Glossary Of Water Treatment Industry Terms . . ."R"
rated capacity- The basis
for calculating the period of time, or number of gallons delivered by
a water softener, filter, or deionizer, between regenerations or servicing,
as determined under specific test conditions. (See rated in-service life,
rated softener capacity.)
rated in-service life - The
length of time or total gallons delivered between servicing of the media
in a filter as determined under standard test conditions.
rated pressure drop - The
pressure drop of a water softener or filter at the rated service flow,
with clean water at a temperature of 60oF, with a freshly regenerated
and/or backwashed softener or filter, as determined under standard test
rated service flow - The
manufacturer's specified maximum flow rate at which a water softener will
deliver soft water, or a filter will deliver quality water as specified
for its type, as determined under standard test conditions. A manufacturer
may also specify a minimum flow rate or a range of service flows.
rated softener capacity -
A water softener capacity rating based on grains of hardness removed
while producing soft water between successive regenerations, and related
to the pounds of salt required for each regeneration, as determined under
standard test conditions.
raw water- Untreated water,
or any water before it reaches a specific water treatment device or process.
recovery- In reverse osmosis
processes, indicates the amount of product water taken from the feed water
stream; expressed as a percentage of product water flow rate to feed water
flow rate. (See concentration factor.)
reduction - A chemical process
in which electrons are added to an atom, ion or compound, causing the
substance's valence to decrease. Whenever reduction occurs, an off-setting
oxidation reaction must occur. (See oxidation.)
red water- Water which
has a reddish or brownish appearance due to the presence of precipitated
iron and/or iron bacteria.
regenerant- A solution of
a chemical compound used to restore the capacity of an ion exchange system.
Sodium chloride brine is used as a regenerant for ion exchange water softeners,
and acids and bases are used as regenerants for the cation and anion resins
used in demineralization.
regeneration - The
process of restoring an ion exchange medium to a usable state after exhaustion.
In general, it includes the backwash, regenerant introduction and fresh
water rinse steps necessary to prepare a water softener exchange bed for
service. Specifically, the term may be applied to the step in which the
regenerant solution is passed through the exchanger bed (salt brine for
softeners, acid and bases for deionizers.
regeneration level - The
quantity of regenerant used in the regeneration of an ion exchange unit
or system, usually expressed in pounds per regeneration and/or pounds
per regeneration per cubic foot of ion exchanger.
rejection - In reverse osmosis
processes, the degree of removal of dissolved salts from the feed water
as it passed through a semipermeable membrane (also called "salt
rejection"); expressed as a percentage of the feed water TDS. (See
total dissolved solids.)
residual - The amount
of a specific material remaining in the water following a water treatment
process; may refer to material remaining as a result of incomplete removal
(see leakage), or to material meant to remain in the treated water. (See
residual chlorine - Chlorine
remaining in a treated water after a specified period of contact time
to provide continuing protection throughout a distribution system; the
difference between the total chlorine added, and that consumed by oxidizable
matter. (See combined available chlorine, free available chlorine.)
resin- Synthetic organic
ion exchange material, such as the high capacity cation exchange resin
widely used in water softeners.
resistance - In water
conditioning, the opposition offered by water to the flow of electricity
through it; the reciprocal of electrical conductance. The unit of measurement
for electrical resistance is the Ohm. Electrical resistance can be used
to approximate the mineral content, or lack of it, in high quality water.
resistivity- A capacity
for resisting the flow of electricity. (See resistance.)
reverse deionization - The
use of the anion exchange resin ahead of the cation exchange resin (the
reverse of the usual order), in a deionization system.
reverse osmosis - (R.O.)
A process that reverses, by the application of pressure, the natural process
of osmosis so that water passed from the more concentrated to the more
dilute solution through a semipermeable membrane, thus producing a stream
of water up to 98% free of dissolved solids.
rinse - That portion of the
regeneration cycle of an ion exchanger in which fresh water is passed
through the column to remove spent and excess regenerant, prior to placing
the system in service.
R. O. - The abbreviation for "reverse osmosis".