PARSHALL FLUME

It is important to know how much wastewater is entering the plant. Many operational decisions are based on flow. Also, many of the plant’s state-mandated performance parameters are based on flow. The Parshall flume is an open-channel flow measuring device used in many treatment plants. Basically, it is a section of channel with a specially-shaped constriction. The constriction causes the flow to back up into the upstream channel. The greater the flow, the deeper the water ahead of the constriction. The height of the flow in the upstream section is measured by an ultrasonic level meter (the small, white object in the upper center of the photo) and the flow rate is calculated in millions of gallons per day.