The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1903-11-08

ing, In scale, 100000 gallons passing through
a surface of one acre. This sewage, which
passes into the tank directly from the two
great arteries of the Boston sewage sys-
TEN, comes out at the end Of twenty-four
hours as a clear, colorless liquid that might
even be drunk with impunity. A glass jar
of sewage, after its experience in the sand
filter, closely resembles in appearance one
Of the glass jars Of mineral water that you
purchase at the apothecary's. And this APP
parently miraculous result has been &C
complished, not by the process of straining,
but by the bacteria that were originally In
the sand of the filter and which have been
prodigiously multiplied In number under the
favorable conditions provided for them
particularly the presence of plenty of air
and the regular supply Of sewage. The
chemical action of these bacteria, which
exist practically on the surface of sand or
stone is to transform the decaying matter
into nitrates and nitrites, thus supplying
plant life with necessary food as well as
renewing the supply of nitrogen that vege-
tation is also constantly taking from the
air and soil. The number of them in a
given filter varies with the age of the filter,
the character of the sand and the way it is
by the fact that it has been estimated that
for each grain of sand near the top Of the
filter there may be as many as 5000 900 mi
crobes. The conditions under which these
microbes flourish are the direct opposite of
those that support the disease germs, and 1t
is fact that the baneful little organisms
cannot survive the passage through the fl
ter in which the good bacteria live, multi
ply and purify.
UNLIKE DISEASE BACTERIA.
The sand filter, however, is not every
where practicable as it is in Massachusetts,
where sand is plenty and the vast quanti-
ties of it necessary to purify the sewage of
large city readily obtainable. Other pro-
cesses, therefore, may be seen in tanks of
the institute laboratory, looking toward SUBJ
stituting crushed rock of various sizes and
used in connection with the septic or
sealed tanks in which the anaerobes carry
on the beginnings of the publication pro-
cess. In this case the sewage passes from
the Boston system into the septic tank and
from that tank into another filled with
crushed rock, the process being quicker
than the sand filter, although two tanks in
stead of one are involved in 1t. The action
bacteria are generally caled-is the same
as in the case of the sand filter. except that
they are not so closely distributed.
These organisms. so far as they have yet
been studied, present a curious contrast to
the disease germs that have been so much
more completely investigated The great
difference, as shown by the two that have
recently been isolated from their fellows
in the sand filter of the institute labora-
tory-not individually, Of course, but in the
colonies" that become visible when the
bacteriologist succeeds in inducing an in
visible but suspected microbe to develop
until there so many of him that the
groups may be seen spotted over the surface
of the glass plate on which he has been
placed to multiply-lies in the question of
nourishment. The ordinarily jely-like solu-
lions of rich food matter I'm which the dis
ease bacteria multiply so rapidly apparently
offer no sustenance whatever to the nitrify-
ing bacteria. The latter must be cultivated
in an acid jelly-a fact that further justifies
the theory of their action upon sewage.
Just at present the establishment Of this
new institute laboratory, which is under the
direction of Professor w. T. Sedgwick
whose biological research work has already
done so much to counterfeit the danger of
contamination of municipal water supplies
through presence of sewage, is considered
particularly significant. Sewage purifica-
ton offers problems that increase In magni-
tude as our cities grow in population, and
immense sums of money have already been
spent on such plans as that by which Chi
cago, through its drainage canal, is sending
its sewage into the Mississippi river. Var
ious efforts, in fact, are looking toward a
satisfactory solution of this growing munic-
ipal problem. The results, therefore, of the
new technology laboratory. now daily tap
ping the sewage of Boston, quietly compar-
ing the results of different methods of rem
dering it harmless to humanity and sys-
tematically seeking a scientific acquaint-
ance with the countless bacterial agents
which nature has furnished and which man
has only lately discovered, bid fair TO make
the modest wooden structures in which II
has housed itself memorable objects In the
history OF applied science