Note 257 — Chapter XXVI · PUBLIC HEALTH AND SANITATION
Reading edition
The choice between the two kinds of filtration depends upon local conditions. Where the raw water is excessively turbid or bad-colored, the rapid sand filter is more commonly used. The chemical treatment of water involves the use of chlorinated lime (better known as bleaching powder) or some other chemical disinfectant which kills the noxious bacteria. Only small quantities are required in proportion to the volume of water used. Chemical treatment is not commonly used except in emergencies; it is not regarded as a satisfactory permanent plan of water treatment.