Page:The New International Encyclopædia 1st ed. v. 18.djvu/32

SEWAGE. 18 George Thiuliolium, with a filter bed consisting of 3feet inilepthof foke, brol<en to small fragments. In 1891 Sidney I.owcock constructed a novel sewage purification plant for a private residence at Ashstead, England, in which he embodied, prob- ably for the first time, the principle that the bac- terial treatment of sewage invohed two distinct stages: the breaking down of the solid organic matter, or liquefaction, followed by nitrification. For the first stage he employed a closed tank, filled with broken stone. The sewage rose up- ward through this tank, then passed down through a series of nine perforated trays, each containing a thin bed of coke. The object of so many trays was to secure a more minute sub- division of bacterial labor. It is too early to say what rate of filtration will prove feasible with bacteria beds, but it seems doubtful whether the 500,000 to 1,000,000 gallons or more per acre, claimed in England, can be practical for a series of years without either poor results or large outlays for replacing clogged filtering material. The Septic Tank is designed to provide the first stage of bacterial action, mentioned just above, without the intervention of filtering ma- terial. The sewage first enters a small grit chamber, where sand and like heavy matter is speedily deposited on account of its relatively great weight. The sewage then goes on to a nar- row and rather long and shallow tank, having a trapped inlet and outlet, the better to exclude the air. The bulk of the suspended organic mat- ter is deposited and retained in this tank. The anaerobic bacteria seize upon and break up the sludge, which is transformed into dissolved and gaseous matter. The former passes out with the tank effluent. As any sludge left behind remains in the tank week after week, there is no lack of opportunity for complete bacterial reduction. The sludge accunuilates by slow degrees. The tank effluent, as has been stated, is about as w'ell puri- fied as that from chemical precipitation tanks, but it is in far better condition for further treat- ment, while the sludge problem has been prac- tically eliminated. Where further treatment is required to prevent water pollution the tank effluent is generally passed through bacteria beds, sometimes being preceded by aeration in order to establish more favorable conditions for the aerobic bacteria. The septic tank system was put in use at Exeter, England, in August, 1896, by Mr. Don- ald Cameron, town surveyor. Since then many other septic tanks have been built. The Exeter tank, like others built under Mr. Cameron's pat- ents, was tightly covered to exclude air and light. Covering, however, does not seem necessary. It is asserted that the septic tank was de- veloped independently at Urbana, 111., in 1894, by Professor A. N. Talbot. Certainly he built a tank there and then, which acted in much the same way as the septic tank. In 1895 he de- signed a more pretentious one for Champaign, 111., which was built in 1897. See Metcalf, "Anteced- ents of the Septic Tank," Proceedings of the Amer- ican Society of Civil Enfiineers (New York, 1901). Manufacturing Wastes may generally be dis- charged into town sewers. Occasionally they are of such a character as to demand separate treat- ment. Or the conditions may be such that proper treatment will result in the recovery of some product of commercial value. Much information SEWAGE. on the subject will be found in the reports of the Massachusetts State Board of Health. Houses Not Connected witk Sewers. .Al- though, as now understood, sewage is limited to those household and industrial wastes which are removed by sewers, it will be convenient to con- sider, in addition, the disposal of excrementitious matters and fouled water from such houses and other buildings as are not connected with tlie sewers. In rural districts this is generally a simple matter. Privy vaults, whether adjoining or more or less remote from houses, are generally little more than holes in the ground, into which the wastes fall and where they remain until re- moved at frequent intervals. The occasional addition of small quantities of dry earth or ashes will do nuich to lessen the almost inevitable nuisances of these devices. The comfort and ease of the family demand that such conveniences be placed as near the living rooms as possible, and ijreferably under the same roof; while in densely populated districts the latter is impera- tive. "herever decency and a due regard for health prevail this leads to the adoption of some portable receptacle, which can be kept in a sani- tary condition. The two chief means employed to meet this demand are the earth-closet and the pail system. The former is said to have been invented in 1858, by the Rev. Henry Moule. Vicar of Fordington, England. He utilized the deodor- izing powers of common soil and devised a mechanism for automatically dumping some of it into the closet when needed, somewhat on the same principle as the flushing arrangement for a water-closet. In the earth-closet a bucket, or some larger receptacle, may be used for the re- ception and removal of w-astes. The pail system is liot nuich different from the earth-closet, ex- cept that no earth or other deodorizer is neces- sarily used. The pails should be made of metal, or some other non-absorbent material. Tight- fitting covers should be provided. With the in- troduction of the water-closet, with its flushing tank and its pipe for the removal of wastes from the houses, a new problem arose in the way of final disposal. If no cesspool had been provided for sink and bath wastes, one was built .some- where in the yard. These, also, are generally mere holes in the ground, walled up roughly to prevent the caving in of the earth, but not made water-tight. In sandy soils the liquid soaks away. The solid matters are decomposed in the manner explained in the paragraph on septic tanks. In clayey or wet soils cesspools are sure to overflow. Theoretically all cesspools should be water-tight, but practically only a very few are. The contents of earth-closets may be utilized as fertilizing material with but little difficulty, either by composting or by direct application to the land. The utilization of pail-system wastes is not so easy, since they contain a large per- centage of moisture. An absorbent may be used to reduce the moisture, or the pails may be emp- tied where their contents can drain out. Still another way is to reduce the stuflT to a powder in some form of drier. Occasionally night soil from the pail system, and possibly from privies, is burned in garbage furnaces, care being taken to mix it with the driest material available. One of the best means of disposing of all night soil and allied matter is to bury it in trenches. Bibliography. Rafter and Baker, Sewage Disposal in the United States (New York, 1893),