Mousetrap: modelling of real sewer sediment characteristics and attached pollutants

Abstract

A dynamic, pollutograph based sewer flow quality simulation model is an essential tool to aid in the control of intermittent pollution from combined sewer overflows (CSOs). Such a model can be used in conjunction with river impact models to provide an objective methodology for the control of intermittent sewage discharges. A new component to the MOUSE package has been developed, called MOUSETRAP, which is composed of a series of deterministic modules to represent the quality of surface run-off, sediment and pollutant transport within the pipe network, and the biological and chemical reactions within the sewer system. MOUSETRAP can be used to predict sewer flow quality and, hence, CSO spill concentrations and loads over time. The results of recent research into the behaviour of sediments and associated pollutants in sewers have shown that these aspects are crucial to the development of a reliable, deterministic sewer flow quality model. MOUSETRAP, by representing the physical and chemical characteristics and behaviour of real sewer sediment types has the ability to simulate storm event pollutographs incorporating first foul flush phenomena. MOUSETRAP achieves this by representing pollutants associated with dissolved phase liquid transport and pollutants associated with sediments including bed deposits, bed load and settleable suspended solids. The results of data collection are used to characterise sewer sediments and a theoretical basis for the modelling of sediments and sediment attached pollutants in MOUSETRAP is considered. Finally, the model default values for characteristics of the surface, deposited foul flow and in-pipe sediment types in MOUSETRAP are presented.