Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1899-03-01


two of these sources are available to
any municipality. and each communi-
~ is compelled 10 accept the source
of is supply in accordance with its
local condition and environments.
The larger cities have almost uni
versallv been forced to seek their sup
ply of water from lakes. by the con-
struction of impounding reservoirs.
or from running streams. In but few
instances has ii been found practical
BILE for cities with n daily cOnsump-
ton of more than five million of gal
Ions to procure their supply from
subterranean sources. Cities situated
near to lakes and large streams of
running water have quite generally
availed themselves of these sources.
Contamination by Sewage.
While each city is careful to draw
its supply from a point free from
contamination by its sewage, vet it is
compelled to use the water contami-
mated bv the sewage of all the cities
above, and it in turn contributes to
the contamination of the water supply
of all cities below. This fact alone
demonstrates the necessity of the
general government or the state au-
thorities taking such measures as
NAV be necessary to prevent the pollu-
ton of publrc water supplies and to
protect the people in their inherent
right to the use of uncOntaminated
water that natu''e has given them.
During certain seasons of the year
when the rivers are high and at the
time OF the breaking up of the ice the
-1t,fr
suspension large amounts of earth
and organic matter. These condi-
lions have made it necessary tor mu-
inequalities drawing their water sup
plies from such sources to provide
means for Qualification and purifica-
ton.
The practice of purifying water
for dome este use is not modern, for
we read in ancient history that the
Egyptians purified the water from the
river Nile by sedimentatiOn and coagu-
lation. The problem of the purifca-
ton and Qualification of water upon Il
large scale for the use of municipali-
ties has been developed during the
last century. The publication of wa
ter in its modern development en-
braces aeration, sedimentation and
filtration. There are two general
systems OF filtration, viz: The En-
glish system, or slow sand filtration,
and the American system, commonly
called mechanical filtration.
The American system of filtration
consists of Introducing into the water
to be filtered sufficient quantity of
coa@ulent, usually sulphate of alumni
nuia. for the purpose of precipitate
impurities in the water. The water
is then passed through a bed of sand
or quartz of about three-and-a-half
feet in depth. The sand or quartz is
confined in a wooden or steel tank,
which is provided with the necessary
pipes and valves. The precipitation
forms a film or covering on the sand
bed which assists in the process of
filtration. This film finally becomes
50 thick or heavy as to prevent the
p passage of the necessary amount of
water through the filter.
o.. Cleaning of Filters.
The filter is cleansed by revers-
ing the current of water, and by oper-
ating a mechanical device for stirring
the sand ut the same time. The rate
of of filtration by the American sys-
tenn is from 80 to IS times that of
the English system. This system is
now in use in many of the smaller and
some of the larger cities of America.
The English system of filtration con-
sists of passing the water through a
bed of sand about four feet thick
placed upon stratiiied layer of gravel
or broken stone about one foot thick,
in n shallow reservoir or basin pro-
vided with suitable inlet pipes and
under-drains,
The impurities soon force n gela-
tinous coating over the sand which
materially increases the efficiency of
the filter. When this coating becomes
so thick as to prevent the flow of the
water through the sand at the rate
required the water is drawn off and
the surface is scraped, thus removing
the film. The rate at which it has
been found practicable to filter water
by this process ranges from Loo, 900
to ), 900. 900 gallons per acre in "a
hours, depending upon the character
of the water and the construction of
the sand bed. The English system
OF filtration was first extensively used
in England about fifty years ago and
afterward introduced into Germany
and other European countries.
1t was first introduced into this
country about twenty-five years ago,
and is now in USE in the cities of
Poughkeepsie. Hudson, Albany and
Mt. Vernon, y. Y: Lawrence and
Nantucket. Mass, Ashland, Wis and
other small cities.
This system of filtration has been
recommended for the publication of
the water supply of the city of Phila-
delphia by the commissioner of pub
lie works. From the report OF the
above named commissioner we learn
that the bacterial efficiency of the
ENGLISH Governmental filters for a con-