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عمران::
intake آب دریا
The type of ocean biota that is affected by the construction and operation of a seawater intake is a function of the intake's location, the nature of the source water body, the local flora and fauna, and the design and operating characteristics of the intake�
Most circulating water systems employ some type of primary screening device (bar rack) to block larger objects from entering the seawater intake system� Smaller secondary screening systems generally consist of an array of mesh or slot screens that can be stationary or rotating� Mesh sizes of approximately 0�95 cm (3⁄8 in�) to 1�6 cm (5⁄8 in�) are commonly used in the steam electric power industry to screen cooling water intake structures� Fish and other aquatic organisms large enough to be blocked by these screens may become impinged if the intake velocity exceeds their ability to move away, or if they become entangled in debris that may be present in front of the intake system� These organisms will remain impinged against the screens until the intake velocity is reduced so they can move away or until the screen is rotated and backwashed to remove them
Relatively few seawater intake facilities employ systems that eliminate entrainment of fish and other organisms� Passive fine mesh and narrow slot screens have proven effective at reducing entrainment, but examples of such screening systems to perform in the marine environment effec- tively are limited to fouling and maintenance issues� However, the survival and ecological success of the screened organisms are generally without question� Best practice is to locate the passive screen intake in locations with strong ambient currents (sweeping flows) to maximize fine mesh screen performance� The effectiveness of fine mesh and narrow slot screen to reduce entrainment and eliminate impingement is a function of the ratio of intake through screen velocity-to-ambient current velocity�
A number of seawater intake facilities have significantly reduced the biofouling of both intake screens and system conduits through the use of antifouling coatings� Though the antifouling coatings materials and application methods are still experimental, they have proven effective in their earlier stages of service�
Seawater intake wells and other subsurface, infiltration-type structures can have a much greater impact on the existing habitat if they require the excavation of large coastal areas in close proximity to the ocean� After construction, the well pumps, piping, electrical equipment, and their protective enclosures, all necessary for the operation of the system, will occupy a portion of the beach zone�
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