File:Hygiene, dental and general (1920) (14758352366).jpg

Identifier: hygienedentalge00turn (find matches)
Title: Hygiene, dental and general
Year: 1920 (1920s)
Authors: Turner, C. E. (Clair Elsmere), 1890-1974 Rice, William
Subjects: Hygiene Teeth
Publisher: St. Louis, C. V. Mosby
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ats Sludge Sludge duced. This process results in the reduction of the quantity ofsolids but leaves a residue or sludge which is tarry in consis-tency and appearance and is further putrescible. The abovechart contrasts the anaerobic and aerobic processes. 1. The Cesspool.—A familiar example of the anaerobicpurification of sewage is the leaching cesspool which is usuallybuilt like a well with sides made of large stones between whichthe water may pass into the surrounding soil. The sewagesolids accumulate at the bottom of this tank and are greatlyreduced in volume by the septic action of bacteria. 2. The Septic Tank.—Sometimes a tank with tight cementwalls is used instead of the leaching cesspool and here there 252 HYGIENE : DENTAL AND GENERAL is an even better opportunity for anaerobic action to take place.Here as in the old style cesspool the quantity of solids isgreatly reduced but residue must be occasionally removed.Large septic tanks are used in the purification of city sewage.
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Fig. 40.—Imhoff Tank. The water flows through the upper chamhers of thetank A and B, the flow being reduced by the baffles G; the upper chamber is sepa-rated from the lower or sludge digestion chamber C, by the partition F; the solidssettle out through the slot J, and the gases escape to the right D, being separatedfrom the fresh sewage. (Public Health Bulletin No. 101.) 3. The Two-story Tank.—More recently this simple tankhas been improved upon and we have had what we call thetwo-story tank of which perhaps the most important type isthat known as the Imhoff Tank. The sewage flows slowlythrough the upper chamber and the solids settle to the bottom WASTE DISPOSAL 253 and pass through, the narrow slot into the lower or sludgedigestion chamber. It is in the lower chamber that the septicprocess takes place and there is an advantage over the singlestory tank in that the gases produced are prevented from pass-ing through the fresh sewage. The result is that the effluentof such a tank ha

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