spiral flow tank

spiral flow tank

[′spī·rəl ′flō ‚taŋk]
(civil engineering)
An aeration tank of the activated sludge process into which air is diffused in a spiral helical movement guided by baffles and proper location of diffusers.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.