filter bed

noun

1. a pond or tank having a false bottom covered with sand and serving to filter river or pond waters.

filter bed

noun

1. See bacteria bed
   a layer of sand or gravel in a tank or reservoir through which a liquid is passed so as to purify it Compare bacteria bed
2. any layer of material through which a liquid is passed so as to filter it

Word History and Origins

Origin of filter bed¹

First recorded in 1870–75

Example Sentences

This valve is opened, and the watery portion is allowed to escape into a sand filter bed.

From Project Gutenberg

So that the last step of our artificial filtration is simply an imitation of nature's great filter-bed.

From Project Gutenberg