A manual of hygiene and sanitation . Glass model of Loomls-Manning filter, showing filter in action. several days. Stone filters may be good, and resemblethe porcelain ones in action, but are apt to be slow and MATERIALS USED AS FILTERING MEDIA, 203 must be cleansed often. Sharp, clean sand, not too fine,has fair filtering properties, as it arrests most of the sus- FiG. Glass model of Loomis-Mannlng filter, showing self-scouriug of material during cleansing. pended matters and bacteria, beside oxidizing somewhatthe dissolved organic matters. It makes a good first layer 204 WATER. for a fi
A manual of hygiene and sanitation . Glass model of Loomls-Manning filter, showing filter in action. several days. Stone filters may be good, and resemblethe porcelain ones in action, but are apt to be slow and MATERIALS USED AS FILTERING MEDIA, 203 must be cleansed often. Sharp, clean sand, not too fine,has fair filtering properties, as it arrests most of the sus- FiG. Glass model of Loomis-Mannlng filter, showing self-scouriug of material during cleansing. pended matters and bacteria, beside oxidizing somewhatthe dissolved organic matters. It makes a good first layer 204 WATER. for a filter, because it is cheap and can be easily renewedor else readily cleansed and sterilized by boiling. Crushedquartz is of practically the same nature. Animal charcoal is, when fresh, an excellent material,as it removes both suspended and dissolved matters,organic and inorganic, and even color. It acts bothmechanically and chemically, and with a good volume ofit, water may pass through rapidly and be well after a time it ceases to be effective, nor must waterbe left too long in contact with it, as it will give uporganic matter to the water again and also calcium phos-phate, the latter especially favoring the development ofmicro-organisms. Moreover, fresh organic matter, andpossibly bacteria, are said to pass through it readily,though dead or decomposing
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecthygiene, bookyear1903
