Test: Rapid Sand Filter

Explanation: The depth of an enclosed tank of a rapid sand filter lies in the range of 2.5-3.5m and its surface area lies between 20-50m².

Explanation: The effective size of a rapid sand filter lies in the range of 0.35-0.6mm and its common value is 0.45mm.

Explanation: The finer the suspended impurities to be removed, smaller will be the sand size in order to increase the surface area of sand grains in the sand bed.

Explanation: The value of uniformity coefficient in a rapid sand filter lies between 1.2 and 1.7 and its common value is 1.5.

Explanation: The effective size of Anthracite when used as a filter material lies between 0.7-0.75mm and its uniformity coefficient is 1.75.

Explanation: Sand depth should be such that floc do not break through the sand bed and the depth of sand should vary between 60-90 cm.

Explanation: Anthracite is a costlier filter material used in industrial filter which is more inert to hot caustic solutions than sand.

Explanation: The minimum depth of sand of a rapid sand filter is given by
Qd³h/l=B*29323, Where Q=filtration rate, d =sand size, H= head loss, l=depth of sand bed, B=break through index.

Explanation: The base material of a rapid sand filter consists of 45-60 cm thick gravel bed which is laid in layers of 15 cm with finer topmost layer (2-6mm) and coarser bottom layer (20-50mm).

Explanation: In Perforated pipe system, laterals are provided with strainers. Strainers are made of brass or bronze and are in umbrella shape, having a small perforation. They distribute the wash water without jet action.