Integrated Water Networks Research Articles

Global Optimization for the Synthesis of Integrated Water Systems with Particle Swarm Optimization Algorithm

The problem of optimal synthesis of an integrated water system is addressed in this study, where water using processes and water treatment operations are combined into a single network such that the total cost of fresh water and wastewater treatment is globally minimized. A superstructure that incorporates all feasible design alternatives for wastewater treatment, reuse and recycle, is synthesized with a non-linear programming model. An evolutionary approach—an improved particle swarm optimization is proposed for optimizing such systems. Two simple examples are presented to illustrate the global optimization of integrated water networks using the proposed algorithm.

Global optimization of multiscenario mixed integer nonlinear programming models arising in the synthesis of integrated water networks under uncertainty

The problem of optimal synthesis of an integrated water system is addressed in this work, where water using processes and water treatment operations are combined into a single network such that the total cost of building the network and operating it optimally is globally minimized. The network has to be designed to be feasible and optimal over a given set of scenarios in which different operational conditions hold. The uncertain operational parameters in the system are the amount of contaminants generated in the process units and the extent of removal of the contaminants inside the treatment units. We optimize a superstructure that incorporates all feasible design alternatives for wastewater treatment, reuse and recycle, with a multiscenario nonconvex mixed integer nonlinear programming (MINLP) model, which is a deterministic equivalent of a two-stage stochastic programming model with recourse. These models can grow in size with the number of scenarios and often require exponential computational effort to be solved to rigorous global optimality. To effectively solve this problem, we propose a spatial branch and cut algorithm that uses Lagrangean decomposition for global optimization of the large multiscenario model. Two examples are presented to illustrate the global optimization of integrated water networks operating under uncertainty using the proposed algorithm.

Integrated Water Network Designs for Batch Processes

A general mixed-integer nonlinear programming (MINLP) model is developed in this study to synthesize water networks in batch processes. The proposed model formulation is believed to be superior to the available ones. In the past, the tasks of optimizing batch schedules, water-reuse subsystems, and wastewater treatment subsystems were performed individually. In this study, all three optimization problems are incorporated in the same mathematical programming model. By properly addressing the issue of interaction between subsystems, better overall designs can be generated. The resulting design specifications include the following: the production schedule, the number and sizes of buffer tanks, the physical configuration of the pipeline network, and the operating policies of water flows. The network structure can also be strategically manipulated by imposing suitable logic constraints. A series of illustrative examples are presented to demonstrate the effectiveness of the proposed approach.

Using optimisation for integrated water network management

Abstract The water industry has undergone radical change in the late 1980s and changes continue apace. We have been, and will continue to be, under increasing pressure to reduce costs and increase service within a framework where regulations are becoming tighter and demanding more information to achieve and substantiate performance. The major challenge will lie with the leaders of the industry. They have to achieve the right attitude, management technique and technical excellence to meet the requirements of change and to create adaptable organizations that can manage the challenges of change in a positive and proactive way. Cultural change has started but has a long way to go. We must overcome the traditional attitude of many water suppliers, which has typically been one of the ‘professional stewardship’ of a resource in which they supply water in the way they believe to be best. This must change and is changing to a more commercially minded management which is ‘customer centred’ rather than ‘product centred’. We must realize that our organizations manage a complex asset base which has to work towards strictly defined objectives of service quality, operational efficiency and regulatory requirements, all of which, as time goes on, are influenced more and more by substantial external forces.