Hill, H: Rainfall, Water Supply, Waterways of the United Sta

Excerpt from Rainfall, Water Supply, Waterways of the United States

When water is made to ¿ow through a layer of sodium permutit, the latter exchanges its soda for the calcium and magnesium salts of the water and the degree of hardness in the latter is reduced to zero. The permutit has to be regenerated as it grows lax in action. This is easily accomplished by washing it for a few hours with a solution of common salt. Man ganese permutit in connection with marble dust removes all iron and acids from waters thus affected.

The practice of softening the entire water supply of a municipality has grown steadily and in not a few large manufacturing cities the municipal softening plant is saving the citi zens hundreds of thousands of tons of coal per annum and adding years of life to the community's boilers. The principal require ments are (1) mixing chambers, in which the softening chemicals are thoroughly mixed with the water; (2) capacious settling basins suffi cient to give the necessary time for the slower reactions when the temperature is low, as in winter; (3) a device for adding a coagulant (alum or ferrous sulphate) at both the en trance port and the exit port of the water into and from the settling basins, (4) substantial mechanical filters. In addition, as one of the requisites should be a special apparatus to slake the lime, reduce it to a proper emulsion and feed it in proper quantity automatically into the ¿owing water.

At the municipal water softening plant at Cleveland, Ohio, 000 gallons of water per day require the daily application of 40 tons of quicklime. This is slaked with hot water, mixed into an emulsion in an agitator, taken to tanks where it is cooled and diluted to the proper consistency and finally pumped at a uniform rate into the ¿owing water.

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