water.

cross-sectional area - The area of a plane at a right angle to the direction of flow through a tank or vessel; often expressed in square feet, and related to the flow rate. (Example: 5 gallons per minute per square foot of ion exchanger bed area.)

Cryptosporidium - A common intestinal parasite found in waters contaminated by sewerage or runoff containing animal waste. It causes diarrhea, nausea, and cramps. Individuals with weakened immune systems are at particular risk. Although resistant to chlorine and most oxidizing agents, it is effectively removed by filtration to 1 micrometer, and can be destroyed by boiling.

cube - A slang expression sometimes used to mean a cubic foot of ion exchanger or filter media.

cubic foot - The volume of a cube whose sides have the length of one foot. The common basis for the measurement of the volume of ion exchangers or loose filter media.

cycle - A series of events or steps which ultimately lead back to the starting point, such as the exhaustion-regeneration cycle of an ion exchange system.