FILTER UNDER DRAINAGE

Application

The “Filter Under Drainage” is one of the key components of water treatment plants, especially in rapid sand filtration systems. The bottom drain at the filter floor is meant to collect evenly the filtered water after it passes through the filter media (such as sand, gravel) and convey it to the clear well or subsequent treatment stages. It also ensures even distribution of backwash water over filter bed when the cleaning is done, so that trapped particles are removed one by one and cleaning is effective otherwise the media gets clogged up.

Operation

The operation of a filter under drainage system involves two primary functions:

Filtration Mode: In filtration mode, water moves downward through the filter media, and the under-drain system collects the treated water evenly to reduce pressure drop and to prevent channeling or dead space in the filter bed.
Backwash Mode: During backwashing, water or air is pumped up through the under-drain system in the reverse direction, loosening filter media and dislodging solids that have built up. Filtered water then passes through the under-drain system, in which a uniformly distributed flow cleans the filter bed and reinstates its filtration capacity.

Screening

Conveying

Process Equipment

Water Control Gates

Sludge Dewatering

Filtration