Wastewater reuse:: a new approach to screen for designs with minimal total costs

Current process integration tools dealing with the generation of optimal wastewater reuse designs require a lot of effort for data acquisition and frequently suggest designs which are rejected by the process owners due to the ignored constraints or expensive piping needs. In this paper we present a mixed integer linear programming (MILP) model that overcomes both criticisms. Only easily accessible data such as process location, current water demand, and binary information on the reuse possibilities of wastewater streams are required. The total costs, comprising operating costs (freshwater, wastewater treatment, pumping) and investment costs (piping, holding tanks), are minimised for a given time horizon. One characteristic of calculating the piping cost is that splitting and merging of pipes are taken into account. The model was applied to an industrial case study for which several reuse designs were generated and discussed with regard to economical (payback time, investment costs), ecological (total flow rate), and technical aspects. (C) 2001 Elsevier Science Ltd. All rights reserved.