SEWAGE and
GARBAGE
DISPOSAL
on the
FARM
FARMERS' BULLETIN No. 1950
U.S. DEPARTMENT OF AGRICULTURE
T
T HIS Bulletin is a guide to up to-date methods for the sanitary disposal of sewage and other household and farm wastes. It tells how to construct satisfactory sanitary facilities and how to maintain them and gives special attention to the questions on sanitation asked most frequently by farm people.
Solutions to all problems cannot be given here, and often advice must be sought from local sanitary officials. Many county and State health departments furnish advice and copies of local regulations and sometimes provide inspection service. Where there are no specific local requirements, this bulletin may be accepted as a guide to safe practice.
| Issued March 1944 |
| Washington, D. C. | Revised June 1946 |
SEWAGE AND GARBAGE DISPOSAL
ON THE FARM
By J. W. Rockey , assistant agricultural engineer, and J. W. Simons , associate agricultural engineer, Division of Farm Buildings and Rural Housing, Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration
The senior author prepared the preliminary draft, and the junior author completed the bulletin.
Contents
| Page |
| Characteristics of sewage |
| Protection of water sources from household wastes |
| Septic-tank systems |
| Operation of a septic tank system |
| Selecting the site |
| The house sewer |
| The septic tank |
| Building a concrete tank |
| The effluent sewer |
| The disposal field |
| Disposal methods in tight or wet soils |
| Care and maintenance of septic tanks |
| Effect of drain solvents and other materials |
| Protection against freezing |
| Septic-tank troubles |
| Grease traps |
| Disposal of drainage from fixtures other than toilets |
| Cesspools |
| Privies |
| Care, and maintenance |
| Chemical closets |
| Disposal of garbage and trash |
TO INSURE healthful living, domestic wastes must be disposed of. Primitive wanderers and too often present-day tourists deposit their wastes promiscuously and move on when the surroundings become foul. This is impractical in built-up communities. Therefore, in most cities and in some rural areas sanitary codes regulate the disposal of wastes.
CHARACTERISTICS OF SEWAGE
Household sewage ordinarily consists principally of human excrement, toilet paper, garbage, dish water, and other wash water from the various plumbing fixtures and floor drains.
Many kinds of bacteria, at times disease-producing ones, are contained in the discharges from the human body. Epidemics of typhoid fever, dysentery, diarrhea, cholera, and other water-borne diseases may result from the pollution of the water supply with sewage. Pollution is carried by water moving underground, as well as by water flowing on the surface. This is especially true in limestone regions, where underground channels and rock crevices permit water to flow for considerable distances with little filtering action. Sewage used for fertilizing or irrigating crops may contaminate vegetables or the udders of cows and thus spread disease. Anthrax, cholera, and parasitic worms may be present in the surface drainage from fields and barn lots. It is wise to regard all sewage as dangerous and to dispose of it promptly in a sanitary manner, so that disease germs will not pollute the water supplies or be spread by flies, animals, or man.
This subject is discussed at length in Technical Bulletin 675, Sewage Irrigation as Practiced in the Western States.
PROTECTION OF WATER SOURCES FROM HOUSEHOLD WASTES
Under most farm conditions a safe place for the disposal of wastes is in the upper 3-foot layer of soil, where the action of bacteria tends to render it harmless. Tile disposal fields, such as are used with septic tanks, and earth-pit privies accomplish this if the water table remains several feet below the surface and if the location is remote from water supplies. Cesspools and other types of pits do not ordinarily confine contamination to their immediate vicinity and are not recommended except for special conditions.
Sewage or other wastes discharged into abandoned wells or other pits that reach to the water table or below it are almost certain to contaminate the ground water.
It is generally poor practice, and often illegal, to discharge wastes into surface streams. Streams do not necessarily purify themselves in 50 feet, 100 feet, or some other stated distance, as is commonly believed. They do tend to purify themselves over long distances through the action of sunlight, aeration, and other factors but may not be safe for domestic use for many miles below the source of pollution. Clear, sparkling water is not always safe drinking water. Streams in agricultural communities are subject to many sources of pollution and they are likely to become more contaminated as they merge into larger streams.
SEPTIC-TANK SYSTEMS
Septic-tank systems, if installed and maintained properly, provide the most sanitary method of sewage disposal for farmhouses equipped with running water.
Ground water or rock close to the surface, lack of sufficient fall for the sewage to flow by gravity, and too small an absorption area for the effluent limit the satisfactory operation of a septic tank. When these conditions exist, special advice should be sought from a competent local sanitary authority. Adverse soil conditions can be overcome if sufficient fall and space are available.
The five essential parts () is added. To facilitate inspection and repairs it is good practice to keep in the house a chart showing the location of the tank and other parts of the system.
A septic tank does not necessarily purify the sewage, eliminate odor, or destroy all solid matter. Its purpose is to condition the sewage or domestic waste by bacterial action, so that it can be disposed of in a more satisfactory manner.
Figure 1. A septic-tank system.
OPERATION OF A SEPTIC-TANK SYSTEM
In a septic-tank system the sewage flows by gravity from the farmhouse through the sewer into the tank, where it should remain at least 24 hours. While passing through the tank the solids are acted upon by anaerobic bacteria, which work only in the dark and where there is little air. The heavy particles settle to the bottom as sludge, the lighter particles float as scum, and the remainder passes out of the tank through the effluent sewer to the disposal field. The gas released in the process escapes through a vent provided either in the T to the house sewer or the effluent sewer.
A tank that is too small may fill up with solids in a short while, because sufficient time is not allowed for breaking them down by fermentation, or the sewage may be pushed right through into the disposal field and clog it.
The effluent may contain even more disease germs than the original sewage, and though it may be as clear as spring water it is far from pure and may cause foul odors if discharged or allowed to pool on the surface of the ground.
The final disposition of the effluent into the upper layer of the soil exposes it to the action of aerobic bacteria. These bacteria, unlike those in the tank, need air and cannot work in saturated soil or live much more than 3 feet below the surface of the ground. The "living earth," or upper stratum, teems with these bacteria, which convert the dangerous sewage and disease germs into harmless matter and thus tend to purify the effluent if it remains long enough in the top layers of soil before seeping into the subsoil and thence to the ground water. Effluent discharged deep in the soil does not receive the benefit of this purifying action.
