The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1890-06-08
WATER FILTRATION.
Sand Filters Not Impervious to Bacteri
Interesting Experiments.

Sand Filters Not Impervious to Bacteria
Interesting Experiments.
The evidence which has been collected of
late years with regard to the efficiency of
filters of various kinds in removing from
water the specific germs of such diseases as
cholera and typhoid ia somewhat contradic-
Journal. As regards filtration OF munich
pal water supplies on the large scale by
means of sand, it has been shown by the ex-
periments of FARMLAND, of the Massachu-
setts state board of Health, and by the re-
suits obtained at Berlin and elsewhere, that
a very large proportion of the ordinary bac
terra are removed by such filtration If it is
not made to 90 on too rapidly.
A recent outbreak of typhoid fever in
Berlin has led to fresh and more careful
investigation of the effects of the sand
filters used in that city, and the results are
of much practical interest. For the eight
years, 188O-88, there was comparatively
little typhoid fever in Berlin, the annual
number of deaths from this cause being
only little over two in IL, GOO living popu-
lation. In the early part of 1879 an cpl
demic of about 700 cases of typhoid Oc-
CURED in the eastern part of the city,
Spree. taken through the sand filters at
Stralan. In the western part of the city,
supplied from Lake Teeei, there was little
or no typhoid.
This led to series of experiments by
Frankel and Plefke, which demonstrated
that a certain proportion of many form of
bacteria. and especially those Of cholera
and typhoid, do pass through the sand
filters. Their trials were first made with
the Bacillus violacens, because its presence
is easily recognized in gelatin cultures by
the blue-colored spots which it produces.
The Spree water, containing small amount
Of this peculiar organism, was passed
this being continued for thirty days.
Through one of these filters the water was
passed at the rate of 100 millimeters Per
hour, and through another with three
times this velocity. It was found that in
each filter, and from the very beginning Of
passed through, that when the filtration
went on slowly the proportion found in the
effluent was about per cent of that in the
supply. and that when the velocity of the
filtration was three times increased The pro-
portion of bacteria In the effiuent also in
creased to 8 per cent.
Having settled this, experiments were
next made with the bacillus of typhoid and
that of cholera in the same manner, and
with precisely the same results.
It appears, then, that a certain proportion
of dangerous bacteria will go through sand
ulteEBs anu buaG Tue dDSOluI0 NUMBER WHICH
pass depends on the number in the until
tered water, the rapidity of the filtration,
and the length of time during which the
filter has been used. No experiments seem
to have been made upon the effects of sue
cessive filtration, with intermediate aera-
tion-that is, the sending through fresh
sand filter the water which has already
passed through one filter. The effect Of
this would not be the same as that produced
by passing the water once through double
thickness of sand.
The French minister of war states, in q
recent report. that steps have been taken to
provide filters for all military posts where
thoroughly satisfactory drinking water for
the troops is not furnished. These are to
be porcelain filters of the Chamberlain
pattern, and it is estimated that for the
garrisons in France and Algeria about
1900 of these filter tubes will be required.
That something should be dome to secure
purer drinking water for the French
soldiers is evident from the great preva-
lence Of typhoid among them. and from
the fact that ont of 187 specimens of water
from different sources examined in the
laboratory of the military school of Val de
Grace. 81 contained bactaria of putrefac-
tion. Z contained the typhoid bacillus and
q were contaminated by human excreta.
II il more than doubtful whsther the
Chamberlain filters will remove all perms
after continuous use under pressure for