Raf Bouteligier

In Sewer Sediment and Pollutant Transport Models

Several commercial software providers offer in addition to their hydrodynamic urban drainage modeling software a tool for water quality modeling. Yet these quality modeling tools are not common practice in urban drainage design. Prior to start using these quality modules it is of paramount importance to have an insight into these models in order to know what these models (can) do (and cannot do) and how they could be applied. The paper shows the results of a thorough analysis of the quality components of two widely spread hydrodynamic models, namely Mouse (DHI Software, Denmark) and HydroWorks / InfoWorks CS (Wallingford Software, United Kingdom). The focus will be on how both models deal in a different way with the same problem, namely in sewer transport of sediments. The analysis reveals that the adequacy of the quality modules is not as high as compared with the hydraulic model. Care should be taken when using these models. Especially in the case of insufficient field data, the generated results must be analyzed with care and attention. A case study illustrates how the InfoWorks CS software can be used to model the transport of ammonia nitrogen.

Design of self-cleansing sanitary sewer systems with the use of flushing devices.

Many European countries tend to shift from constructing combined sewer systems to separate ones, in order to optimise wastewater treatment efficiency and reduce CSO impact on surface waters. An economic design minimises maintenance requirements by aiming at self-cleansing pipes. However, providing the necessary slopes for self-cleansing sanitary sewer pipes often is unfeasible in flat regions, resulting in an increased risk of loss of hydraulic capacity or blocking. To reduce these risks, flushing tanks can be installed in the sewer system. Where most other researchers contribute to a better understanding of the hydraulics of flushing, this paper rather tries to formulate a methodology to design and test flushing devices in sanitary sewer systems using standards and hydrodynamic simulations. Therefore, several aspects that require consideration when incorporating flushing devices into a sanitary sewer system are discussed. For instance, when flushing sanitary sewers the increase in discharge has to be explicitly considered. A Belgian case study is used to investigate the suitability of the developed methodology. Although the pipe slopes in the methodology are derived assuming uniform flow, the simulation results comply with it. Furthermore, pressurisation of the conduits due to multiple flushing waves remains within acceptable limits.

Implementation of flushing tanks in combined sewer networks to comply with optimal self-cleansing properties

Combined sewer networks are designed to collect and transport the aqueous and solid wastes originating from domestic, industrial and catchment surfaces for tre…