On the accuracy of three dimensional flow measurements at low velocity ranges in municipal wastewater treatment reactors

Abstract

The paper shows investigations about the accuracy of three dimensional flow measurements at low velocity ranges in wastewater treatment reactors. The investigations were carried out at a conventional rectangular primary clarifier, and a pre-anoxic tank. Both structures are very frequently used at large municipal wastewater treatment plants, but operated for different aims (sedimentation, denitrification, respectively). Therefore the analysis of the measurement and data recorded by Acoustic Doppler Velocimetry (ADV) is useful for operators, co-workers and researchers, who would like to investigate existing, unified treatment units with various flow patterns. Moreover, the paper provides general constructive recommendations for the preparation of such in situ measurement campaigns, data evaluation and the determination of uncertainties often considerably deteriorating the interpretation of the results.