SEWERAGE (OF. seurriere, canal, from ML. exuquatorium, drainage-canal, from Lat. ex, out + aqua, water) AND DRAINAGE (from AS. drehman, dreahnian, drenian, to drain, from AS., Goth. drayait, to draw, 01l(. frugal?, Ger. tragen, to carry). The removal and disposal of liquid and water-borne solid household wastes, the free ing of towns and vales from surface water, and the lowering and removal of subsoil water.
The two fundamental principles in the design of sewerage systems are (11 the removal of sew age before offensive decomposition sets in, which may be effected by providing sewers of ample capacity, uniform and sufficient slope, and smooth interiors; and (2) the disposal of sewage in such a manner that neither water, soil, nor air will be polluted thereby. Sewerage systems are gen erally divided into two portions: the collecting sewers and appurtenances and the outfall sewer or sewers. In addition there may be disposal works, including either a pumping or a purifica tion plant, or both. The aim always is so to design the collecting and outfall sewers that the discharge may be by gravity, thus avoiding the expense of a pumping plant.
Sewerage systems, as 110W understood, date chiefly from the middle of the nineteenth cen tury. A few ancient cities had sewers for the removal of fouled liquids, as well as for drain age. The most notable instance of this was Rome. (See CsoAcA.) But the Roman sewerage system did not serve the whole population. by any means. The drainage of London was the subject of legislation as early as 1225, but down to 1815 it was a penal offense to discharge ex crement or other offensive matter into the drains of that city. In 1847 the first act was passed making it compulsory to drain London houses into the sewers, and in 1859 work was begun on a system of intercepting sewers and storage tanks to cut of the discharge of sewage into the Thames within the city.
Paris had drains prior to 1536, but in 1663 their total length is said to have been only about six miles, of which one and one-half miles were closed and the remainder open channels. In 1820
Paris made the use of cesspools obligatory, but permitted the liquid overflow to be discharged into the sewers. 111 1880 a move was made to permit the discharge of all house sewage into the sewers, but up to the close of 1893, or just before the full adoption of the sewerage plan, of 266.044 houses in the city, only 10.934 were di rectly connected with the sewerage system.
In the United States, Boston had drains as early as 1701. After the adoption of a city charter in 1823 Boston assumed the ownership and control of all the drains and sewers which had been built by private parties. The date on which the sewers were opened for the reception of water-closet matter generally is not available: but presumably it followed shortly after the introduction of an ample public water supply, in 18-18.
It may he said of all cities that a sanitary sewerage system, as now conceived, is out of the question until a copious water supply has been provided. In most of the larger cities provisions for surface drainage preceded the introduction of sanitary sewers. Convenience gradually led to the use of these surface or storm sewers for the disposal of liquid, and then of solid house wastes, the connections for the latter purpose often being surreptitious at first. As public water supplies were introduced and the per capita water con sumption greatly increased, the disposal of the water thus brought into the houses often became even more serious a matter than the removal of surface and ground drainage. This led to the construction of sewers on the combined plan. The expense involved in building sewers large enough to carry off the rainfall was almost or quite prohibitive for all but the larger, closely built cities, so as the need for house sewerage systems increased sewers were built more and more frequently for this purpose alone.