1. onstruction: The M-block filter bottom is constructed using plain compact hollow concrete blocks with an approximately M-shaped design.
2. Material: It is prefabricated from high-grade concrete, ensuring durability and strength.
3. Surface: The surface of the M-block is smooth, contributing to efficient water flow.
4. Installation: The blocks are laid in rows on the level filter compartment floor. Importantly, they are neither anchored nor sealed, allowing for straightforward installation.
5. Structural Conditions: The design results in convenient structural conditions, providing stability and support for the filter bed.

Underdrain Mechanism (Filtration):

1. Calibrated Bores: Inside every second row of M-blocks, there is a corrosion-proof pipe containing calibrated bores. This pipe is designed to distribute the inlet flow of scour air evenly over the area of the filter bed.
2. Honeycombed Interior: The interior of the M-block heads is honeycombed, creating a structure that opens into outlet ports at the highest points. This allows air to pass entirely without restriction.
3. Uniform Scour Air Distribution: The honeycombed structure ensures that the scour air entering the distribution system is discharged from the filter bottom in a uniform pattern. The air flow path is positively controlled by the filter bottom.
4. Arched Openings: Large arched openings on the underside of the M-blocks prevent loss of head in the inlet flow of wash water and outlet flow of filtered water.

Backwash Mechanism:

1. Cleaning Process: After a certain time in operation, filters accumulate impurities that must be cleaned through backwashing.
2. Air-and-Water Wash: Backwashing is performed by air-and-water wash. Flows of air and water are introduced through the underdrain system at the bottom of the filter.
3. Even Distribution: The flows are distributed evenly across the entire filter area, and they move concurrently upwards through the filter bed.
4. Impurity Dislodging: As the air and water pass through the filter bed, they dislodge the accumulated impurities, carrying them out of the filter.
5. Wash Water Drainage: The wash water, containing the removed impurities, drains off into a sludge gutter.
6. Air Release: The air used in the backwashing process is released into the atmosphere.

Underdrain System’s Purpose:

1. Support: In normal operation, the underdrain system supports the filter bed and the water head imposed on it.
2. Filtrate Outflow: It permits outflow of filtrate without entraining particles of the filter medium.