Design of grit channels controlled by Parshall flumes

• Published in: WATER SCIENCE AND TECHNOLOGY Vol. 33; no. 3; pp. 195 - 210
• Main Authors: v.R. Marais, Gerrit, van Haandel, Adrianus C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: London Elsevier Ltd 01-01-1996; IWA Publishing
• Subjects: Effluents; Flow rates; Flow velocity; Flumes; Gravitation; Gravity; Grit; Grit channel Parshall flume; Grit removal; Low flow; Q1; Removal; Sewage; Sewage disposal; Sewage treatment; Sewage treatment plants; Velocity; Waste water pre treatment; Wastewater treatment; Weirs; Grit removal; Grit channel Parshall flume; Waste water pre treatment
• ISBN: 9780080428956; 0080428959
• ISSN: 0273-1223; 1996-9732
• DOI: 10.1016/0273-1223(96)00313-7

Grit removal is a necessary pre treatment step in sewage treatment. Grit can be separated from the liquid phase by gravity settling in a channel. For an adequate performance of the pre treatment unit, it is necessary that the liquid velocity in the channel is kept approximately constant, even when the flow rate varies. This can be accomplished by coupling a channel with a rectangular cross section to a Parshall flume, provided the channel bottom level is placed at a higher level than the flume base. The height of the step between the two devices depends on the magnitude and variation of the sewage flow. At low flow rates the step will start to act as a weir and can take over the function of the Parshall flume as the liquid velocity controlling device, thereby extending significantly the range of flow rates that can be degritted in the pre treatment unit.