Fig. 121d.
| O = outfall sewer. | S = screen chamber. |
| D = detritus tank. | T = settlement tank. |
| C = carrier. | P = supply pipe. |
| F = filter. | E = effluent channel. |
| H = humus tank. | |
Dosing Apparatus.—Various methods of providing intermittent supply are in use. Among these one of the first was a simple form of balanced valve with float. This, however, has been superseded by other types, among which the syphons are the simplest form. One of the first of this type specially designed for the purpose in question was the low-draught syphon, manufactured by Messrs. Adams Hydraulics, Ltd., and shown in [Fig. 122]. The special feature of this apparatus is that it can be arranged for a small depth of sewage in the dosing tank. It will work with any depth from 6 inches upwards. These syphons can also be arranged to work singly, in pairs, each one coming into action alternately, or in numbers of three and upwards, when they can be adjusted to work in sequence or simultaneously.
Fig. 122.—Low-draught Dosing Syphon.
Another type of syphonic dosing apparatus is that supplied by the Patent Automatic Sewage Distributors, Ltd., and shown in [Fig. 123]. In this case a syphon is combined with a mechanical valve operated by floats, hence the name “auto-mechanical syphon.”
A further type of syphonic dosing apparatus is manufactured by Messrs. George Jennings, Ltd., as shown in [Fig. 124]. These syphons are arranged to work in regular sequence, and are operated by means of air valves, which are shown mounted on a frame and connected by means of air pipes to the syphons. The sequence is obtained by means of cams, fixed in different positions on a shaft, which is rotated by means of a float actuated by the rise and fall of the liquid in the dosing tank.