ABSTRACT
This paper presents continuous field experiments carried out during 4 years in a man-entry egg-shaped combined sewer in Lyon, France in order to contribute to the knowledge and the modelling of sediment accumulation and sediment removal by means of a Hydrass flushing gate. The 250 microm sediments are mainly mineral, and their physical and chemical characteristics appear as rather stable in time and space. Long-term sediment monitoring reveals: (i) a regular asymptotic increase of both the sediment mass and the slope of its longitudinal profile, (ii) a clear correlation between local sediment profile irregularities and sewer ancillaries but without significant influence on the global and long term accumulation. Simple sediment accumulation modelling shows: (i) a good suitability of a three parameters conceptual model to reproduce asymptotic sediment volume accumulation, and (ii) a good suitability of the Velikanov model to reproduce sediment profiles. Both models reproduce observations with an acceptable margin of uncertainty for operational management purposes but are very sensitive to input data and parameter values. The Hydrass flushing gate is efficient and it appeared that the mass of sediments moves downstream linearly with the number of flushes.
Subject(s)
Drainage, Sanitary , Sewage , Waste Disposal, Fluid/instrumentation , Facility Design and Construction , Models, Theoretical , Research Design , Waste Disposal, Fluid/methods , Water MovementsABSTRACT
This paper presents field experiments carried out in a 1.8 m height egg-shaped sewer in Lyon, France in order to contribute to the knowledge and the simulation of Hydrass flushing gates. The main results are: i) definition of an empirical relationship giving the flow discharged by the gate as a function of the upstream water level and its use in modelling the gate behaviour, and ii) observation of the flush propagation along the sewer and evaluation of the potential cleansing efficiency.
