Facilities for surface water intake
Complex structures, which serve to extract water from the source is called the water intake. Depending on the source water supply intake structures are distinguished:
According to the degree of stationarity of the intakes are divided into stationary and non-stationary (floating, travelling). By purpose are divided into technical and drinking. Duration of operation – permanent and temporary. Technological and design features – bucket, power, combined, etc. By location of receiving waters – coastal and bed. The required reliability of water supply in accordance with the instructions of SNiP II-31-74. The performance of small (less than 1 m 3 /h), medium (from 1 to 6 m 3 /h) and large (more than 6 m 3 /h).
The water source and the choice depends on local environmental conditions. Industrial enterprise generally uses surface water.
For a reliable choice of source of water supply devices and diversion structures should consider the following features of the reservoir:
A) security costs and levels;
B) the nature of the sediment;
In) stability of the channel;
G) the ice regime;
D) water quality.
Security costs and urovnevaja.
When designing water intake facilities should take into account the availability of design flows and water level in the reservoir.
The nature of the sediment.
The river water carries with it solid particles moving along the bottom and directly in the stream. When choosing a water intake facilities should take into account that entrained suspension along the bottom of the river, can bring water intake structure.
The stability of the riverbed.
The riverbed is constantly under the influence of river flow and different winding shape in plan. This form of the channel due to the blur ability in the most stable location of the riverbed.
The ice regime.
With the onset of cold at low water speeds, the surface layer of water cools and forms ice. At high speeds of water movement the formation of the ice cover difficult. In this case, the ice cover is preceded by the autumn break, accompanied by the formation of bottom (deep) of ice. It is formed by the supercooling of water. Fast flow of supercooled water is in a state of turbulent flow that lead to an intensive heat exchange between the surface and bottom layers. In contact with supercooled water layer with a solid surface of the river bottom is formed of bottom ice, which can reach thicknesses of 1.5 m.
The formation of bottom ice is preceded by the appearance of sludge, which can cover almost all the section of the river, and this in turn complicates the operation of water intake facilities. Effective action to reduce the sludge is the discharge of spent water in the receiving water, heated water vapor grates, replacement of metal grilles wood.
General technological scheme of water intake has two characteristic types: coastal and riverbed. They differ in the location of withdrawal point of water relative to the shore and can be performed on separate and combined scheme.
Satisfied with run-of-river intakes in the absence of sufficient depths, water pollution, or weak soils near the coast, the higher water temperature in this place. The scheme of separate intake channel type regardless of the type of water body includes: a flooded inlet with bars, siphon or gravity pipe, shore the water sump, pumping station first lift, the camera switching. Water through the inlet of the suction conduit enters into the receiving well. The water velocity in gravity lines are equal 1-1,5 km/h. On suction lines with a diameter up to 500 mm establish adoptive valves, with diameters over 500 mm the vacuum pumps. The velocity of the water at the suction pipe is taken equal to 1,2 -1,7 km/h.
The scheme intake channel shown in Fig. 2-1. This scheme is applicable to intakes with low productivity. At medium and large capacity intake used scheme that combines coastal sumps and suction chamber with pumping stations of the first lift.