Flow  of water in a pipe or line in a direction opposite to the normal flow;  often associated with back siphonage or the flow of possibly  contaminated water into a potable water system.

A device or system installed in a water line to stop backflow from a non-potable source.

Pressure which creates resistance against the flow of water.

The  upflow or counter-current flow of water through a filter or  ion-exchange medium, lifting the mineral bed and flushing away to the  drain the particles of foreign matter that have been filtered from the  water supply during the service cycle.

Unicellular  microorganisms which typically reproduce by cell division. Although  usually classed as plants, bacteria contain no chlorophyll. Many  different types of bacterial organisms are often found in drinking  water. Most municipally treated water is essentially bacteria free due  to the addition of chlorine. Some forms of cyst type viruses have a  degree of immunity to chlorine due to the cocoon-like shell around the  virus. These types of organisms such as Giardia Cyst, Giardia Lamblia,  and Cryptosporidium have a physical size of three to seven microns and  can be effectively removed by sub-micron filtration. Some bacteria are  helpful to man, others harmful.

Having  the ability to inhibit the growth of bacteria without destroying them.  For example, silver impregnated activated carbon will limit bacterial  colonization but not eliminate it.

Any substance or agent which kills bacteria.

A unit of pressure. One bar equals 14.5 pounds per square inch (psi) or about 0.987 standard atmospheres.

An  alkali that releases hydroxyl ions when dissolved in water. Bases reset  with acids to form a neutral salt and water. In general they taste  bitter rather than sour, and feel slippery and reverse the color changes  produced by acids in indicators. For example, they turn litmus paper  blue.

The  utilization of ion exchange resins to treat a solution in a container  wherein the removal of ions is accomplished by agitation of the solution  and subsequent decanting of the treated liquid.

A mass of ion exchange resin particles or filter media contained in a column.

The  height of the resin or filter media in the column after it has been  properly conditioned for effective operation, usually expressed in  inches. This depth excludes any supporting bed.

The  effect produced during backwashing: the resin particles become  separated and rise in the column. The expansion of the bed due to the  increase of the space between resin particles may be controlled by  regulating backwash flow.

The  presence in a solution of hydroxyl (OH-) ions resulting from the  hydrolysis of carbonates or bicarbonates. When these salts react with  water, a strong base and a weak acid are procured, and the solution is  alkaline.

A  chemical which can kill or inhibit the growth of lining organisms such  as bacteria, fungi, molds, and slime. Biocides can be harmful to humans.

Subject  to degradation into similar substances by biological action . Examples  include detergents, sewage, and other organic matter by bacteria.

The  trade name for a manganese dioxide coated aluminum silicate used as an  oxidizing catalyst filter medium for iron and manganese reduction.

The  withdrawal of water containing a high concentration of solids or  dissolved solids or maintain a specified solids-to-water concentration  ratio.

Abbreviation  for Biochemical Oxygen Demand. The amount of oxygen consumed in the  oxidation of organic matter by biological action under specific standard  test conditions. Widely uses as a measure of the strength of sewage and  wastewater.

A  black pigment substance with a carbon content of about 10 percent, made  by carbonizing animal bones. It is used as a selective anion exchanger  for fluoride and arsenic reduction.

Water containing bacteria between 1.000 and 15,000 ppm of dissolved solids.

The  first appearance in the solution flowing from an ion exchange unit of  unabsorbed ions similar to those which are depleting the activity of the  resin bed. Breakthrough is an indication that regeneration of the resin  is necessary.

A  strong solution of salt(s), such as the sodium chloride or potassium  brine used in the regeneration of ion exchange water softeners, but also  applied to the mixed sodium, calcium and magnesium chloride waste  solution from regeneration.

A device used to draw a solution such as brine from a storage tank and force it into a cation or anion water treatment unit.

A tank which sits beside the softening unit and acts as a salt storage and brine supply.

A chemical which causes a solution to resist changes in pH, or to shift the pH to a specific value.

A  connection or a valve system that allows untreated water to flow to a  water system while a softener or filter is being regenerated, backwashed  or serviced; also applied to a special water line installed to provide  untreated water to a particular tap, such as a sill cock.