Diameter and Surcharge Effects on Solute Transport across Surcharged Manholes

Abstract

New data are presented describing the retention time and longitudinal dispersion of a solute tracer across circular surcharged manhole structures of different diameters. The variations with both discharge and surcharge level are described and the relationships quantified. The variation of the longitudinal dispersion coefficient exhibits poorly defined trends, however using an aggregated dead zone technique both the reach time delay and travel time show clear variations. A surcharge threshold level for these parameters is evident at the larger manhole diameters and this is explained in relation to jet theory. The variation of the surcharge mean time delay and postthreshold mean travel time are quantified, while the prethreshold travel times are shown to be dependent on both discharge and surcharge. The relationships allow for inclusion in sewer water quality modeling and provide a method for improving predictive techniques.