Unit: 6 

Design criteria and Design of Rapid Sand Filters with under drainage system 

Rapid sand filters are a type of water treatment filter that are commonly used to remove suspended solids, turbidity and other impurities from water. The design criteria for rapid sand filters include: 

High Flow Rate: Rapid sand filters are designed to handle high flow rates of water to ensure that they can treat the required volume of water in a timely manner.

High Removal Efficiency: Rapid sand filters are designed to remove a high percentage of suspended solids and other impurities from the water.

Low Headloss: To minimize the energy required to pump water through the filter, the headloss should be kept as low as possible.

Durability: Rapid sand filters should be made of materials that are resistant to corrosion and abrasion, and can withstand the harsh conditions of water treatment.

A typical design of a rapid sand filter includes the following components:

A tank or vessel: The tank is usually made of concrete or steel and is designed to hold the sand and gravel media.

Under Drainage System: It is a system of pipes or other components that are placed at the bottom of the filter. It allows for the collection and removal of the filtered water and also helps to distribute the incoming water evenly across the filter bed.

Sand And Gravel Media: The sand and gravel media are placed in the filter tank and are used to remove impurities from the water.

Control valves: These valves are used to control the flow rate of water entering and leaving the filter.

Effluent Trough: The effluent trough is used to collect the filtered water as it exits the filter.

Backwash system: A backwash system is used to periodically remove the accumulated impurities from the filter media.

Control Panel: The control panel is used to control and monitor the operation of the filter, including the flow rate and the backwash cycle.