Installing a Small Sewage Disposal Plant 
THE LAST WORD ON SEWAGE DISPOSAL FOR COUNTRY HOUSES—WHAT THE SEPTIC 
TANK IS AND ITS LIMITATIONS—THE THREE ESSENTIALS FOR SEWAGE DISPOSAL 
BY Henry N. Ogden, C. E. 
Prof, of Sanitary Engineering, Cornell University 
Special Assistant Engineer New York State Department of Health 
U NDER whatever form the problem presents itself. Sewage 
Disposal is always a question of so treating a large volume 
of dirty water that it shall not then or thereafter cause disagree¬ 
able odors nor, in special cases, injure the quality of any drinking 
water into which it may be discharged. For sewage, it must al¬ 
ways be remembered, is chiefly water defiled with a small addi¬ 
tion of mineral, vegetable and animal matter, the proportion be¬ 
ing about one tablespoonful of mineral dirt and one tablespoonful 
of animal and vegetable matter to a barrelful of water. 
The problem consists in removing from the barrel these two 
tablespoon fills and doing it in such a way 
that there shall be no smell occasioned in 
the process. The cost of the process, 
moreover, should be reasonable. The 
method first thought of naturally involved 
a straining or sieve-action, but, unfor¬ 
tunately, the solids present are so fine that 
only a small and almost negligible quantity 
can be removed in this manner. Even if 
the strainer is made of fine sand, the re¬ 
sults are not satisfactory, except under 
certain conditions, chiefly because the 
greater part of the putrescible material is 
in solution and therefore goes through the 
strainer uncaught. 
Nature is always a wise teacher, and it 
needs but moderate observation to show 
that her method of getting rid of foul or¬ 
ganic matter is through the process of de¬ 
cay. No matter whether the waste 
material is animal, like dead bodies or 
manure, or is vegetable, like wood or 
apples, nature, if allowed, starts the 
process of decay immediately and, 
sooner or later, only dust remains to 
show how nature acts to keep her 
world pure and wholesome. Follow¬ 
ing this suggestion, sewage disposal 
should consist not only of the separa¬ 
tion of the solids from the polluted 
water, but also of the properly regu¬ 
lated decay of all the organic matter 
present, whether solid or liquid, so 
carried on that the process shall be as 
inoffensive as possible. 
For some years it has been known 
that decay is the result of the activity 
of certain bacteria and that their ac¬ 
tion is most energetic and effective 
wherever bacteria are best suited with 
surroundings. It is also known that 
in the soil, particularly in the surface 
layers, millions of the right kinds of 
bacteria are always to be found. Their 
activity depends both on the amount 
of organic matter present and on an 
abundance of air which must be sup¬ 
The ordinary construction of a septic tank. 
Both pipes are bent so that their openings 
are not clogged by the sediment or scum 
The intermittent flow chamber. The siphon regulates 
the liquid flowing during the day so that the cham¬ 
ber will discharge the right amount at intervals 
plied through the voids or pores of the soil. Thus in clay or 
peaty soils, with the inevitable absence of voids, no bacterial ac¬ 
tion is possible, because the essential air is lacking. 
When one attempts to make use of soil bacteria in purifying 
sewage, the difficulty arises that their action requires time, and 
it has been proved that pouring sewage continuously in large 
quantities through or onto a coarse sandy soil is a failure because 
the bacteria become overworked. They may even be drowned 
and the soil then becomes choked with a putrid mass. On the 
other hand, properly managed, with due reference to the needs 
of the bacteria, such a soil will not only 
strain out the solids, but will also effec¬ 
tually reduce the organic matter, both 
solids and liquids, to an inoffensive 
residue. 
Three essential conditions have been 
worked out by the aid of which sewage 
disposal on the soil becomes scientifically 
possible, and it has become equally estab¬ 
lished that only by the aid of the soil can 
sewage disposal be made practically suc¬ 
cessful. These three conditions are, first, 
a rate of application suitable to the soil 
available, and second, an interrupted or in¬ 
termittent delivery of the sewage so that 
the bacteria can, as it were, breathe be¬ 
tween the applications of liquid and, third, 
a resting period in which the process of 
decay is carried forward and perfected. 
There is, besides the pi'actical neces¬ 
sity of getting a large volume of water 
through the soil, a necessity which pre¬ 
vents the use of fine sand or silt as 
well as of clay and suggests the use 
of very coarse material. 
Taking up the question of rate of 
application, it has been found that a 
sandy soil in which the grains are all. 
as nearly as may be, of the same size 
and which contains no clay or fine 
dust makes the best sort of soil for 
treating sewage. On such soil, sew¬ 
age will be cared for without offense 
at the rate of ten gallons of sewage 
per square yard of surface, or, since 
each person of a family in which water 
is used freely requires about thirty 
gallons of water a day—most of which 
is converted into sewage—the soil area 
should be at the rate of three square 
yards to each person. A depth of 
about three feet is all that can be 
utilized, and if no suitable soil is avail¬ 
able an artificial sand bed can be made 
by hauling in sand until the proper 
area is provided. If the particles are 
made coarser, so that the liauid runs 
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