| 11. | Maintenance means backwashing where the flow of clean water is reversed back into the filter.
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| 12. | :: : Recent studies have assessed to combine relaxation and backwashing for optimum results,.
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| 13. | Slow sand filters and self-cleaning screen filters employ mechanisms other than backwashing to remove trapped particles.
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| 14. | Relaxation and backwashing effectiveness will decrease with operation time as more irreversible fouling accumulates on the membrane surface.
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| 15. | A typical backwashing session can waste a few hundred gallons of water water that must be replaced.
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| 16. | Alternatively, in engineering applications, such as swimming pool water treatment plants, they may be cleaned by backwashing.
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| 17. | Self-cleaning screen filters utilize point-of-suction backwashing to clean the screen without interrupting system flow.
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| 18. | Finally, iron filter media requires high flow rates for proper backwashing and such water flows are not always available.
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| 19. | Small amounts of sand can be lost in the backwashing process and the bed may need to be topped up periodically.
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| 20. | Backwashing is an important operation employed to remove filtered solids as this build up causes resistance to filtration to increase with time.
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