HORUS: a conceptual model of pollution simulation in sewer networks

This paper presents the conceptual model for solid production and transfer in combined or separate sewerage systems called HORUS. The objective of this model is, taking into account the characteristics of the catchment and the structure of the sewerage system, to reproduce the hydrographs, Total Suspended Solids (TSS) and Chemical Oxygen Demand (COD) concentration generated by any rainfall. HORUS consists of main connected modules and the retained algorithms have been chosen after using a special Testing Bench of Pollution Modelling Algorithm in Urban Sewer System. The main modules are: a hydrological module (linear reservoir and runoff losses), a hydraulic module (described by the Muskingum model), a module for solids production and transport (build-up and washoff of catchment and solid transport in sewer) and a module for numerical optimisation. The improvement of the HORUS model is shown by a comparison between simulation results versus the initials algorithms. Simultaneous measurements of rainfall, hydraulic, TSS and COD concentrations on nine very different catchments and about one hundred rainfall events allowed a large range of validation which can be considered of good quality. HORUS provides a satisfying fitting of the real TSS and COD pollutographs (flow and concentration) and this, considering the global form, maximal values and the temporal position.