Describe the construction and function of rapid sand filter.

A rapid sand filter is constructed as a multi-stage system for the treatment of wastewater. It is costlier and a little bit complex to design so not small communities or every developing nation can adopt it.

coarse sand and granular particles act as media to remove impurities in form of flocs gained from the flocculation process with help of a chemical basically alum. So mostly silica sand is used and it is called rapid filtration instead of rapid sand filtration in a modernized way. And then it is passed through filter media and flocs are traped under gravity flow.

And two types of rapid sand filters are gravity and pressure.

This filter system has less effect on the taste, smell, and dissolved impurities of drinking water, but activated carbon media is also included in the system. This filter system needs to clean from time to time, it should be done by the backwashing method which functions by reversing water direction with compression air. But we need to take care of media not flowing out with backwashing water.