The process of water entering a water intake before treatment

Raw water intakes draw water from various specified levels in a river, lake, or reservoir behind a dam. In order to protect the pumps and remove large objects from the water before it enters the pumping station, strainers are usually installed in the intake structure. Aeration is a process unit that removes gases and volatile organic compounds that cause taste and odor problems in the water supply system. Aeration is also used to oxidize certain soluble metals and convert them to insoluble forms. This process unit may be located within the intake structure or just before the treatment plant.

Raw Water Intake Structures

Raw water intake structures use surface water sources to control the withdrawal of raw water. Their primary goal is to withdraw water of the best quality and free of fish, floating matter, coarse sediment, and other undesirable suspended matter. These structures may be a simple submerged pipe or a complex tower-like structure with gates, strainers, control valves, pumps, chemical injectors, flow meters, office buildings, and maintenance workshops. This unit may be part of the dam or a separate structure at another location.

Types of water intake structures

Several different types of water intakes, including floating, submerged, tower, shore and pier intakes, are used in water supply systems. The choice of one of these structures depends on the nature of the water source and the quantity and quality of the water to be abstracted.

Floating intakes

Floating intakes are a relatively inexpensive method of abstracting water from existing lakes or reservoirs. These structures are particularly suitable for water sources with unfavorable geological conditions and where there is little variation in water level over time. This type of intake has a boat-like structure that floats on the water surface and holds pumps, strainers, valves, electrical switches and other equipment. The entire structure is supported by at least two concrete or steel columns. These columns are designed to allow the intake to be moved based on changes in water level. The structure is connected to the shore by a bridge over which water intake pipes and electrical cables pass, providing access to the intake.

Submerged intakes

Submerged intakes are used to collect water from rivers or lakes where the water level changes little throughout the year. These intakes are constructed as troughs or cones equipped with a debris trap. These structures may consist of a simple concrete box or a wooden trough filled with rocks to protect the intake pipe. The intake pipe discharges water either into a well near the shore where pumping equipment is installed, or into a gravity transfer system. The open top of the intake is covered by steel bars or screens. In sources with high silt deposits, the open top of the intake is extended to a height of about 1-2 meters above the bottom.

Tower intakes

Tower intakes are often built in large water supply schemes and on rivers or reservoirs with severe water level fluctuations. These water intakes may be built near the shore or at a relatively distant distance from it, where they can only be accessed by boat. To enable the best quality water intake, valves are provided at different heights in the water intake. There are two types of water intake towers: wet water intake towers and dry water intake towers.

1_ Wet water intake towers

Wet water intake towers are circular concrete chambers filled with water, the water level in them is level with the water level in the source, and they have an internal well that is connected to the intake pipe. There are openings on the outer wall of the concrete chamber and the wall of the inner well to receive water. The openings in the wall of the inner well are equipped with valves to control the flow of water. The purpose of the outer chamber filled with water is to create sufficient weight to balance the buoyancy force when the inner well is dry.

2_ Dry intake towers

In a dry intake tower, water enters the well through openings equipped with valves. Due to the lack of an outer chamber filled with water, these intakes must be constructed in such a way that they can withstand buoyancy forces. The advantage of dry towers over the wet type is the possibility of water withdrawal from different heights by installing appropriate valves.

Shore intakes

Coastal intake structures are used in rivers and lakes with a relatively constant water level or lakes and reservoirs with deep shorelines. These intakes are usually concrete structures open to the water. The structures may be constructed in such a way that a pumping station can be located in them.

Pier intakes

Pier intake structures are built on rivers and lakes where the water depth at the shore is very shallow and the use of a shore intake is not possible. This unit is also used when it is necessary to build a water intake in an existing water source. Quay intake structures consist of a steel beam or concrete slab mounted on steel or concrete foundations. These slabs support pumps, pipes, valves, electrical switches, and other equipment. The quay is connected to the shore by a bridge that provides easy access to the intake and protects the intake pipes.

Selecting an Intake Site

Engineers must carefully consider many factors when locating raw water intakes. These factors include water quality, current or wave velocity, foundation stability, accessibility, availability of electrical power, proximity to a treatment plant, hazard to shipping, and environmental impacts.