Abstract
Urban drainage modelling is a state-of-the-art tool to understand urban water cycles. Nevertheless, there are gaps in knowledge of urban water modelling. In particular pressure drainage systems are hardly considered in the scientific investigation of urban drainage systems, although they represent an important link in its network structure. This work is the conclusion of a series of investigations that have dealt intensively with pressure drainage systems. In particular, this involves the transport of sediments in pressure pipes. In a real-world case study, sediment transport inside a pressure pipe in an urban region in northern Germany was monitored by online total suspended solids measurements. This in situ data is used in this study for the development and calibration of a sediment transport model. The model is applied to investigate sediments transport under low flow velocities (due to energy saving intentions). The resulting simulation over 30 days pumping operation shows that a transport of sediments even at very low flow velocities of 0.27 m/s and under various inflow conditions (dry weather and storm water inflow) is feasible. Hence, with the help of the presented sediment transport model, energy-efficient pump controls can be developed without increasing the risk of deposition formation.
Highlights
IntroductionNumerical simulations are state of the art in challenging problems in urban water management
Numerical simulations are state of the art in challenging problems in urban water management.Whether in wastewater treatment, trying to optimize single or multiple treatment processes, or in sewer systems, for hydraulic optimization or planning and design
The presented 1 D sediment transport simulation in this publication is computed by an uncoupled mathematical model that is based on the advection-dispersion equation (ADE)
Summary
Numerical simulations are state of the art in challenging problems in urban water management. The reduction has several benefits (next to energy saving): It increases the pump duration, reduces the off/on switching frequency, and homogenizes the flow to the downstream sewer system. It might increase the risks of sedimentation and subsequently blockages, as solids are settling when velocity and resulting bed shear stress is below a critical level. Another disadvantage may occur due to the increased retention time inside the pressure pipe. But still simple, numerical model for solids transport inside sewage pressure pipes; Calibrate the model based on ex and in situ determined sedimentation and erosion characteristics; Determine the accuracy of the transport simulation; Investigate and evaluate solids transport under various flow regimes
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