- UPSC Civil Service Exam Questions - Section 1
- UPSC Civil Service Exam Questions - Section 2
- UPSC Civil Service Exam Questions - Section 3
- UPSC Civil Service Exam Questions - Section 4
- UPSC Civil Service Exam Questions - Section 5
- UPSC Civil Service Exam Questions - Section 6
- UPSC Civil Service Exam Questions - Section 7
- UPSC Civil Service Exam Questions - Section 8
- UPSC Civil Service Exam Questions - Section 9
- UPSC Civil Service Exam Questions - Section 10
- UPSC Civil Service Exam Questions - Section 11
- UPSC Civil Service Exam Questions - Section 12
- UPSC Civil Service Exam Questions - Section 13
- UPSC Civil Service Exam Questions - Section 14
- UPSC Civil Service Exam Questions - Section 15
- UPSC Civil Service Exam Questions - Section 16
- UPSC Civil Service Exam Questions - Section 17
- UPSC Civil Service Exam Questions - Section 18
- UPSC Civil Service Exam Questions - Section 19
- UPSC Civil Service Exam Questions - Section 20
- UPSC Civil Service Exam Questions - Section 21
- UPSC Civil Service Exam Questions - Section 22
- UPSC Civil Service Exam Questions - Section 23
- UPSC Civil Service Exam Questions - Section 24
- UPSC Civil Service Exam Questions - Section 25
- UPSC Civil Service Exam Questions - Section 26
- UPSC Civil Service Exam Questions - Section 27


UPSC Civil Service Exam Questions - Engineering
Q1: The cleaning of slow sand filter is done byA
reversing the direction of flow of water
B
passing air through the filter
C
passing a solution of alum and lime through the filter
D
scraping off the top layers of sand and admitting water
ANS:D - scraping off the top layers of sand and admitting water A small biological sand filter (slow sand filter or Biosand filter) is maintained or cleaned by actively managing only the top 5 cm of sand. This top layer is either removed and replaced when the flow rate becomes unacceptable (typically 4 to 6 months) with clean sand or "wet harrowed" meaning the sand is gently agitated causing partial break up of the biological surface. This may be slightly different for a very large slow sand filter; more sand and more work. A rapid sand filter is maintained and cleaned by forcefully injecting water backwards through the entire sand bed every 2 or 3 days. Backwashing a biological sand filter will destroy it and may result in people getting very sick if water from it is being consumed. |


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