Most of the methodologies published in literature on wastewater minimisation for batch
processes are based on short-term scheduling techniques. When these methods are applied to
longer time horizons, the computational time becomes intractable, hence the focus of this
thesis. This thesis presents a methodology for simultaneous optimization of production
schedule and wastewater minimisation in a multipurpose batch facility. The key feature of the
presented methodology is the adaption of cyclic scheduling concepts to wastewater
minimisation. The methodology is developed based on continuous-time formulation and the
state sequence network (SSN) representation. The methodology is successfully applied to two
common literature examples and an industrial case study to demonstrate its effectiveness.
None of the currently published wastewater minimisation techniques could solve the case
study for a time horizon of 168h. However, through the application of the presented
methodology, a time horizon of 168h for the case study was reduced to 8 cycles with the
cycle length of 23h, for which the CPU time for the optimum cycle is 64.53s.
Dissertation (MEng)--University of Pretoria, 2011.