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3.10.2 Gravity water filter
Filtration is defined as the passage of a liquid through a filter
and accomplished via gravity, pressure, or vacuum. Filtrate is
the liquid that has passed through the filter. The purpose of
filtration is to remove particulate matter from the liquid. When
using a gravity water filter fitted with and reusable ceramic
candle filter of 0.9 micro meter porosity, most bacteria,
parasitic microorganisms and suspended particles can be
removed from the water but not dissolved salts.
3.10.3 Deionizer
Deionizer is an apparatus used to produce ion free water.
Deionizartion is a process in which chemically impure water is
passed through anion and cation exchange resins to produce
ion free water. Deionized water has low electrical conductivity,
near neutral p
H
and is free from water-soluble salts but is not
sterile. Cations, which may be present in the water such as
calcium, magnesium and sodium, are exchanged by the
cation resin, which in turn releases hydrogen ions. Anion
impurities such as sulfate, bicarbonate, silicate, nitrate and
chloride are exchanged by the anion resin, which in turn
releases hydroxyl ions. Finally, the hydrogen ions combine
with the hydroxyl ions to give ion - free water.
N.B: Deionizer resin can cause irritation if it is allowed to
enter the eye or skin. It is therefore, advisable to wear plastic