An effective technique for wastewater minimisation in batch processes

This paper presents a mathematical formulation for freshwater and wastewater minimisation in multipurpose batch plants. The minimisation of wastewater is achieved through the exploitation of recycle and reuse opportunities. A superstructure that entails all possible recycle and reuse possibilities is used as the basis for the formulation. The existence of an optimal production schedule, which provides starting and finishing times for water using operations, is assumed. The paper addresses the specific case where the contaminant concentration in the outlet water stream from each operation is maintained at its maximum. This condition allows the overall model to be cast as a mixed integer linear programming (MILP) problem for which global optimality is guaranteed. The effectiveness of the developed formulation is demonstrated through a published literature example and a practical case study.