Question

The following characteristics pertain to the sand filters used in water industry.

I. Filtration rate is $1to4m^3/m^2/day$.

II. Typical duration of operation in one run is 24 to 72 hours.

III. Operation cost is low.

Which of the above characteristic pertain to slow sand filters?

• A. I and II
• B. I, II and III
• C. II and III
• D. I and III

Answer 1

The correct option is D I and III

The frequency of cleaning of slow sand filters is 1-3 months, hence is the typical duration of operation. Statement II is wrong.

Filtration rate for design is taken as $100-200//hr/m^2$ which is in the range given in statement I

Operation cost is low since it is worked over by gravity and no other energy source is required.