Targeting and synthesis of single-impurity total water systems using coordinated transhipment models

Reuse, regeneration and recycle are common practices for attaining maximum savings in industrial water networks. Additional benefits are generated when the selection of the regeneration technology takes place prior to the detailed design of the network and at the same time with the calculation of targets for fresh water use and wastewater treatment flows. This paper proposes a new methodology for targeting fresh water requirements and wastewater treatment flowrates, synchronized with the selection of the most cost-effective treatment technologies. The problems under study involve water systems with single impurities and water-using operations with fixed contaminant loads and/or fixed flowrates. The treatment processes are characterized by either fixed outlet concentrations or fixed removal ratios. Total water systems are simulated by two transhipment models; one for the system of water-using operations and a second for the wastewater treatment system. The procedure coordinates the two models into simultaneously targeting clear water use, calculating minimum recycle and treatment flows and selecting wastewater treatment technologies. The procedure offers the advantage of producing optimal solutions ahead of design, while critical system parameters can be detected through the pinch technology built in the transhipment models, offering the possibility to identify possibilities for improvement through process modifications. The new approach is illustrated using five examples with different system characteristics, and the results are validated and represented graphically using a superstructure optimization model of the systems.