Question

What is the rate of filtration in a slow sand filter used for water purification?

• A. $300to600litres/hour/m^2$
• B. $500to1000litres/hour/m^2$
• C. $3000to6000litres/hour/m^2$
• D. $100to200litres/hour/m^2$

Answer 1

The correct option is D $100to200litres/hour/m^2$

$\text{Specifications of slow sand filter}$

$D_{10}\text{of filter medium = 0.2 - 0.3 mm}$

$\frac{D_{60}}{D_{10}}\text{= Uniformity coefficient = 5}$

$\text{Design period = 10 years}$

$\text{Rate of filtration 100-200}l/hr/m^2$

$\text{Efficiency of slow sand filter in bacterial removal 97-98\%}$

$\text{Filter cannot be used if turbidity > 50 ppm}$