Intake Towers
Definition
Intake towers are huge structures of various designs standing in river and hence should be located so as not to interfere with navigation. Intake tower are generally used on large projects and on rivers or reservoirs where there are large fluctuation of water level. Gate controlled opening at various level called ports are generally provided in these concrete towers, which may helps in regulating the flow through the towers and permit some selection of the quality of water to be withdrawn.
Types of Intake Towers
1) Wet Intake Tower
A typical section of a wet intake tower is shown in below figure. It may consist of a concrete circular shell filled with water up to the reservoir level and has a vertical inside shaft which is connect to the withdrawal pipe. The withdrawal may be taken directly to the treatment plant in case no lift is required (such as in a reservoir) or to sump well in case a low lift is required (such as in a river). The withdrawal conduits may lie over the bed of the rivers or may be in the form of tunnels below the river bed. Opening are made into the outer concrete shell, as well as, into the inside shaft of as shown.
Gate are usually placed on the shaft so as to control the flow of water into the shaft and the withdrawal conduit. The water coming out of the withdrawal conduit may be taken to pump house for lift if the city's water treatment plant is located at high elevation; or may be taken directly to the treatment plant if it is situated at lower elevation.
2) Dry Intake Tower
The essential difference between a dry and wet intake tower is that, whereas in wet intake tower, the water enters from the entry ports into the tower and it enters into the conduit pipe through separate gate controlled opening; in a dry intake tower, the water is directly drawn into the withdrawal conduit through the gated entry ports as shown in figure.
A dry intake tower will, therefore have no water inside the tower if its gate are closed, whereas the wet intake tower will be full of water even if its gates are closed. When the entry ports are closed, a dry intake tower will be subjected to additional buoyant forces and hence, must be of heavier construction that wet intake towers. However, the dry intake towers are useful and beneficial in the sense that water can be withdrawn from any selected level of reservoir by opening the port at that level.
Differentiate Between Dry and Wet intake towers
Dry Intake Tower
1) Water is directly drawn into the withdrawal conduit through the gated entry ports.
2) It has no water inside the tower if its gates are closed.
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