Real time control of urban wastewater systems—where do we stand today?

doi:10.1016/j.jhydrol.2004.08.010

Journal of Hydrology

Volume 299, Issues 3–4, 1 December 2004, Pages 335-348

https://doi.org/10.1016/j.jhydrol.2004.08.010 Get rights and content

Abstract

This paper presents a review of the current state of the art of real time control (RTC) of urban wastewater systems. Control options not only of the sewer system, but also of the wastewater treatment plant and of receiving water bodies are considered. One section of the paper provides concise definitions of terms frequently used in the literature. Recent developments in the field of RTC include the consideration of the urban wastewater system in its entirety. This allows information from all parts of the wastewater system to be used for control decisions and can lead to a significant improvement of the performance of the wastewater system. Some fundamental concepts of this approach are outlined. Particular emphasis in this paper is laid on methodologies of how to derive a control procedure for a given system. As an example of an RTC system operational in practice, the Québec Urban Community global predictive RTC system is presented. The paper concludes with an outlook into current and future developments in the area of real time control.

The authors are members of the Working Group on Real Time Control of the Joint Committee of the International Association of Hydraulic Research (IAHR) and the International Water Association (IWA).

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.
•

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Real time control of urban wastewater systems—where do we stand today?

Abstract

Introduction

Section snippets

Definitions and key terms

Control objectives

Development and analysis of control procedures

An implementation of RTC: The Québec Urban Community RTC system

Lessons learned: important practicalities

Current trends, future developments

Conclusions

Predictive control of nitrogen removal in WWTPs using parsimonious models

Water quality modeling: a review of the analysis of uncertainty

Water Sci. Res.

Integrating simulation models with a view to optimal control of urban wastewater systems

Modern technologies for real time control of wastewater systems

P units calibration for the RTC of sewer collectors using a dimensionless approach

RTC Applications to the Trondheim–Høvringen wastewater tunnel

Regulator's setup with application to the Roma–Cecchignola combined sewer system

Urban Water

Improving combined sewer overflow and treatment plant performances by real time control operation

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.