Flow measurement in waste water industry

Basic principles
There is a distinction between municipal and industrial waste water. Municipal waste water contains rainwater and domestic waste water. Depending on industry, industrial waste water contains organic solvents and acids.

There are several procedures available for measuring the flow of these waters:

Hydraulic procedure

• Measurement of water levels with and w/o change in the channel cross-section
• With controlled cross-section: Change in flow (falls, weirs); change in channel width (Venturi channel)
• Without controlled cross-section: Flow or medium flow speed are determined by way of the energy lines drop

Definition of medium flow speed
Traversed cross-section multiplied by flow speed Q = FxVm

• Ultrasonic meters time/doppler
• Electromagnetic flow meters (MAG meters)

Waste water drainage
As for drainage and flow measurement in sewer constructions, the flow is not directly measured but in case of the magnetic inductive flow measurement, the flow is determined according to the principle of continuity, i.e. as a product of the measured medium flow speed v and the traversed cross-section A.
Q = A* v .
The traversed section is constant or is kept constant by culvert MAGs in cases where pipes are not completely filled and while doing so, a completely filled measurement cross-section is available.
Final bends showing to the top or risers can be used as culverts flanged to the MAG meter.