Sewage Disposal Works: Their Design and Construction

by William Charles Easdale

In [Fig. 23] a somewhat similar arrangement is shown, but instead of Tee junctions the inlets and outlets are formed of easy bends, which may be in cast-iron or glazed stone ware as indicated. The observations made above in connection with [Fig. 22] apply generally to [Fig. 23].

[Fig. 24] is a plan of [Fig. 23], to show a number of inlets and outlets to one tank.

In [Fig. 25] the trapped inlet and outlet is formed by means of a cross wall carried up to the top of the tank with openings at the floor level in the form of arches. It is considered by some engineers that this method is a more substantial form of construction, and that it assists to a great extent in spreading the flow of the sewage over the whole area of the tank.

In [Fig. 26] both the inlet and outlet is in the form of a weir, running the full width of the tank, and it is probable that this is the most efficient means of ensuring that the flow of sewage shall spread over the whole area of the tank. The trapping of the inlet and outlet in this case is obtained by the use of scum boards or plates, as shown. When more than one tank of this type is required, it becomes necessary to provide a separate feed channel or carrier in addition to the channel immediately in front of the inlet weir, in order to arrange means for shutting one or more tanks out of work when required.

Fig. 25.

The method of arranging the inlets and outlets shown in [Fig. 27], consists of constructing extra deep sewage carriers and tank effluent channels, and making the connections from these to the tank at the desired depth below the top water level in the tank. It is true that these deep channels always stand full of sewage or tank effluent while the tank is in operation, but it is assumed that the passage into the tank of all solid matters in suspension is facilitated, especially during the minimum flow of sewage. It is essential that both channels should be well dished towards the tank on either side, so as to avoid all corners where solids may lodge, and render it easy to clean out the channels when the tank is emptied.