Towards an effective scheduling technique for zero-effluent multipurpose batch plants

Abstract

Currently, wastewater minimization methodologies for batch processes are focused on reusing and recycling wastewater between units. Once this water has reached a certain concentration level or there are no feasible reuse or recycle opportunities within a time period the water is then discarded as effluent. Invariably there will always be a minimum amount of wastewater generated. In some processes the wastewater produced contains valuable product, such as wastewater produced in a pharmaceutical operation. The only way to recover the product is to use the wastewater as a product constituent in a batch of similar product. Reuse of wastewater in this manner leads to a process that can produce zero water effluent. The methodology derived makes it possible for the operation of a zero-effluent facility and is based on the uneven discretization of the time horizon using time points. The inherent reuse and recycle opportunities of wastewater, coupled with dedicated storage vessels ensure that the required goal is met. A pharmaceuticals case study is used to demonstrate its effectiveness.