دراسة لاستصلاح الاراضى الصحراوية الساحلية(4)

Pumping station
Pumping stations are facilities including pumps and equipment for pumping fluids from one place to another. They are used for a variety of infrastructuresystems, such as the supply of water to canals, the drainage of low-lying land, and the removal of sewage to processing sites.
A pumping station is, by definition, an integral part of a Pumped-storage hydroelectricity installation.
]Canal water supply
In countries with canal systems, pumping stations are also frequent. Because of the way the system of canal locks work, water is lost from the upper part of a canal each time a vessel passes through. Also, most lock gates are not watertight, so some water leaks from the higher levels of the canal to those lower down. Obviously, the water has to be replaced or eventually the upper levels of the canal would not hold enough water to be navigable.
Canals are usually fed by diverting water from streams and rivers into the upper parts of the canal, but if no suitable source is available, a pumping station can be used to maintain the water level. An excellent example of a canal pumping station is the Claverton Pumping Station on the Kennet and Avon Canal in southern England, United Kingdom. This pumps water from the nearby River Avon to the canal using pumps driven by the power of the river itself.
Where no external water supply is available, back pumping systems may be employed. Water is extracted from the canal below the lowest lock of a flight and is pumped back to the top of the flight, ready for the next boat to pass through. Such installations are usually very small.
[edit]Land drainage


: Metairie Pumping Station, also known as Pumping Station 6, building, constructed in 1899, near Metairie Road and the head of the17th Street Canal. Now housing 15Wood Screw Pumps, it can move over 6 billion gallons of water a day.
When low lying areas of land are drained, the general method is to dig drainage ditches. However, if the area is below sea level then it is necessary to pump the water upwards into water channels that finally drain into the sea.
The Victorians understood this concept, and in the United Kingdom they built pumping stations with water pumps, powered by steam engines to accomplish this task. In Lincolnshire, large areas of wetland at sea level, called The Fens, were turned into rich arable farmland by this method. The land is full of nutrients because of the accumulation of sedimentary mud that created the land initially.
Elsewhere, pumping stations are used to remove water that has found its way into low-lying areas as a result of leakage or flooding (in New Orleans, for example).
[edit]Package pumping station
In more recent times, a 'package pumping station' provides an efficient and economic way of installing a drainage system. They are suitable for mechanical building services collection and pumping of liquids like surface water, wastewater or sewage from areas where drainage by gravity is not possible.
A package pumping station is an integrated system, built in a housing manufactured from strong, impact-resistant polyethylene or glass-reinforced plastic. The unit is supplied with internal pipework fitted, pre-assembled ready for installation into the ground, after which the submersible pumps and control equipment are fitted. Features may include controls for fully automatic operation; a high-level alarm indication, in the event of pump failure; and possibly a guide-rail/auto-coupling/pedestal system, to permit easy removal of pumps for maintenance.
Compared to the conventional alternative of a concrete well and separate pump system, a packaged system offers the potential for reducing the cost and time involved with civil work and site labour.
]Sewerage systems
Pumping stations in sewage collection systems, also called lift stations, are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are laid at an angle so that a liquid can flow in one direction under gravity). Sewage is fed into and stored in an underground pit, commonly known as a wet well. The well is equipped with electrical instrumentation to detect the level of sewage present. When the sewage level rises to a predetermined point, a pump will be started to lift the sewage upward through a pressurized pipe system called a sewer force main from where the sewage is discharged into a gravity manhole. From here the cycle starts all over again until the sewage reaches its point of destination – usually a treatment plant. By this method, pumping stations are used to move waste to higher elevations. In the case of high sewage flows into the well (for example during peak flow periods and wet weather) additional pumps will be used. If this is insufficient, or in the case of failure of the pumping station, a backup in the sewer system can occur, leading to a sanitary sewer overflow – the discharge of raw sewage into the environment.
Sewage pumping stations are typically designed so that one pump or one set of pumps will handle normal peak flow conditions. Redundancy is built into the system so that in the event that any one pump is out of service, the remaining pump or pumps will handle the designed flow. The storage volume of the wet well between the 'pump on' and 'pump off' settings is designed to minimize pump starts and stops, but is not so long a retention time as to allow the sewage in the wet well to go septic.
The interior of a sewage pump station is a very dangerous place. Poisonous gases such as methane and hydrogen sulfide can accumulate in the wet well; an ill-equipped person entering the well would be overcome by fumes very quickly. Any entry into the wet well requires the correct confined space entry method for a hazardous environment. To minimize the need for entry, the facility is normally designed to allow pumps and other equipment to be removed from outside the wet well.
]Pumped-storage schemes
Main article: Pumped-storage hydroelectricity
A pumped-storage scheme is a type of power station for storing and producing electricity to supply high peak demands by moving water between reservoirs at different elevations.
Typically, water is channelled from a high-level reservoir to a low-level reservoir, through turbine generators that generate electricity. This is done when the station is required to generate power. During low-demand periods, such as overnight, the generators are reversed to become pumps that move the water back up to the top reservoir.
[left]