Filter cleaning operations are typically performed using________________?
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Answer: A. scraping and removal in filters slow sand
Explanation
Slow sand filters are cleaned by manually scraping off a thin top layer of dirty sand. This scraping process removes the accumulated organic debris and biological matter clogging the filter bed. It contrasts sharply with rapid sand filters which use reverse water flow to dislodge trapped particles. The top sand layer in a slow sand filter accumulates silt, algae, and bacteria during filtration cycles. After multiple scrapings, clean replacement sand must be added back to maintain the proper bed depth. Manual cleaning requires temporarily taking the filter bed out of service while scraping is performed.
Water treatment plant operators schedule filter maintenance carefully to maintain continuous potable water supply. Understanding filter maintenance requirements helps engineers choose appropriate purification technologies. Labor-intensive scraping makes slow sand filters more suitable for smaller communities with lower labor costs. Backwashing in slow sand filters is incorrect because backflow disrupts the vital biological filter skin. Scraping and removal in rapid sand filters is wrong because rapid filters are cleaned using backwashing. Backwashing in rapid sand filters describes rapid filter maintenance rather than slow sand filter cleaning.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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