Explanation: The rate of filtration is highest in pressure filter and its filtration rate lies between 6000 to 15000 litres per hour per m2 of filter area while in rapid sand and roughing filter, it is between 6000 to 8000 litres per hour per m2 of filter area.

Explanation: The loss of head in slow sand filter lies between 15-100cm and of rapid sand filter lies between 30-300cm.The final loss of head in slow sand filter is 100cm while in rapid sand filter is 300cm.

Explanation: As before filtration, sedimentation and coagulation process is done, so the turbidity of water should be less than 35-40ppm.

Explanation: The period of cleaning of a slow sand filter is 1-2 months and that of the rapid sand filter is 2-3 days.

Explanation: The bacterial removal efficiency of the rapid sand filter is90-99%, whereas of a slow sand filter is 98-99%.

Explanation: The grain size distribution of sand in rapid sand filter is stratified with lightest grains at the top and heaviest grains at the bottom.

Explanation: The penetration of suspended matter is deep in rapid sand filter, whereas the penetration of suspended matter is superficial in slow sand filter.

Explanation: Skilled supervision is not required in the slow sand filter but it is essential in the case of the rapid sand filter.

Explanation: The filter run in rapid sand filter should not be less than 24 hours and its head loss should not exceed 2m.

Explanation: The method of cleaning of a slow sand filter involves scrapping of top layer to 15 to 25mm whereas in rapid sand filter involves agitation and back-washing.

Explanation: Rapid sand filters are very efficient in the removal of color and the intensity of color can be brought down below 3 on cobalt scale.