Rigorous Targeting Approach for Water Reuse and Wastewater Minimization in Industrial Processes

Water reuse/recycle is one of the key strategies in reducing the freshwater flow rate in the process industries. The problem involves the allocation of internal water and freshwater sources to process units considered as demands with the objective of minimizing freshwater feed and wastewater discharge. However, several graphical and numerical techniques have been developed to target freshwater flow rate. In this paper, we present a new rigorous numerical targeting approach to minimize the utilization of freshwater and identify wastewater streams ahead of detailed design of the recycle/reuse network. First, the problem is formulated mathematically to establish rigorous rules for targeting and designing water network. Then, targeting algorithm is elaborated to make this methodology more practical. The numerical technique is useful in locating pinch point, which provides insightful information on the utilization of freshwater, identification and discharge of wastewater streams. In fact, examples for both models of fixed flow rate and fixed load problems are solved to illustrate the ease, rigor, and applicability of the developed targeting technique. Hence, this technique is extended to deal with a combined problem of fixed flow and fixed load.