FIG. 79.
Water Purification.
The impurities of water consist of two classes, insoluble and soluble. The former can be readily removed by processes of settling and filtration. For this purpose most paper-mills are provided with large ponds capable of holding several days’ supply. These are sometimes supplemented by filtering beds. Insoluble impurities can also be removed by passing the water through filter-presses.
Fig. 80 is an illustration of Rœckner’s patent clarifier, which may also be applied to this purpose.
The cylinders C dip below the surface of the water to be purified, which is contained in the reservoir A. They are open at their lower ends, but are closed at the top by the domes D. These are connected with the pump I by means of the pipes H. On starting the pump the water rises slowly in the cylinders. As soon as it reaches the level of the top, the action of the pump is stopped and the cocks K opened, when the water commences to flow down the pipes G, which together {212} with the cylinders form a kind of siphon. If the reservoir A be kept full, the siphons can be made to act continuously. The flow of water being slow, insoluble impurities have time to subside.
The impurities may from time to time be removed by means of the small pump L connected with the bottom of the reservoir.
The clarifier can also be used for the purification of the effluent water from paper-mills.
FIG. 80.