The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks.
- James Lane-Notter
- Date:
- 1900
Licence: In copyright
Credit: The theory and practice of hygiene (Notter and Firth) / by J. Lane Notter ... and W. H. Horrocks. Source: Wellcome Collection.
Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.
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![Capacity of Subsidence Reservoir. Filters. Thickness of Sand in Filters. Monthly Kate of Fil- tration per square foot per hour, 1898. Names of Companies. ] UUDIC L/UIlutjUuD. dumber of Days' Supply. Area. Area per million gallons of Average Daily Supply. Maxi- mum. Mini- mum. Mean Monthly Averages. Maximum Monthly Averages. Chelsea, 140,000,000 11-8 acres. 8 acres. 0-67 ft. in. 4 3 ft. in. 6 0 gallons. 1 -TPi I 1 0 gallons. 1-75 East London, 1,215,000,000 31-0 31 0-79 2 6 1 6 111 i oo Grand Junction, . 64,000,000 3-2 1-22 3 0 1 6 1-61 1-86 Lambeth, . 128,000,000 5-1 m 0-48 3 0 2 6 2-03 2-50 New River, 168,100,000 4-5 16i 0-45 2 3 1 7 2-43 2-75 Southwark and 436,000,000 13-3 0-61 3 0 2 3 1-50 1-50 Vauxhall, West Middlesex,. j 397,500,000 18-6 19 0-89 2 9 2 6 1-36 1-50 Action of a Filter-bed.-Tieike was the first to show that sand alone could not rimove micro-organisms from water; filters made of sterihsed sand were found to actuau/increase the number o bacteria during the firs few dlvs of working, but with the formation of a slimy layer on the surface Z the Ldy of the filter-bed, the true filtering action commenced. Sit sHmy layerf to which the greatest importance is now attached, consis of zooXa of bacteria combined with suspended materials m ^'^^er ; is extr°emely friable and readUy broken by excessive pressure on the surface or distrbance of the body of the filter-beds. Hence the extreme care now ri fn SwL filter beds from below so as to prevent the zoogloea masses ^ brok n by l^^e p^^^^^^^^^^^^ air, and to control the rate of filtration and St the pressure of water on the surface. The degi-ee of fineness and uniformTty^ o^^^^^^ sand grains are also of importance m securing a good Zate Bv nsina fine sand the current of water which passes through a Ss reni^red slow and uniform and the walls of the lacunar spaces are bea IS , ■ molecular action to take place and giving greater EeTtt W^noSs'layl Hence the work of a filte.bed is partly BTftlT-wtfof'tateria iu the W food ,Baterial is used up and ijy wie eliminated which have a powerful efi^ect m L'restin. tt o tt^ia U.rough the filter, It must not he supposed sand liter wm arrest au tv. S dXo rptSmpostd:,srs; ... up^r system which arrested sistea oi uwu oup i ^ fnrmed bv the inferior layers of the bed, lircr^iufd: r^a&high^ to^ materials At was thought inferior system and ^ad n^ t^^^^^^^^^^ ^^^^ ^ ^^^^ ,1^, Lawience expeni i ^^^^^^^^ ^^^^^^ g^^^^^^ filtration, then evtn i^^dJr fSlScTr^m cannot give absolute protect on agauis Tter toe disease; but if the rate of filtration is properly controlled, it can](https://iiif.wellcomecollection.org/image/b2135764x_0072.jp2/full/800%2C/0/default.jpg)
