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[2] 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.
[2] This subject is discussed at length in Technical Bulletin 675,
Sewage Irrigation as Practiced in the Western States.