The amount of refuse and garbage in cities is quite considerable; in Manhattan, alone, the dry refuse amounts to 1,000,000 tons a year, and that of garbage to 175,000 tons per year. A large percentage of the dry refuse and garbage is valuable from a commercial standpoint, and could be utilized, with proper facilities for collection and separation. The disposal of refuse and garbage has not as yet been satisfactorily dealt with. The modes of waste disposal in the United States are: (1) dumping into the sea; (2) filling in made land, or plowing into lands; (3) cremation and (4) reduction by various processes, and the products utilized.
Sewage.—By sewage we mean the waste and effete human matter and excreta—the urine and fæces of human beings and the urine of domestic animals (the fæces of horses, etc., has great commercial value, and is usually collected separately and disposed of for fertilizing purposes).
The amount of excreta per person has been estimated (Frankland) as 3 ounces of solid and 40 ounces of fluid per day, or about 30 tons of solid and 100,000 gallons of fluid for each 1,000 persons per year.
In sparsely populated districts the removal and ultimate disposal of sewage presents no difficulties; it is returned to the soil, which, as we know, is capable of purifying, disintegrating, and assimilating quite a large amount of organic matter. But when the number of inhabitants to the square mile increases, and the population becomes as dense as it is in some towns and cities, the disposal of the human waste products becomes a question of vast importance, and the proper, as well as the immediate and final, disposal of sewage becomes a serious sanitary problem.
It is evident that sewage must be removed in a thorough manner, otherwise it would endanger the lives and health of the people.
The dangers of sewage to health are:
(1) From its offensive odors, which, while not always directly dangerous to health, often produce headaches, nausea, etc.
(2) The organic matter contained in sewage decomposes and eliminates gases and other products of decomposition.
(3) Sewage may contain a large number of pathogenic bacteria (typhoid, dysentery, cholera, etc.).
(4) Contamination of the soil, ground water, and air by percolation of sewage.