View report page

73
known as the Ammoniator, which enables accurate dosage to be
made and is quite simple to operate. The dosage is usually in the
ratio of 1/8 to 1/2 of that of chlorine, and is always added to the
water after filtration, and before the chlorine.
As in all forms of scientific research, discoveries are bound to
occur, and such is the case with regard to the sterilisation of
swimming bath waters. Research and development work followed
by extensive field experiments, have demonstrated that through the
adoption of a new technique the bactericidal efficiency of the
chlorination treatment can be greatly increased. In addition,
chlorine may be made to perform many other useful functions in
the purification process. Chlorine is now being used as an aid to
coagulation for improvement of colour, for elimination of objectionable
taste and odour, and for the prevention of various growths
in storage reservoirs, purification works and distribution systems.
In order to understand and assess the value of the recent discoveries,
it is perhaps desirable to review briefly the history and
advancement of the three different chlorination methods previously
used, i.e. :
(i) Simple chlorination;
(ii) Chlorine/ammonia treatment (the chloramine process);
(iii) Chlorination and dechlorination.
Simple chlorination as first introduced for the sterilisation of
public drinking water was found quite effective in eliminating
pathogenic bacteria, but certain disadvantages soon became
apparent. Unpleasant tastes were often produced unless the water
was practically free from organic and inorganic impurities, and it
was also found that the chlorine residual disappeared quickly.
The development of the chloramine process consisting of combining
ammonia with chlorine to form chloramine compounds, was
a distinct step forward which materially helped in overcoming the
disadvantages of simple chlorination, but introduced other problems
due to the fact that the oxidising potential of the chloramine compounds
is much lower than that of chlorine alone.
Chlorination and dechlorination have been used in a somewhat
haphazard way in order to take advantage of the rapid sterilising
effect of simple chlorination without having a residual in the distributing
system. Generally speaking, the process was applied