The Disposal of Wastes from Country Houses 
surfaces of the filter beds. (2) The use of tanks 
conveniently hides from sight the few floating ob¬ 
jects, such as pieces of orange peel, which are not 
broken up in passage through the sewers, and which 
may offend the eye. (3) That, as the constituency 
of sewage is of the most variable character, contain¬ 
ing acids and alkalis, it is beneficial, especially in 
cases where factory wastes are permitted to enter 
the sewers, that provision should be made for the 
blending of these varying mixtures. (4) Because 
the anaerobic action, which takes place in tanks 
correctly designed and operated, has been found 
not only to liquefy and gasify much of the solids in 
sewage, but also so to separate the particles and bring 
about other changes, as enables many times the 
volume to be treated on a given area, than would 
otherwise be practicable. 
The capacity of these tanks should not permit of 
a storage of more than a single day’s supply,( some 
authorities favoring as little as eight hours’ detention), 
and its passage arranged so that the entire contents 
(with the exception of the small percentage of matters 
in suspension), will be expelled by the following day’s 
inflow. If this is not accomplished, the poisonous 
excretions of the bacteria themselves will cause the 
sewage to come to an unhealthy condition, and in¬ 
stead of aiding in the work of purification, will de¬ 
feat it. In the most successful examples, less than 
10 c / 0 of the suspended solids passes from these tanks, 
hence, 90% is kept from interfering with the 
subsequent treatment of the invisible organic 
matters which are in solution, and which, be 
it remembered, form 3"4ths of the polluting matters 
in sewage waters. Complying with the conditions 
governing the mineralization of animal and vegetable 
matter in liquid form is the most important require¬ 
ment in sewage purification, but the i-4th of solids 
in suspension, when not satisfactorily handled, is 
the most troublesome part of sewage treatment. 
More is yet to be learned in regard to this matter 
from the experience of those who have designed and 
installed the most recent sewage works, but sufficient 
is known to enable a clear distinction to be drawn 
between resolution tanks and filter beds, con¬ 
structed consistent with a previous knowledge of 
the governing conditions, and those which have been 
designed in a haphazard fashion, of which unfor¬ 
tunately there are too many examples. 
In relation to the second stage of sewage purifica¬ 
tion, if the volumes of sewage are not divided by 
natural or mechanical means, so as to avoid suffo¬ 
cating the very bacteria which for their life pur¬ 
poses require abundance of air, it is only to be ex¬ 
pected that disappointment will be met with. 
There are five methods by which sewage oxidation 
may be successfully accomplished. It is seldom, 
however, that local conditions do not point the ex¬ 
perienced expert to the adoption of one, or it may 
be a combination of two or more of these methods. 
In referring briefly to these, we would ask the 
reader to bear in mind that the object in each case 
is that of providing sewage as food for bacteria 
which require air also, and yet are so minute that 
500,000 may easily inhabit a single drop of liquid. 
Land Treatment .—This may be by broad irriga¬ 
tion, as in the case of sewage farms, where crops 
are raised and cattle fed, but which are operated 
with the primary object of disposing of sewage. In 
case of single residences, surface or subsurface ir¬ 
rigation is employed, in which sewage is flushed 
intermittently over a sloping surface of ground, or 
into “ fields ”of open jointed drain pipes sunk beneath 
the surface. In the use of these processes it is in¬ 
tended that the sewage shall be absorbed by the soil, 
and destroyed by the bacteria inhabiting it. The 
character of the ground, its location, area available, 
the volume of sewage to be handled, 
the manual attention necessary, are 
a few of the governing factors in the 
selection or rejection of this method. 
Intermittent Subsidence Through 
Sand .—Provided that the grains of 
sand are of the right size, and that 
sewage is fed in intermittent doses of 
suitable volume, the liquid will be 
prevented from passing downwards 
too rapidly, and will be intermixed 
with sufficient air found in the voids 
in the sand to effect bacterial oxida¬ 
tion. This is a method than which 
there is no better, where all condi¬ 
tions are favorable, and by which 
upwards of ten times the volume 
treated by the last named method 
may be satisfactorily purified, 
and at a less cost for manual 
ANAEROBIC BACTERIA WHICH LIQUEFY SOLIDS IN THE 
ABSENCE OF AIR 
189 
