Application of predictive control strategies to the management of complex networks in the urban water cycle [Applications of Control]

Abstract

The management of the urban water cycle (UWC) is a subject of increasing interest because of its social, economic and environmental impact. The most important issues include the sustainable use of limited resources and the reliability of service to consumers with adequate quality and pressure levels, as well as the urban drainage management to prevent flooding and polluting discharges to the environment.Climate change is expected to produce regional changes in water availability in the 21st century. For example, Northern and Southern Europe are expected to experience, respectively, an increase and a decrease in mean precipitation, as well as an increase in the magnitude and frequency of extreme events [1]. These changes will have direct consequences through impacts on the availability and quality of water in the water cycle. Optimal management strategies for the systems in the water cycle can contribute to reduce the vulnerability of urban water systems (UWS) to climatic variability and change.An UWC is mainly comprised of the following systems: (i) Supply/production: water supply from superficial or underground sources and treatment to achieve necessary quality levels, (ii) transport networks, which use natural or artificial open-flow channels and/or pressurized conduits to deliver water from the treatment plants to the consumer areas, (iii) water distribution to consumers, involving pressurized pipeline networks, storage tanks, booster pumps and pressure/flow control valves, (iv) urban drainage and sewer systems carrying waste-and rain water together to wastewater treatment plants (WWTP), before returning it to the receiving environment. In urban environments, drinking water is provided by means of a drinking water network (DWN) to consumers and industry, and sanitation/urban drainage is achieved through a sewer network (SN). In a large number of cities, DWNs are managed using telemetry and telecontrol systems which provide, in real time, pressure, flow, quality and other measurements at several key locations within the network. Flow, pressure and storage control elements are operated from a central dispatch in a centralized or decentralized scheme.In some cases, advanced urban drainage systems also include sewage control infrastructure, such as detention tanks, pumps, gates and weirs. All these elements are monitored and controlled by using telemetry/telecontrol systems, which involve rain-gauge networks, wastewater level and/or flow meters in the sewers and actuators at the valves, pumps and weirs, a communication network, and monitory and control software. The control system manages the flows and the storage in the network in order to minimize the risk of untreated water overflows to the streets or to the receiving environment.The use of optimal control for managing water systems to achieve energy efficiency, cost minimization and environmental protection is summarized in this article. Applying optimal control concepts to water systems requires the development of control-oriented dynamic models to represent...

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