Practical preventive medicine . be from 40 to 50 gallons, in largecities from 100 to 200 gallons. Per capita its average composi-tion will be about the following: Average daily water consumption 285,000 gms. Fecal solids 100 gms. Urinary solids 50 gms. Miscellaneous solids 500 gms. From the standpoint of its composition we may considersewage to be a more or less homogenous suspension of fineparticles with organic and mineral matter in solution. Theorganic matter present is very unstable so that its chemicalcomposition is variable, depending on the age of the organic constitu
Practical preventive medicine . be from 40 to 50 gallons, in largecities from 100 to 200 gallons. Per capita its average composi-tion will be about the following: Average daily water consumption 285,000 gms. Fecal solids 100 gms. Urinary solids 50 gms. Miscellaneous solids 500 gms. From the standpoint of its composition we may considersewage to be a more or less homogenous suspension of fineparticles with organic and mineral matter in solution. Theorganic matter present is very unstable so that its chemicalcomposition is variable, depending on the age of the organic constituents are urea, albumen, fibrin, casein, io6 PRACTICAL PREVENTIVE MEDICINE starch, sugar, fats, and soaps. Of the elemental substancespresent nitrogen and sulphur are of the greatest importance. 4. Sewage Disposal by Dilution.—The large volume of waterpresent demands that economical transportation be effectedby gravity, and that it be discharged into some convenientwater course. The discharge of the untreated sewage into some. Fig. 11.—Diagram illustrating self-purification in the Thames, discharge of the large volume of sewage from London soon markedly lowersthe dissolved oxygen, which however is restored by the time the water reachesthe rivers estuary. (U. S. Geological Survey, W. S. Paper 185.) water course is known as disposal by dilution. It has givenrise to a series of problems, arising from nuisances and thecontamination of public water supplies, from which havedeveloped the modern methods of sewage treatment and waterpurification. If the body of water into which the raw sewage is dischargedis of sufficient volume, disposal by dilution may be sufficient. EXCRETA DISPOSAL 107. On the other hand, if the diluting body is of insufficient volume,or if drinking water supplies are contaminated, or oyster bedsare contaminated, or a nuisance is produced, it is unsatisfac-tory or even dangerous. When the process is satisfactory the following events takeplace: (a) Th
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