Transcriber Note
Text emphasis denoted by _Italics_ and =Bold=. Whole and fractional parts
of numbers as 123-4/5.
U. S. DEPARTMENT OF AGRICULTURE
FARMERS' BULLETIN No. 1227
SEWAGE AND SEWERAGE OF FARM HOMES
DISPOSAL OF FARM SEWAGE in a clean manner is always an important problem.
The aims of this bulletin are twofold--(1) to emphasize basic principles
of sanitation; (2) to give directions for constructing and operating home
sewerage works that shall be simple, serviceable, and safe.
Care in operating is absolutely necessary. No installation will run
itself. Continued neglect ends in failure of even the best-designed,
best-built plants. If the householder is to build and neglect, he might as
well save expense and continue the earlier practice.
Washington, D. C. Issued January, 1922
Revised October, 1928
SEWAGE AND SEWERAGE OF FARM HOMES
George M. Warren, Hydraulic Engineer, Bureau of Public Roads
CONTENTS
Page
Introduction 1
Sewage, sewers, and sewerage defined 1
Nature and quantity of sewage 2
Sewage-borne diseases and their avoidance 2
How sewage decomposes 5
Importance of air in treatment of sewage 7
Practical utilities 8
Septic tanks 21
Grease traps 43
General procedure 45
INTRODUCTION
The main purpose of home sewerage works is to get rid of sewage in such
way as (1) to guard against the transmission of disease germs through
drinking water, flies, or other means; (2) to avoid creating nuisance.
What is the best method and what the best outfit are questions not to be
answered offhand from afar. A treatment that is a success in one location
may be a failure in another. In every instance decision should be based
upon field data and full knowledge of the local needs and conditions.
An installation planned from assumed conditions may work harm. The
householder may be misled as to the purification and rely on a protection
that is not real. He may anticipate little or no odor and find a nuisance
has been created.
SEWAGE, SEWERS, AND SEWERAGE DEFINED
Human excrements (feces and urine) as found in closets and privy vaults
are known as night soil. These wastes may be flushed away with running
water, and there may be added the discharges from washbasins, bathtubs,
kitchen and slop sinks, laundry trays, washing vats, and floor drains.
This refuse liquid product is sewage, and the underground pipe which
conveys it is a sewer. Since sewers carry foul matter they should be
water-tight, and this feature of their construction distinguishes them
from drains removing relatively pure surface or ground water. Sewerage
refers to a system of sewers, including the pipes, tanks, disposal works,
and appurtenances.
NATURE AND QUANTITY OF SEWAGE
Under average conditions a man discharges daily about 3½ ounces of moist
feces and 40 ounces of urine, the total in a year approximating 992
pounds.[1] Feces consist largely of water and undigested or partially
digested food; by weight it is 77.2 per cent water.[2] Urine is about 96,3
per cent water.[2]
[1] Practical Physiological Chemistry, by Philip B. Hawk, 1916, pp. 221,
359.
[2] Agriculture, by P. H. Storer, 1894, vol. 2, p. 70.
The excrements constitute but a small part of ordinary sewage. In
addition to the excrements and the daily water consumption of perhaps
40 gallons per person are many substances entering into the economy of
the household, such as grease, fats, milk, bits of food, meat, fruit and
vegetables, tea and coffee grounds, paper, etc. This complex product
contains mineral, vegetable, and animal substances, both dissolved and
undissolved. It contains dead organic matter and living organisms in the
form of exceedingly minute vegetative cells (bacteria) and animal cells
(protozoa). These low forms of life are the active agents in destroying
dead organic matter.
The bacteria are numbered in billions and include many species, some
useful and others harmful. They may be termed tiny scavengers, which under
favorable conditions multiply with great rapidity, their useful work
being the oxidizing and nitrifying of dissolved organic matter and the
breaking down of complex organic solids to liquids and gases. Among the
myriads of bacteria are many of a virulent nature. These at any time may
include species which are the cause of well-known infectious and parasitic
diseases.
SEWAGE-BORNE DISEASES AND THEIR AVOIDANCE
Any spittoon, slop pail, sink drain, urinal, privy, cesspool, sewage
tank, or sewage distribution field is a potential danger. A bit of spit,
urine, or feces the size of a pin head may contain many hundred germs,
all invisible to the naked eye and each one capable of producing disease.
These discharges should be kept away from the food and drink of man
and animals. From specific germs that may be carried in sewage at any
time there may result typhoid fever, tuberculosis, cholera, dysentery,
diarrhea, and other dangerous ailments, and it is probable that other
maladies may be traced to human waste. From certain animal parasites or
their eggs that may be carried in sewage there may result intestinal
worms, of which the more common are the hookworm, roundworm, whipworm,
eelworm, tapeworm, and seat worm.
Sewage, drainage, or other impure water may contain also the causative
agents of numerous ailments common to livestock, such as tuberculosis,
foot-and-mouth disease, hog cholera, anthrax, glanders, and stomach and
intestinal worms.
Disease germs are carried by many agencies and unsuspectingly received by
devious routes into the human body. Infection may come from the swirling
dust of the railway roadbed, from contact with transitory or chronic
carriers of disease, from green truck grown in gardens fertilized with
night soil or sewage, from food prepared or touched by unclean hands
or visited by flies or vermin, from milk handled by sick or careless
dairymen, from milk cans and utensils washed with contaminated water, or
from cisterns, wells, springs, reservoirs, irrigation ditches, brooks,
or lakes receiving the surface wash or the underground drainage from
sewage-polluted soil.
Many recorded examples show with certainty how typhoid fever and other
diseases have been transmitted. A few indicating the responsibilities and
duties of people who live in the country are cited here.
In August, 1889, a sister and two brothers aged 18, 21, and 23 years,
respectively, and all apparently in robust health dwelt together in a
rural village in Columbiana County, Ohio. Typhoid fever in particular
virulent form developed after use of drinking water from a badly polluted
surface source. The deaths of all three occurred within a space of 10
days.
In September and October, 1899, 63 cases of typhoid fever, resulting
in 5 deaths, occurred at the Northampton (Mass.) insane hospital. This
epidemic was conclusively traced to celery, which was eaten freely in
August and was grown and banked in a plot that had been fertilized in the
late winter or early spring with the solid residue and scrapings from a
sewage filter bed situated on the hospital grounds.
Some years ago Dr. W. W. Skinner, Bureau of Chemistry, Department of
Agriculture, investigated the cause of an outbreak of typhoid fever in
southwest Virginia. A small stream meandered through a narrow valley
in which five 10-inch wells about 450 feet deep had been drilled in
limestone formation. The wells were from 50 to 400 feet from the stream,
from which, it was suspected, pollution was reaching the wells. In a pool
in the stream bed approximately one-fourth mile above the wells several
hundred pounds of common salt were dissolved. Four of the wells were cut
off from the pump and the fifth was subjected to heavy pumping. The water
discharged by the pump was examined at 15-minute intervals and its salt
content determined over a considerable period of time. After the lapse of
several 15-minute intervals the salt began to rise and continued to rise
until the maximum was approximately seven times that at the beginning of
the test, thus proving the facility with which pollution may pass a long
distance underground and reach deep wells.
Probably no epidemic in American history better illustrates the dire
results that may follow one thoughtless act than the outbreak of typhoid
fever at Plymouth, Pa., in 1885. In January and February of that year the
night discharges of one typhoid fever patient were thrown out upon the
snow near his home. These, carried by spring thaws into the public water
supply, caused an epidemic running from April to September. In a total
population of about 8,000, 1,104 persons were attacked by the disease and
114 died.
Like plants and animals, disease germs vary in their powers of resistance.
Some are hardy, others succumb easily. Outside the body most of them
probably die in a few days or weeks. It is never certain when such germs
may not lodge where the immediate surroundings are favorable to their life
and reproduction. Milk is one of the common substances in which germs
multiply rapidly. The experience at Northampton shows that typhoid-fever
germs may survive several months in garden soil. Laboratory tests by the
United States Public Health Service showed that typhoid-fever germs had
not all succumbed after being frozen in cream 74 days. (Public Health
Reports, Feb. 8, 1918, pp. 163-166.) Ravenel kept the spores of anthrax
immersed for 244 days in the strongest tanning fluids without perceptible
change in their vitality or virulence. (Annual Report, State Department of
Health, Mass., 1916, p. 494.)
=Unsafe practices.=--Upon thousands of small farms there are no privies
and excretions are deposited carelessly about the premises. A place of
this character is shown in figure 1. Upon thousands of other farms the
privy is so filthy and neglected that hired men and visitors seek near-by
sheds, fields, and woods. A privy of this character is shown in figure 2.
These practices and conditions exist in every section of the country. They
should be abolished.
[Illustration: Fig. 1.--One of many farms lacking the simplest sanitary
convenience]
Deserving of severe censure is the old custom of conveying excrements or
sewage into abandoned wells or some convenient stream. Such a practice is
indecent and unsafe. It is unnecessary and is contrary to the laws of most
of the States.
Likewise dangerous and even more disgusting is the old custom of using
human excrement or sewage for the fertilization of truck land. Under
no circumstances should such wastes be used on land devoted to celery,
lettuce, radishes, cucumbers, cabbages, tomatoes, melons, or other
vegetables, berries, or low-growing fruits that are eaten raw. Disease
germs or particles of soil containing such germs may adhere to the skins
of vegetables or fruits and infect the eater.
Upon farms it is necessary to dispose of excretal wastes at no great
distance from the dwelling. The ability and likelihood of flies carrying
disease germs direct to the dinner table, kitchen, or pantry are well
known. Vermin, household pets, poultry, and live stock may spread such
germs. For these reasons, and also on the score of odor, farm sewage never
should be exposed.
=Important safety measure.=--The farmer can do no other one thing so vital
to his own and the public health as to make sure of the continued purity
of the farm water supply. Investigations indicate that about three out of
four shallow wells are polluted badly.
Wells and springs are fed by ground water, which is merely natural
drainage. Drainage water usually moves with the slope of the land. It
always dissolves part of the mineral, vegetable, and animal matter of the
ground over or through which it moves. In this way impurities are carried
into the ground water and may reach distant wells or springs.
The great safeguards are clean ground and wide separation of the well
from probable channels of impure drainage water. It is not enough that
a well or spring is 50 or 150 feet from a source of filth or that it is
on higher ground. Given porous ground, a seamy ledge, or long-continued
pollution of one plat of land, the zone of contamination is likely to
extend long distances, particularly in downhill directions or when the
water is low through drought or heavy pumping. Only when the surface of
the water in a well or spring is at a higher level at all times than any
near-by source of filth is there assurance of safety from impure seepage.
Some of the foregoing facts are shown diagrammatically in Figure 3. Figure
4 is typical of those insanitary, poorly drained barnyards that are almost
certain to work injury to wells situated in or near them. Accumulations
of filth result in objectionable odor and noxious drainage. Figure 5
illustrates poor relative location of privy, cesspool, and well.
[Illustration: Fig. 2.--The rickety, uncomfortable, unspeakably foul,
dangerous ground privy. Neglected by the owner, shunned by the hired man,
avoided by the guest, who, in preference, goes to near-by fields or woods,
polluter of wells, meeting place of house flies and disease germs, privies
of this character abide only because of man's indifference]
Sewage or impure drainage water should never be discharged into or upon
ground draining toward a well, spring, or other source of water supply.
Neither should such wastes be discharged into openings in rock, an
abandoned well, nor a hole, cesspool, vault, or tank so located that
pollution can escape into water-bearing earth or rock. Whatever the system
of sewage disposal, it should be entirely and widely separated from the
water supply. Further information on locating and constructing wells is
given in Farmers' Bulletin 1448-F, Farmstead Water Supply, copies of which
may be had upon request to the Division of Publications, Department of
Agriculture.
Enough has been said to bring home to the reader these vital points:
1. Never allow the farm sewage or excrements, even in minutest quantity,
to reach the food or water of man or livestock.
2. Never expose such wastes so that they can be visited by flies or other
carriers of disease germs.
3. Never use such wastes to fertilize or irrigate vegetable gardens.
4. Never discharge or throw such wastes into a stream, pond, or abandoned
well, nor into a gutter, ditch, or tile drainage system, which naturally
must have outlet in some watercourse.
[Illustration: Fig. 3.--How an apparently good well may draw foul
drainage. Arrows show direction of ground water movement. _A-A_, Usual
water table (surface of free water in the ground); _B-B_, water table
lowered by drought and pumping from well _D_; _C-C_, water table further
lowered by drought and heavy pumping; _E-F_, level line from surface of
sewage in cesspool. Well _D_ is safe until the water table is lowered to
_E_; further lowering draws drainage from the cesspool and, with the water
table at _C-C_, from the barn. The location of well _G_ renders it unsafe
always]
[Illustration: Fig. 4.--An insanitary, poorly drained barnyard. (Board of
Health, Milwaukee.) Liquid manure or other foul drainage is sure to leach
into wells situated in or near barnyards of this character]
HOW SEWAGE DECOMPOSES
When a bottle of fresh sewage is kept in a warm room changes occur in the
appearance and nature of the liquid. At first it is light in appearance
and its odor is slight. It is well supplied with oxygen, since this gas
is always found in waters exposed to the atmosphere. In a few hours the
solids in the sewage separate mechanically according to their relative
weights; sediment collects at the bottom, and a greasy film covers the
surface. In a day's time there is an enormous development of bacteria,
which obtain their food supply from the dissolved carbonaceous and
nitrogenous matter. As long as free oxygen is present this action is
spoken of as aërobic decomposition. There is a gradual increase in the
amount of ammonia and a decrease of free oxygen. When the ammonia is near
the maximum and the free oxygen is exhausted the sewage is said to be
stale. Following exhaustion of the oxygen supply, bacterial life continues
profuse, but it gradually diminishes as a result of reduction of its food
supply and the poisonous effects of its own wastes. In the absence of
oxygen the bacterial action is spoken of as anaërobic decomposition. The
sewage turns darker and becomes more offensive. Suspended and settled
organic substances break apart or liquefy later, and various foul-smelling
gases are liberated. Sewage in this condition is known as septic and the
putrefaction that has taken place is called septicization. Most of the
odor eventually disappears, and a dark, insoluble, mosslike substance
remains as a deposit. Complete reduction of this deposit may require many
years.
[Illustration: Fig. 5.--Poor relative locations of privy, cesspool, and
well. (State Department of Health, Massachusetts.) Never allow privy,
cesspool, or sink drainage to escape into the plot of ground from which
the water supply comes]
IMPORTANCE OF AIR IN TREATMENT OF SEWAGE
Decomposition of organic matter by bacterial agency is not a complete
method of treating sewage, as will be shown later under "Septic tanks." It
is sufficient to observe here that in all practical methods of treatment
aeration plays a vital part. The air or the sewage, or both, must be in a
finely divided state, as when sewage percolates through the interstices
of a porous, air-filled soil. The principle involved was clearly stated
30 years ago by Hiram F. Mills, a member of the Massachusetts State Board
of Health. In discussing the intermittent filtration of sewage through
gravel stones too coarse to arrest even the coarsest particles in the
sewage Mr. Mills said: "The slow movement of the sewage in thin films over
the surface of the stones, with air in contact, caused a removal for some
months of 97 per cent of the organic nitrogenous matter, as well as 99 per
cent of the bacteria."
PRACTICAL UTILITIES
Previous discussion has dealt largely with basic principles of sanitation.
The construction and operation of simple utilities embodying some of
these principles are discussed in the following order: (1) Privies for
excrements only; (2) works for handling wastes where a supply of water is
available for flushing.
PIT PRIVY
Figure 6 shows a portable pit privy suitable for places of the character
of that shown in figure 1, where land is abundant and cheap, and in such
localities has proved practical. It provides, at minimum cost and with
least attention, a fixed place for depositing excretions where the filth
can not be tracked by man, spread by animals, reached by flies, nor washed
by rain.
[Illustration: Fig. 6.--Portable pit privy. For use where land is abundant
and cheap, but unless handled with judgment can not be regarded as safe.
The privy is mounted on runners for convenience in moving to new locations]
The privy is light and inexpensive and is placed over a pit in the ground.
When the pit becomes one-half or two-thirds full the privy is drawn or
carried to a new location. The pit should be shallow, preferably not
over 2½ feet in depth, and never should be located in wet ground or rock
formation or where the surface or the strata slope toward a well, spring,
or other source of domestic water supply. Besides standing on lower ground
the pit should never be within 200 feet of a well or spring. Since dryness
in the pit is essential, the ground should be raised slightly and 10 or
12 inches of earth should be banked and compacted against all sides to
shed rain water. The banking also serves to exclude flies. If the soil
is sandy or gravelly, the pit should be lined with boards or pales to
prevent caving. The standard galvanized or black enameled wire cloth
having 14 squares to the inch. The whole seat should be easily removable
for cleaning. A little loose absorbent soil should be added daily to the
accumulation in the pit, and when a pit is abandoned it should be filled
immediately with dry earth mounded to shed water.
A pit privy for use in field work, consisting of a framework of ½-inch
iron pipe for corner posts connected at the top with ¼-inch iron rods bent
at the ends to right angles and hung with curtains of unbleached muslin,
is described in Public Health Report of the United States Public Health
Service, July 26, 1918.
A pit privy, even if moved often, can not be regarded as safe. The danger
is that accumulations of waste may overtax the purifying capacity of the
soil and the teachings reach wells or springs. Sloping ground is not a
guaranty of safety; the great safeguard lies in locating the privy a long
distance from the water supply and as far below it as possible.
SANITARY PRIVY
The next step in evolution is the sanitary privy. Its construction must
be such that it is practically impossible for filth or germs to be spread
above ground, to escape by percolation underground, or to be accessible to
flies, vermin, chickens, or animals. Furthermore, it must be cared for in
a cleanly manner, else it ceases to be sanitary. To secure these desirable
ends sanitarians have devised numerous types of tight-receptacle privy.
Considering the small cost and the proved value of some of these types, it
is to be regretted that few are seen on American farms.
The container for a sanitary privy may be small--for example, a
galvanized-iron pail or garbage can, to be removed from time to time by
hand; it may be large, as a barrel or a metal tank mounted for moving;
or it may be a stationary underground metal tank or masonry vault. The
essential requirement in the receptacle is permanent water-tightness to
prevent pollution of soils and wells. Wooden pails or boxes, which warp
and leak, should not be used. Where a vault is used it should be shallow
to facilitate emptying and cleaning. Moreover, if the receptacle should
leak it is better that the escape of liquid should be in the top soil,
where air and bacterial life are most abundant.
Sanitary privies are classified according to the method used in treating
the excretions, as dry earth, chemical, etc.
DRY-EARTH PRIVY
=Pail type.=--A very serviceable pail privy is shown in Figures 7 and 8.
The method of ventilation is an adaptation of a system that has proved
very effective in barns and other buildings here and abroad. A flue with
a clear opening of 16 square inches rises from the rear of the seat and
terminates above the ridgepole in a cowl or small roofed housing. Attached
to this flue is a short auxiliary duct, 4 by 15 inches, for removing foul
air from the top of the privy. In its upper portion on the long sides the
cowl is open, allowing free movement of air across the top of the flue.
In addition, the long sides of the cowl are open below next to the roof.
These two openings, with the connecting vertical air passages, permit free
upward movement of air through the cowl, as indicated by the arrows. The
combined effect is to create draft from beneath the seat and from the top
of the privy. The ventilating flue is 2 by 8 inches at the seat and 4 by 4
inches 5 feet above. The taper slightly increases the labor of making the
flue, but permits a 2-inch reduction in the length of the building.
[Illustration: Fig. 7.--Pail privy. Well constructed, ventilated, and
screened. With proper care is sanitary and unobjectionable]
In plan the privy is 4 by 4½ feet. The sills are secured to durable posts
set about 4 feet in the ground. The boarding is tight, and all vents and
windows are screened to exclude insects. The screens may be the same as
for pit privies or, if a more lasting material is desired, bronze or
copper screening of 14 squares to the inch may be used. The entire seat
is hinged, thus permitting removal of the receptacle and facilitating
cleaning and washing the underside of the seat and the destruction of
spiders and other insects which thrive in dark, unclean places. The
receptacle is a heavy galvanized-iron garbage can. Heavy brown-paper bags
for lining the can may be had at slight cost, and their use helps to keep
the can clean and facilitates emptying. Painting with black asphaltum
serves a similar purpose and protects the can from rust. If the contents
are frozen, a little heat releases them. Of nonfreezing mixtures a strong
brine made with common salt or calcium chloride is effective. Two and
one-half to 3 pounds of either thoroughly dissolved in a gallon of water
lowers the freezing point of the mixture to about zero. Denatured alcohol
or wood alcohol in a 25 per cent solution has a like low freezing point
and the additional merit of being noncorrosive of metals. The can should
be emptied frequently and the contents completely buried in a thin layer
by a plow or in a shallow hand-dug trench at a point below and remote from
wells and springs. Wherever intestinal disease exists the contents of
the can should be destroyed by burning or made sterile before burial by
boiling or by incorporation with a strong chemical disinfectant.
[Illustration: Fig. 8.--Pail privy]
[Illustration: Fig. 9.--A well-ventilated privy in Montana]
A privy ventilated in the manner before described is shown in Figure 9.
The cowl, however, is open on four sides instead of two sides as shown
in Figures 7 and 8. The working drawings (figs. 7 and 8) show that the
construction of a privy of the kind is not difficult. Figure 10 gives
three suggestions whereby a privy may be conveniently located and the
approach screened or partially hidden by latticework, vines, or shrubbery.
=Vault type.=--A primitive and yet serviceable three-seat dry-earth privy
of the vault type is shown in Figure 11. This privy was constructed in
1817 upon a farm at Westboro, Mass. The vault, made of bricks, was 6 feet
long by 5 feet wide, and the bottom was 1 foot below the surface of the
ground. The brickwork was laid in mortar, and the part below the ground
surface was plastered on the inside. The outside of the vault was exposed
to light and air on all four sides. Across the long side of the vault
in the rear was a door swinging upward through which the night soil was
removed two or three times a year, usually in the spring, summer, and fall
and hauled to a near-by field, where it was deposited in a furrow, just
ahead of the plow.
Especial attention is called to the shallowness of the vault and the
lightened labor of cleaning it out. The swinging door at the rear
facilitated the sprinkling of dry soil or ashes over the contents of the
vault, thus avoiding the necessity of carrying dirt and dust into the
building and dust settling upon the seat. This privy was in use for nearly
100 years without renewal or repairs. When last seen the original seat,
which always was kept painted, showed no signs of decay. Modern methods
would call for a concrete vault of guaranteed water-tightness,[3] proper
ventilation and screening, and hinging the seat.
[3] Directions for mixing and placing concrete to secure water-tightness
are contained in Farmers' Bulletin 1279-F, "Plain concrete for farm use,"
and Farmers' Bulletin 1572-F, "Making Cellars Dry."
Working drawings for a very convenient well-built two-seat vault privy
are reproduced in Figures 12 and 13. The essential features are shown in
sufficient detail to require little explanation. With concrete mixtures of
1:2:3 (1 volume cement, 2 volumes sand, 3 volumes stone) for the vault and
1:2:4 for the posts there will be required a total of about 2 cubic yards
of concrete, taking 3½ barrels of cement, 1 cubic yard of sand, and 1½
cubic yards of broken stone or screened gravel. The stone or gravel should
not exceed 1 inch in diameter, except that a few cobblestones may be
embedded where the vault wall is thickest, thus effecting a slight saving
of materials.
[Illustration: Fig. 10.--Screening the approach to a privy. _A_, Raised
platform with lattice sides, suitable for short distances, convenient,
and easily cleared of snow; _B_, walk hidden by latticework; _C_, walk
inclosed by an arbor]
CHEMICAL CLOSET
[Illustration: Fig. 11.--A primitive vault privy in Massachusetts. Note
the tight, shallow, easily cleaned vault. _A_, Brick vault 5 by 6 feet,
bottom about 1 foot in the ground; _B_, water-tight plastering; _C_,
rowlock course of brick; _D_, door hinged at top; _E_, door button; _F_,
three-pane window hinged at top; _G_, passageway]
A type of sanitary privy in which the excrements are received directly
into a water-tight receptacle containing chemical disinfectant is meeting
with considerable favor for camps, parks, rural cottages, schools, hotels,
and railway stations. These chemical closets,[4] as they are called, are
made in different forms and are known by various trade names. In the
simplest form a sheet-metal receptacle is concealed in a small metal or
wooden cabinet, and the closet is operated usually in much the same manner
as the ordinary pail privy. These closets are very simple and compact,
of good appearance, and easy to install or move from place to place. In
another type, known as the chemical tank closet, the receptacle is a
steel tank fixed in position underground or in a basement. The tank has a
capacity of about 125 gallons per seat, is provided with a hand-operated
agitator to secure thorough mixing of the chemical and the excretions, and
the contents are bailed, pumped, or drained out from time to time.
[4] Among publications on chemical closets are the following: "Chemical
closets," Reprint No. 404 from the Public Health Reports, U. S. Public
Health Service, June 29, 1917, pp. 1017-1020: "The chemical closet,"
Engineering Bulletin No. 5, Mich. State Board of Health, October, 1916;
Health Bulletin, Va. Department of Health, March, 1917, PP. 214-219.
Chemical closets, like every form of privy, should be well installed,
cleanly operated, and frequently emptied, and the wastes should receive
safe burial. With the exception of frequency of emptying, the same can
be said of chemical tank closets. With both forms of closet thorough
ventilation or draft is essential, and this is obtained usually by
connecting the closet vent pipe to a chimney flue or extending it well
above the ridgepole of the building. The contents of the container should
always be submerged and very low temperatures guarded against.
[Illustration: Fig. 12.--Two-seat vault privy]
As to the germicidal results obtained in chemical closets, few data are
available. A disinfecting compound may not sterilize more than a thin
surface layer of the solid matter deposited. Experiments by Dr. Alvah
H. Doty with various agents recommended and widely used for the bedside
sterilization of feces showed "that at the end of 20 hours of exposure
to the disinfectant but one-eighth of an inch of the fecal mass was
disinfected."[5] Plainly, then, to destroy all bacterial and parasitic
life in chemical closets three things are necessary: (1) A very powerful
agent; (2) permeation of the fecal mass by the agent; (3) retention of
its strength and potency until permeation is complete. The compounds or
mixtures commonly used in chemical closets are of two general kinds:
First, those in which some coal-tar product or other oily disinfectant is
used to destroy germs and deodorize, leaving the solids little changed in
form; second, those of the caustic class that dissolve the solids, which,
if of sufficient strength and permeating every portion, should destroy
most if not all bacterial life. Not infrequently the chemical solution
is intended to accomplish disinfection, deodorization, and reduction to
a liquid or semiliquid state. Ordinary caustic soda, costing about $1 in
10-pound pails, has given good results.
[5] Annual Report, Mass. State Board of Health, 1914, p. 727.
A simple type of chemical closet is shown in Figure 14, and the essential
features are indicated in the notation. These closets with vent pipe and
appurtenances, ready for setting up, retail for $20 and upward. A chemical
tank closet, retailing for about $80 per seat, is shown in Figure 15.
The Department of Agriculture occasionally receives complaints from people
who have installed chemical closets, usually on the score of odors or the
cost of chemicals.
[Illustration: Fig. 13.--Two-seat-vault privy. Note the shallow,
water-tight, easily cleaned concrete vault]
DISINFECTANTS AND DEODORANTS
Disinfection is the destruction of disease germs. Sterilization is
the destruction of all germs or bacteria, both the harmful and the
useful. Antisepsis is the checking or restraining of bacterial growth.
Deodorization is the destruction of odor. Unfortunately in practice none
of these processes may be complete. The agent may be of inferior quality,
may have lost its potency, or may not reach all parts of the mass treated.
A disinfectant or germicide is an agent capable of destroying disease
germs; an antiseptic is an agent merely capable of arresting bacterial
growth, and it may be a dilute disinfectant; a deodorant is an agent that
tends to destroy odor, but whose action may consist in absorbing odor or
in masking the original odor with another more agreeable one.[6]
[6] Those desiring more explicit information on disinfectants and the
principles of disinfection are referred to U. S. Department of Agriculture
Farmers' Bulletin 926, "Some Common Disinfectants," and 954, "The
Disinfection of Stables." and to publications of the U. S. Public Health
Service.
Of active disinfecting agents, heat from fire, live steam, and boiling
water are the surest. The heat generated by the slaking of quicklime has
proved effective with small quantities of excreta. Results of tests by the
Massachusetts State Board of Health[7] show that the preferable method
consists in adding sufficient hot water (120° to 140° F.) to cover the
excrement in the receptacle, then adding small pieces of fresh strong
quicklime in amount equal to about one-third of the bulk of water and
excrement combined, covering the receptacle, and allowing it to stand 1½
hours or longer.
[7] Annual Report, Mass. State Board of Health, 1914, pp. 727-729.
[Illustration: Fig. 14.--Chemical closet. _A_, Water-tight sheet-metal
container; _B_, metal or wooden cabinet; _C_, wooden or composition seat
ring; _D_, hinged cover; _E_, 3 or 4 inch ventilating flue extending 18
inches above roof or to a chimney; _F_, air inlets]
[Illustration: Fig. 15.--Chemical tank closet. _A_, Tank, 2 feet 3 inches
by 4 feet 2 inches 5/64th-inch iron, seams welded; capacity, 125 gallons;
_B_, 14-inch covered opening for recharging and emptying tank; _C_,
12-inch galvanized sheet-metal tube; _D_, 4-inch sheet-metal ventilating
pipe extending above ridgepole or to a chimney; _E_, agitator or paddle]
Among chemical disinfectants a strong solution of sodium hydroxide
(caustic soda) or potassium hydroxide (caustic potash, lye) is very
effective and is useful in dissolving grease and other organic substances.
Both chemicals are costly, but caustic soda is less expensive than
caustic potash and constitutes most of the ordinary commercial lyes.
Chlorinated lime (chloride of lime, bleaching powder) either in solution
or in powdered form is valuable. For the disinfection of stools of
typhoid-fever patients the Virginia State Board of Health[8] recommends
thoroughly dissolving ½ pound of best chlorinated lime in 1 gallon of
water and allowing the solution to cover the feces for at least 1 hour.
The solution should be kept in well-stoppered bottles and used promptly,
certainly within 2 or 3 days. Copper sulphate (blue vitriol, bluestone)
in a 5 per cent solution (1 pound in 2½ gallons of water) is a good but
rather costly disinfectant. None of the formulas here given is to be
construed as fixed and precise. Conditions may vary the proportions, as
they always will vary the results. The reader should remember that few,
if any, chemical disinfectants can be expected fully to disinfect or
sterilize large masses of excrement unless the agent is used repeatedly
and in liberal quantities or mechanical means are employed to secure
thorough incorporation.
[8] Health Bulletin, Va. State Board of Health, June, 1917, pp. 277-280.
Among deodorants some of the drying powders mentioned below possess
more or less disinfecting power. Chlorinated lime, though giving off an
unpleasant odor of chlorine, is employed extensively. Lime in the form
of either quicklime or milk of lime (whitewash) is much used and is an
active disinfectant. To prepare milk of lime a small quantity of water is
slowly added to good fresh quicklime in lumps. As soon as the quicklime
is slaked a quantity of water, about four times the quantity of lime, is
added and stirred thoroughly. When used as a whitewash the milk of lime is
thinned as desired with water and kept well stirred. Liberal use of milk
of lime in a vault or cesspool, though it may not disinfect the contents,
is of use in checking bacterial growth and abating odor. To give the best
results it should be used frequently, beginning when the vault or cesspool
is empty. Iron sulphate (green vitriol, copperas) because of its affinity
for ammonia and sulphides is used as a temporary deodorizer in vaults,
cesspools, and drains; 1 pound dissolved in 4 gallons of water makes a
solution of suitable strength.
PREVENTION OF PRIVY NUISANCE
The following is a summary of simple measures for preventing a privy from
becoming a nuisance:
1. Locate the privy inconspicuously and detached from the dwelling.
2. Make the receptacle or vault small, shallow, easy of access, and
water-tight.
3. Clean out the vault often. Do not wait until excrement has accumulated
and decomposition is sufficiently advanced to cause strong and foul odors.
4. Sprinkle into the vault daily loose dry soil, ashes, lime, sawdust,
ground gypsum (land plaster), or powdered peat or charcoal. These will
absorb liquid and odor, though they may not destroy disease germs.
5. Make the privy house rain-proof; ventilate it thoroughly, and screen
all openings.
OBJECTION TO PRIVIES
All the methods of waste disposal heretofore described are open to the
following objections:
1. They do not take care of kitchen slops and liquid wastes incident to a
pressure water system.
2. They retain filth for a considerable period of time, with probability
of odors and liability of transmission of disease germs.
3. They require more personal attention and care than people generally are
willing to give.
By far the most satisfactory method yet devised of caring for sewage
calls for a supply of water and the flushing away of all wastes as soon
as created through a water-tight sewer to a place where they undergo
treatment and final disposal.
KITCHEN-SINK DRAINAGE
A necessity in every dwelling is effective disposal of the kitchen-sink
slops. This necessity ordinarily arises long before the farm home is
supplied with water under pressure and the conveniences that go with it.
Hence the first call for information on sewage disposal is likely to
relate merely to sink drainage. This waste water, though it may not be
as dangerous to health as sewage containing human excrements, is still a
menace to the farm well and capable of creating disagreeable odor.
[Illustration: Fig. 16.--How to waste kitchen-sink drainage. _A_, Sink;
_B_, waste pipe; _C_, trap; _D_, clean-out; _E_, box filled with hay,
straw, sawdust, excelsior, coke, or other insulating material; _F_, 4-inch
vitrified sewer-pipe, hubs uphill, and joints made water tight for at
least 100 feet downhill from a well; _G_, 4-inch vitrified sewer pipe,
hubs downhill, joints slightly open, laid in an 18-inch bed of coarse
sand, gravel, stone, broken brick, slag, cinders, or coke; _H_, strip
of tarred paper on burlap or a thin layer of hay, straw, cornstalks,
brush, or sods, grass side down; _I_, 12 inches of natural soil; _J_,
stone-filled pit. As here illustrated, water is drawn by a pitcher or
kitchen pump (_K_) through a 1¼ or 1½ inch galvanized-iron suction pipe
(_L_) from a cistern (_M_). The suction pipe should be laid below frost
and on a smooth upward grade from cistern to pump and be provided with a
foot valve (_N_) to keep the pump primed. If a foot valve is used, pump
and pipe must be safe from frost or other means than tripping the pump be
provided for draining the system]
The usual method of disposing of sink slops is to allow them to dribble
on or beneath the surface of the ground close to the house. Such drainage
should be taken in a water-tight carrier at least 100 feet downhill from
the well and discharged below the surface of the ground. Every sink should
be provided with a suitable screen to keep all large particles out of the
waste pipe. An approved form of sink strainer consists of a brass plate
bolted in position over the outlet and having at least 37 perforations not
larger than one-fourth inch in diameter. Provided a sink is thus equipped
and is given proper care and the land has fair slope and drainage,
the waste water may be conducted away through a water-tight sewer and
distributed in the soil by means of a short blind drain. A simple
installation, consisting of a kitchen-sink and pump and means of disposal
as described, is shown in Figure 16.
CESSPOOLS
Where farms have water under pressure an open or leaching cesspool is a
common method of disposing of the sewage. Ordinary cesspools are circular
excavations in the ground, lined with stone or brick laid without mortar.
They vary from 5 to 10 feet in diameter and from 7 to 12 feet in depth.
Sometimes the top is arched and capped at the ground surface by a cover of
wood, stone, or cast-iron. At other times the walls are carried straight
up and boards or planks are laid across for a cover, and the entire
structure is hidden with a hedge or shrubbery.
Except under the most favorable conditions the construction and use of
a cesspool can not be condemned too strongly. They are only permissible
where no other arrangement is possible. Leaching cesspools especially are
open to these serious objections:
1. Unless located in porous soil, stagnation is likely to occur, and
failure of the liquid to seep away may result in overflow on the Surface
of the ground and the creation of a nuisance and a menace.
2. They retain a mass of filth in a decomposing condition deep in the
ground, where it is but slightly affected by the bacteria and air of
the soil. In seeping through the ground it may be strained, but there
can be no assurance that the foul liquid, with little improvement in
its condition, may not pass into the ground water and pollute wells and
springs situated long distances away in the direction of underground flow.
For the purpose of avoiding soil and ground-water pollution cesspools have
been made of water-tight construction and the contents removed by bailing
or pumping. Upon the farm, however, this type of construction has little
to recommend it, for the reason that facilities for removing and disposing
of the contents in a clean manner are lacking.
In some instances cesspools have been made water-tight, the outflow being
effected by three or four elbows or =T=-branches set in the masonry near
the top, with the inner ends turned down below the water surface, the
whole surrounded to a thickness of several feet with stone or gravel
intended to act as a filtering medium. Tests of the soil water adjacent to
cesspools of this type show that no reliance should be placed upon them as
a means of purifying sewage, the fatal defects being constant saturation
with sewage and lack of air supply. To the extent that the submerged
outlets keep back grease and solid matters the scheme is of service in
preventing clogging of the pores of the surrounding ground.
Where the ground about a cesspool has become clogged and water-logged,
relief is often secured by laying several lines of drain tile at shallow
depth, radiating from the cesspool. The ends of the pipes within the
cesspool should turn down, and it is advantageous to surround the lines
of pipe with stones or coarse gravel, as shown in Figure 16 and discussed
under "Septic tanks." In this way not only is the area of percolation
extended, but aeration and partial purification of the sewage are effected.
Where a cesspool is located at a distance from a dwelling and there is
opportunity to lead a vent pipe up the side of a shed, barn, or any stable
object it is advisable to do so for purposes of ventilation. Where the
conditions are less favorable it may be best, because of the odor, to omit
any direct vent pipe from the cesspool and rely for ventilation on the
house sewer and main soil stack extending above the roof of the house.
Cesspools should be emptied and cleaned at least once a year and the
contents given safe burial or, with the requisite permission, wasted in
some municipal sewerage system. After cleaning, the walls and bottom may
be treated with a disinfectant or a deodorant.
SEPTIC TANKS
A tight, underground septic tank with shallow distribution of the effluent
in porous soil generally is the safest and least troublesome method of
treating sewage upon the farm, while at the same time more or less of the
irrigating and manurial value of the sewage may be realized.
The late Professor Kinnicutt used to say that a septic tank is "simply a
cesspool, regulated and controlled." The reactions described under the
captions "How sewage decomposes" and "Cesspools" take place in septic
tanks.
In all sewage tanks, whatever their size and shape, a portion of the solid
matter, especially if the sewage contains much grease, floats as scum on
the liquid, the heavier solids settle to form sludge, while finely divided
solids and matter in a state of emulsion are held in suspension. If the
sludge is retained in the bottom of the tank and converted or partly
converted into liquids and gases, the tank is called a septic tank and the
process is known as septicization. The process is sometimes spoken of as
one of digestion or rotting.
=History.=--Prototypes of the septic tank were known in Europe nearly 50
years ago. Between 1876 and 1393 a number of closed tanks with submerged
inlets and outlets embodying the principle of storage of sewage and
liquefaction of the solids were built in the United States and Canada. It
was later seen that many of the early claims for the septic process were
extravagant. In recent years septic tanks have been used mainly in small
installations, or, where employed in large installations, the form has
been modified to secure digestion of the sludge in a separate compartment,
thus in a measure obviating disadvantages that exist where septicization
takes place in the presence of the entering fresh sewage.
=Purposes.=--The purposes of a septic tank are to receive all the farm
sewage, as defined on page 1, hold it in a quiet state for a time, thus
causing partial settlement of the solids, and by nature's processes of
decomposition insure, as fully as may be, the destruction of the organic
matter.
=Limitations.=--That a septic tank is a complete method of sewage
treatment is a widespread but wrong impression. A septic tank does not
eliminate odor and does not destroy all organic solids. On the contrary,
foul odors developed, and of all the suspended matter in the sewage about
one-third escapes with the effluent, about one-third remains in the tank,
and about one-third only is destroyed or reduced to liquids and gases.
The effluent is foul and dangerous. It may contain even more bacteria
than the raw sewage, since the process involves intensive growths. As
to the effects upon the growth and virulence of disease germs little is
known definitely. It is not believed that such germs multiply under the
conditions prevailing in a septic tank. If disease germs are present, many
of their number along with other bacteria may pass through with the flow
or may be enmeshed in the settling solids and there survive a long time.
Hence the farmer should safeguard wells and springs from the seepage or
discharges from a septic tank as carefully as from those of cesspools.