Proceedings

The need of accurate flow rate measurements of wastewater is increasing during the last years
in Europe. In UK the M-Cert has come up to fulfill the demand of accurate readings in place,
independent form lab investigations. In place you may find confluences [3]), disturbances [1],
particular downstream conditions. The standard requirements [2] of entrance length to install
flow rate devices are often difficult to obtain. Not all ultrasonic technologies offered for
measurements are able to perform the accuracy demands; only the cross correlation technique
offers the required spatial resolution for the velocity readings to result in velocity profile that
can be converted into a flow rate. These profiles are compared with hydraulic assumptions
based on the log law [4]. Combining this hydraulic with measured velocity values a complete
realistic velocity profile can be calculated resulting in a complete grid. In the past and till now a
grid measurement is the most accepted and reliable technique to determine the volume flow
rate with high accuracy. The use of more sensors gives higher confidence in the grid and may
also take into account asymmetric flow profiles.