Question

A rapid sand filter for a town with water requirement of 1 MLD is to be provided with rate of filtration at $4000l/hr/m^2$, with backwash system. What would be the size of filter and its underdrainage system to the nearest approximation?

• A. 12 and 0.045 sq/m
• B. 11 and 0.020 sq.m
• C. 15 and 0.062 sq.m
• D. 10 and 0.032 sq.m

Answer 1

The correct option is B 11 and 0.020 sq.m

$Sizeoffilter=\frac{Q}{Rateoffiltration}$

$=\frac{1MLD}{4000l/hr/m^2}=\frac{{10}^6}{4000\times 24}{m}^2$

$=10.42m^2$

$\text{Use}11m^2\text{filter}$

$\text{Size of under drainage system}$

$=0.2\%\text{of filter area}=0.020m^2$