Ultrasonic device for real-time sewage velocity and suspended particles concentration measurements

摘要

In the frame of a technological research and innovation network in water and environmentntechnologies (RITEAU, Re ´ seau de Recherche et d’Innovation Technologique Eau et Environnement),nour research group, in collaboration with industrial partners and other research institutions, hasnbeen in charge of the development of a suitable flowmeter: an ultrasonic device measuringnsimultaneously the water flow and the concentration of size classes of suspended particles.nWorking on the pulsed ultrasound principle, our multi-frequency device (1 to 14MHz) allowsnflow velocity and water height measurement and estimation of suspended solids concentration.nVelocity measurements rely on the coherent Doppler principle. A self developed frequencynestimator, so called Spectral Identification method, was used and compared to the classical Pulse-nPair method. Several measurements campaigns on one wastewater collector of the French city ofnStrasbourg gave very satisfactory results and showed smaller standard deviation values for thenDoppler frequency extracted by the Spectral Identification method.nA specific algorithm was also developed for the water height measurements. It relies on thenwater surface acoustic impedance rupture and its peak localisation and behaviour in the collectednbackscattering data. This algorithm was positively tested on long time measurements on thensame wastewater collector.nA large part of the article is devoted to the measurements of the suspended solidsnconcentrations. Our data analysis consists in the adaptation of the well described acousticnbehaviour of sand to the behaviour of wastewater particles. Both acoustic attenuation andnacoustic backscattering data over multiple frequencies are analyzed for the extrapolation of sizenclasses and respective concentrations. Under dry weather conditions, the massic backscatteringncoefficient and the overall size distribution showed similar evolution whatever the measurementnsite was and were suggesting a global wastewater particles behaviour. By comparison tonsampling data, our data analysis lead to the characterization of two particle groups: the onesnoccurring during rain events and the ones typical of wastewater under dry weather conditions.nEven with already encouraging results on the several weeks of data recorded on severalnwastewater collectors, the validation of our data inversion method is still under progress.n|