Real time control of urban wastewater systems—where do we stand today?
Introduction
Urban wastewater systems, having sewer system, wastewater treatment plant and receiving water as their main elements, can be found throughout the world. Many of them are operated with little or no control. On the other hand, there are some case studies with quite sophisticated forms of control. What are the benefits of such control? What are the drawbacks? The last state-of-the-art report on real time control of urban drainage systems has been published more then a decade ago (Schilling, 1989). What has happened since then? What are the recent developments in this area since then? Why should we embark on real time control? Also, many readers—now half a generation later—may be new to this topic. Therefore, this survey paper attempts to give an introduction to the current state of the art of real time control of urban wastewater systems.
The question raised ‘why should we bother with real time control today?’ has, at least, three valid answers: There is progress in measurement technology, the consideration of water-quality-based objectives and the integrated approach to control open up new potential, and, finally, methodologies and tools assisting in the development of control procedures have improved. Also a number of large-scale case studies demonstrate that real time control does indeed work in practice. This paper attempts to illustrate some of these concepts, with some emphasis being put on real time control (RTC) of sewer systems.
Section snippets
Definitions and key terms
This section introduces some of the fundamental concepts and terms of RTC. Subsequent sections then discuss how control procedures are actually determined for a given case study, followed by an example of an implementation of real time control in Québec. Further sections outline some important practical issues as well as current and future trends of RTC.
An urban wastewater system is controlled in real time if process variables are monitored in the system and, (almost) at the same time, used to
Control objectives
Traditionally, sewer system, treatment plant and receiving water have been considered as separate units. Also control, where it was performed, was—and often still is—done for each of these parts separately (see, for example, the reports by Schilling, 1989; Olsson and Newell, 1999; Jeppsson et al., 2002; Jumar and Tschepetzki, 2002).
When formulating objectives of control or, more generally spoken, defining performance indicators for sewer systems, one traditionally uses auxiliary criteria such
Development and analysis of control procedures
A real time control system usually is structured in different hierarchical levels, i.e. field (process), system and management levels (Fig. 2). The management level involves the specification of the overall way of operation. On the system level, the magnitude and the time sequence of the various set-points in the real time control system are specified. On the field level, controllers adjust actuators to achieve minimum deviations of the regulated variables from their set-points.
A core task in
An implementation of RTC: The Québec Urban Community RTC system
This section, describing as an example the RTC system of Québec Urban Community (QUC), illustrates that RTC does not merely consist of some theoretical ideas, but that it has indeed found its way into practical application. QUC has implemented a global optimal predictive real time control system and has operated it since summer 1999. It involves solution of a multi-objective optimisation problem. It consists of finding the flow set-points that minimise the value of a multi-objective (cost)
Lessons learned: important practicalities
Some of the lessons learned from the Québec real time control system and from other applications can be summarized as follows:
Costs. Costs of planning studies for RTC can be quite high: usually, a computer model for the system has to be set up, calibrated and verified. However, implementation of RTC, which makes use of existing wastewater infrastructure and also can provide significant and quick environmental benefits, can help to prevent building new tanks or extending the capacity of existing
Current trends, future developments
In this section, some ideas and trends that the authors expect to develop in the coming decade are presented. Starting from the visible shift in operational objectives driven by re-oriented legislation, future characteristics of practical tools for RTC design and implementation are presented. These include, in particular, modelling approaches, measurement systems, actuators and, of course, new control strategies and procedures which are more closely linked to the new objectives.
Objectives. Many
Conclusions
As key lessons on the current state of the art in real time control of urban wastewater systems can be stated
- •
Today, improved devices, methodologies and tools for are available which allow real time control of urban wastewater systems to be considered as an option to minimise adverse impacts on the environment and to minimise costs.
- •
Due to improved methods, even those wastewater systems may have potential for real time control which, in the past, did not appear to be able to benefit from RTC.
- •
References (51)
- et al.
Predictive control of nitrogen removal in WWTPs using parsimonious models
(2002) - Bechmann, H., 1999. Modelling of Wastewater Systems. PhD Thesis. Technical University of Denmark,...
Water quality modeling: a review of the analysis of uncertainty
Water Sci. Res.
(1987)- et al.
Integrating simulation models with a view to optimal control of urban wastewater systems
(2001) - et al.
Modern technologies for real time control of wastewater systems
(2002) - et al.
P units calibration for the RTC of sewer collectors using a dimensionless approach
(2002) - et al.
RTC Applications to the Trondheim–Høvringen wastewater tunnel
(2000) - et al.
Regulator's setup with application to the Roma–Cecchignola combined sewer system
Urban Water
(2000) - et al.
Improving combined sewer overflow and treatment plant performances by real time control operation
(2003) - CEC—Council of the European Communities, 2000. Directive of establishing a framework for community action in the field...
Dynamical modelling and estimation in wastewater treatment processes
Ranking stormwater control strategies under uncertainty: the River Cam case study
Water Sci. Technol.
Real-time control for two communities—technical and administrational aspects
Integrated modelling for analysing and optimisation of wastewater systems—the Odenthal case
Urban Water
Model based real-time control of sewer system using fuzzy-logic
Water Sci. Technol.
Status and future trends of ICA in wastewater treatment—a European perspective
Water Sci. Technol.
Implementation of a wastewater treatment operation support tool based on on-line simulation
Water Sci. Technol.
Des îlots de survie pour les poissons
Is combined sewer overflow spill frequency/volume a good indicator of receiving water quality impact?
Urban Water
Operation and performance of an optimized real time control system for wet weather pollution control
Model reduction through boundary relocation to facilitate real-time control optimisation in the integrated urban wastewater system
Water Sci. Technol.
Fast, simultaneous simulation of the integrated urban wastewater system using mechanistic surrogate models
Water Sci. Technol.
Real time control of the integrated urban wastewater system using simultaneously simulating surrogate models
Water Sci. Technol.
Cited by (231)
Model predictive control and rainfall Uncertainties: Performance and risk analysis for drainage systems
2024, Journal of HydrologyA framework for real-time operation of urban detention reservoirs: Application of the cellular automata and rainfall nowcasting
2024, Journal of Environmental ManagementReal-time model predictive control of urban drainage system in coastal areas
2024, Journal of HydrologyEvaluating real-time control of stormwater drainage network and green stormwater infrastructure for enhancing flooding resilience under future rainfall projections
2023, Resources, Conservation and RecyclingFlooding mitigation through safe & trustworthy reinforcement learning
2023, Journal of Hydrologypystorms: A simulation sandbox for the development and evaluation of stormwater control algorithms
2023, Environmental Modelling and Software