The following characteristic pertain to the sand filters used in
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The following characteristic pertain to the sand filters used in the water industry.
I. Filtration rate is 1 to 4 m3/(m2 day)
II. Typical duration of cleaning interval is 24 to 72 hours
III. Operation cost is low
Which of the above characteristic pertain to slow sand filters?A. I, II and III
B. I and II
C. II and III
D. I and III
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
Slow sand filter: They consist of fine sand, supported by gravel. They capture particles near the surface of the bed and are usually cleaned by scraping away the top layer of sand that contains the particles.
Cleaning:
a) For cleaning, the top layer of sand is scrapped, and 1.5 to 3 cm of sand is removed in each cleaning.
b) The frequency of cleaning is 1 to 3 months.
c) Rate of filtration is 1-4 m3/day/m2 of filter area.
It is used for smaller plants in villages because it is economical and has very low operation cost.