A graphical technique for wastewater minimisation in batch processes

Presented in this paper is a graphical technique for freshwater and wastewater minimisation in completely batch operations. Water minimisation is achieved through the exploitation of inter- and intra-process water reuse and recycle opportunities. In the context of this paper, a completely batch operation is one in which water reuse or recycle can only be effected either at the start or the end of the process. During the course of the operation, water reuse and recycle opportunities are completely nullified. The intrinsic two-dimensionally constrained nature of batch processes is taken into consideration. In the first instance, time dimension is taken as a primary constraint and concentration a secondary constraint. Subsequently, the priority of constraints is reversed so as to demonstrate the effect of the targeting procedure on the final design. Attention is brought to the fact that first and cyclic-state targeting are essential in completely batch operations. Moreover, the exploration and use of inherent storage in batch processes is demonstrated using a real-life case study. Like most graphical techniques, the presented methodology is limited to single contaminants.