Glossary of Water Treatment Terms & Definitions - I



The water entering a water treatment devise.

Inorganic Matter

Matter which is not derived from living organisms and contains no organically produced carbon; includes rocks, minerals and metals.

In-parallel Flow

A piping arrangement which directs separate streams through two or more water treatment units in a balanced manner, providing equal flow to each device. The inlets of two or more units are connected together and the outlets are connected together such that water will flow through the units simultaneously.

In-series Flow

A piping system in which all of the effluent flow of one unit in a water treatment system is fed to a second and succeeding unit. This arrangement achieves a greater reduction of contaminants than can be obtained by the passage through a single unit.


An atom, or group of atoms in a solution which function as a unit, and has a positive or negative electrical charge, due to the gain or loss of one or more electrons. It is smaller than a colloid.

Ion Exchange

A reversible process in which ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution; the direction of the exchange depends upon the affinities of the ion exchanger for the ions present and the concentration of the ions in the solution. The ion exchanger media is an insoluble permanent solid medium. for a product offering.

Iodine Number

A measure of the ability of activated carbon to adsorb substances with low molecular weights. It is the milligrams of iodine that can be adsorbed on one gram of activated carbon.


The dissociation of molecules into simpler, electronically charged particles. It is related to the gaining or losing of electrons causing the atoms to become electronically charged.


An element often found dissolved in ground water (in the form of ferrous iron) in concentrations usually ranging from zero to 10 ppm (mg/l). It is objectionable in water supplies because of the staining caused after oxidation and precipitation (as ferric hydroxide), because of tastes, and because of unsightly colors produced when iron reacts with tannins in beverages such as coffee and tea. As little as 0.3 ppm of iron can cause staining. (See also ferrous iron, ferric iron, and heme iron).
See also Ferrous iron, Ferric iron

Iron Bacteria

Organisms which are capable of utilizing ferrous iron, either from the water or from steel pipe, in their metabolism, and precipitating ferric hydroxide in their sheaths and gelatinous deposits. These organisms tend to collect in pipe lines and tanks during periods of low flow, and to break loose in slugs of turbid water to create staining, taste and odor problems.

Iron Bacteria are actually living organisms, which feed on iron in water, iron pipes and fittings. They pose no health risk but can be very damaging to the plumbing system. These bacteria form a reddish-brown slime, which may clog pipes and fixtures. Occasionally this slime breaks loose causing spurts of extremely discolored water. Iron bacteria can be identified by reddish-brown or sometimes yellow, gelatinous formations on the surface of the water in toilet flush tanks or by slimy clumps of iron oozing form pipe leaks or corrosion. They can cause bad tastes and odors in the water supply.

Iron bacteria can not be treated by most common water filtration methods and can cause fouling in water treatment equipment. In extreme cases it can actually clog and destroy well pumps.

To treat this problem you must first kill the bacteria by chlorination or some other oxidizing-disinfecting method and then filter it out of the water.The well and all the piping must first be treated with heavy amounts of chlorine for an extended period of time, using a process known as "shock chlorination."

Iron Fouling

The accumulation of iron on and within an ion exchange resin or filter bed resulting in a reduced capacity of the media.