A TYPICAL FILTER PLANT 



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St. Louis, for example, is typical of many cities that per- 

 form marvels in transforming muddy river water into clear, 

 healthful drinking water. The Missouri-Mississippi water 

 as it enters the St. Louis intake contains mud and sand in 

 suspension; coloring matter from decaying leaves, as well 



ST. Louis FILTER PLANT 

 This building of reinforced concrete is 750 feet long by 135 feet wide. 



as mineral matter, in solution; and disease bacteria. As 

 the water passes slowly through settling tanks the heavier 

 sediment falls to the bottom of the tanks. Chemicals are 

 added. Some of these unite with the coloring matter, and 

 others with some of the mineral matter, forming chemical 

 compounds that are not soluble in water. These compounds 

 may fall to the bottom of settling tanks or may be removed 



