. The sanitation of cities. :~, o X Ji ^- ^ t^ -a 56 CHAPTER V THE SEWERAGE SYSTEM Three different plans or classes of sewerage sys-tems are in general use. Of late the newly de-signed intercepting sewers which carry the out-fall to a new point of final discharge have cometo be called the main drainage. The method ofsewage treatment required by a city dependsvery largely on the design, extent, and class ofsewerage systems installed. Each of these sys-tems may be briefly considered, as follows: The Combined System In this system all kinds of sewage and drain-age are carried in the same sewers.
. The sanitation of cities. :~, o X Ji ^- ^ t^ -a 56 CHAPTER V THE SEWERAGE SYSTEM Three different plans or classes of sewerage sys-tems are in general use. Of late the newly de-signed intercepting sewers which carry the out-fall to a new point of final discharge have cometo be called the main drainage. The method ofsewage treatment required by a city dependsvery largely on the design, extent, and class ofsewerage systems installed. Each of these sys-tems may be briefly considered, as follows: The Combined System In this system all kinds of sewage and drain-age are carried in the same sewers. There is ordi-narily but one sewer in each street, and to this thestreet inlets or basins are connected to admit thestorm waters, as well as the house sewer connec-tions, which admit all domestic wastes, roofwater, yard water, etc. In this system the outfall mains are of suffi-cient size to take care of the vast quantity ofstorm water when it rains; consequently they are 57. 58 ^be Sewerage System so large that in dry weather they act as setthngtanks, and delay the velocity of the domestic ordry weather flow sewage—which causes deposi-tion of solids in the sewer inverts. The solidsthus deposited remain, and decompose until astorm flow flushes them out. With this system,the sewage in dry weather loosens much sus-pended matter during its passage through thesewers, and the storm flow is rendered exceed-ingly heavy with decomposing sewage solidswhich are gathered up from the inverts duringthe first part of a storm. Combined and Intercepting System This system is similar to the foregoing system;in that all of the smaller sewers are combinedsewers; but to obviate the trouble caused by thedry weather, or domestic flow, in the large mains,and prevent the deposits therein of sewage solids,intercepting sewers are provided to collect thedry weather sewage from the smaller sewers, andact to some extent as separate sewers, parallelingthe lines of the large mains. Th
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Keywords: ., bookcentury1900, bookdecade1920, bookidcu3192400497, bookyear1921
