System-wide Benchmark Simulation Model for integrated analysis of urban wastewater systems

Interactions between different components (sewer, wastewater treatment plant (WWTP) and river) of an urban wastewater system (UWS) are widely recognized (Benedetti et al., 2013). This has resulted in an increasing interest in the modelling of the UWS. System-wide models take into account the interactions between the different subsystems and allow us to operate the UWS in a holistic manner.

Such an integrated approach makes it feasible to evaluate control strategies at an UWS scale with the aim of improving receiving water quality. Currently, benchmark simulation models are widely used to evaluate local and plant-wide control strategies in WWTPs (Jeppsson et al., 2013). The International Water Association (IWA) Benchmark Simulation Models (BSM1, BSM1_LT, BSM2) consist of a predefined plant layout, process models, sensor and actuator models, influent characteristics and evaluation criteria (Gernaey et al., 2014).

Given the success of BSMs in evaluation of control strategies for WWTPs, it is envisioned to spatially expand the plant-wide BSM to a system-wide tool. A system-wide BSM can then play an important role, not only in the evaluation of integrated control strategies, but also in developing a better understanding of the interactions between different components of an UWS.

This paper aims at presenting a system-wide benchmark simulation model that includes catchment, sewer network, WWTP and receiving water subsystems. A hypothetical UWS layout is defined and an integrated model for this system is developed. Modelling details for various building blocks of the model are explained in the following sections of this abstract.

Preliminary simulation results are used to evaluate the impact of rain events using indirect (emission measures from sewers and WWTPs) and direct (river quality based) measures. We demonstrate the need of using a holistic approach due to the strong interactions between the elements of the UWS (catchment, WWTP and sewer).