FILTER FOR INDUSTRIAL WORKS.
As a rule, bleach and dye works are established where there is a sufficiency of good and soft water, except in such cases where for special reasons it is desirable to use town water, and which then is generally clear. Where, however, water from brooks, rivers, or lodges is used, as is mostly the case, it is often discolored after heavy showers by earthy substances which are carried away by it. These impurities, all existing in the water in suspension, are not at all desirable for the dyer, and less for the bleacher, who generally allows the water to settle in a lodge, to give it time to deposit its impurities by gravitation. We understand that by means such as these even the water of the much-abused Irwell is made, in a Salford bleach-works, to produce some of the most beautiful whites possible. These lodges occupy, however, much space, which is not always available, and filtration is therefore the best where it can be carried out. We here produce the description of a cheap and efficient filter which bleachers or dyers may easily make for themselves. The dimensions are of course dependent upon the quantity of water to be filtered, and as a guide we shall describe a filter serving for a volume of water of about 1½ cubic yards per minute. In the first instance a hole is dug at a point where the water has sufficient fall to give it a head, and here a cistern set in cement is bricked out, measuring about 30 yards in length, 2½ yards in width, and 2½ yards in height. Across this cistern two partition walls are erected, one at the left resting upon rails, and the other going down to the bottom of the cistern. Between these two walls railway rails are laid crosswise, and over these a floor of wooden laths. Over this floor the filtering media are placed, consisting of a bottom layer of stones, then a layer of coke, then a layer of gravel, and lastly of a top layer of river sand. The water enters on the left-hand side into the space between the outer wall and the partition, and descends under the floor of the filter, through which it rises and passes in succession through the four layers of filtering substance until it issues at the top, when it runs over the partition, and out by the pipe shown in the right hand corner. It will be seen that the course of the water is upward through the filter, and in this respect contrary to the usual custom. The filter is cleaned about once a month by reversing the course of the water, and turning it indirectly on the top of the filter—causing it to run but at the bottom—and thus carrying all deposits with it. Both the central filtering compartments, as also the overflow cistern at the right hand, contain, near the bottom, doors, through which, when opened, the cleansing water runs off by a separate channel to the river. The dimensions of the cistern can, of course, be made to suit the situation.—Tex. Manfr.