MUNICIPAL WATER-WORKS LABORATORIES. 179 



In 1893 Mr. Edmund B. Weston, C. E., of Providence, R. I., con- 

 ducted for the water department of that city a series of experiments 

 upon the purification of the water of the Pawtuxet River by means of 

 mechanical filters. Though less extensive than the experiments above 

 mentioned, they are of historic interest as giving the first adequate dem- 

 onstration of the possibilities of that method of purification. 



The system of mechanical filtration, or the 'American System,' as it 

 is sometimes called, differs from natural sand filtration by the use of 

 alum or some similar coagulating substance before sedimentation and 

 filtration, by the higher rate of filtration employed and by the use of 

 certain mechanical devices for cleaning the sand beds. The application 

 of this process to the treatment of turbid water was next investigated. 

 In 1895 the Louisville Water Company undertook a most extensive 

 series of experiments to determine the relative efficiency of various 

 types of mechanical filters in the purification of the water of the Ohio 

 River. The w T ork was placed in charge of Mr. Geo. W. Fuller, C. E., who 

 was assisted by a large corps of trained assistants. For nearly a year 

 the experiments were earned on without interruption: the filters were 

 operated by the companies interested in them, and their efficiency was 

 determined by Mr. Fuller on behalf of the water company, who had at 

 hand a complete laboratory equipment and who used every means 

 known to science in the analysis of the water before and after treatment. 

 The most important result of these experiments was to prove beyond 

 doubt the applicability of mechanical filtration to the purification of 

 water rendered turbid by the presence of fine particles of clay. 



The experiments in Louisville were followed in 1898-9 by a some- 

 what similar investigation at Cincinnati, 0., also conducted by Mr. 

 Puller. As in Louisville, the water supply is taken from the Ohio River, 

 but the character of the water at this point is not in all respects the 

 same as that farther down stream. The problem in Cincinnati was to 

 determine wdiether the English system of sand filtration or the Ameri- 

 can system, involving the use of a coagulant, was best suited to the puri- 

 fication of the water, and whether any preliminary treatment of the 

 water before filtration was advisable. To solve this problem the Board 

 of Trustees, Commissioners of Water Works, decided to appropriate for 

 needed experiments a sum equivalent to about one year's interest on the 

 probable cost of a plant for filtering the supply of the city. The equip- 

 ment consisted of four steel tanks, each with a capacity of 100,000 gal- 

 lons, fifteen experimental filters, arranged for operation under different 

 conditions, and a large laboratory fully equipped for chemical and bac- 

 teriological work. After a period of continuous operation, covering 

 about ten months, the evidence showed that either the American system 

 or the English system operated with preliminary coagulation and sedi- 

 mentation would satisfactorily purify the water, but that the American 



