• skimmer

• straining bag

• loose filter

• to sift

• grating

• filter cartridge

• bolting-cloth

• filter paper

• precoat

• bolting-cloth

• defecation mud

• to act as a filter, to function as a filter

• air filter

• filter

• infiltration, leak

• filter-tip, filter-tipped

• selective filters

• clarifier

• to filter through, to leach, to ooze, to percolate, to seep, to sift, to strain

• percolation, permeation

• by-pass