CHAPTER XXX. 

 SEWAGE AND SEWAGE DISPOSAL. 



MAN early learned that both esthetic and sanitary reasons 

 demand that sewage be properly treated. In the early history 

 of the race and also of a district the pit or trench was used for the 

 disposal of the refuse. Later this was lined with stone, brick 

 or cement to partly prevent diffusion into the surrounding soil, 

 and hence the contamination of the well. This, when properly 

 covered, became the cesspool which is largely in use in the rural 

 districts today. As population increased with its constantly 

 growing volume of human waste the old methods became inade- 

 quate, and hence there has developed the modern sewage system. 



Source, Composition and Quantity of Sewage. A city's sewage 

 consists of the public water supply carrying human and animal 

 'excreta, refuse from the kitchen, laundry, manufacturing estab- 

 lishments and the dust and dirt of the streets. Its quantity is 

 directly proportional to the consumption of water in the district. 

 In small cities it may be as low as forty or fifty gallons per capita 

 daily, whereas in larger cities it may reach from 100 to 200 gallons 

 or over. 



Its composition depends upon the density of population, the 

 number and kinds of manufacturing establishments, and whether 

 there is a separate or combined system. Where the combined 

 system is used the composition and quantity of the sewage varies 

 with the rainfall and street washing. There is also a diminution 

 in quantity and composition at night. 



Fuller gives the estimated amount of dry suspended solids in 

 the New York City sewage per 1000 inhabitants annually as 

 follows: 



Tons per 1000 



Inhabitants 

 Material. annually. 



Feces . . 14 



Toilet paper and newspaper 8 



Soap and washings 11 



Street wastes 8 



Miscellaneous 4 



Total ...."............ 45 



From the viewpoint of purification sewage contains proteins, 

 carbohydrates, fats, soaps, urea and other organic substances. 



