The conclusions reached as a result of this work have been of much value in the development of this type of filter and established the fundamental principles underlying the art. In general, it was shown that turbid waters could be saccessfully clarified and purified by this process, but preliminary subsidence with the assistance of coagulants was essential, and that longer per-lods for settlement than had previously been employed were necessary in order to obtain efficient results from the filters. The efficiency jot the experimental filters in removing bacteria ranged from 97.5 to 98.5 per cent. when operating under proper conditions.
Further experiments to clarify and purify the Ohio River were carried out at Cincinnati early in 1897. This work was undertaken by the City of Cincinnati through its Commissioners of Waterworks, who were about to build a new waterworks system including a purim fication plant.
In this experimental work, ample sedimentation periods were obtained in large settling tanks with preliminary coagulation of the settled water preceding filtration. Experiments were made both with rapid sand filters and clow sand filters. The main conclusion reached by those in charge of the experiments was that both the slow sand filters and rapid filters were able to produce a water of satisfactory quality, but that the method with rapid sand filters was the more economical,
Text read from the printed page and cleaned; old type leaves the occasional error.