Process integration design methods for water conservation and wastewater reduction in industryPart 2: Design for multiple contaminants

This paper is part 2 of a three-part series of papers addressing operational techniques for applying mass integration design in industry with special focus on water conservation and wastewater reduction. This paper presents a design technique for any number of wastewater streams containing multiple contaminants. The technique comprises a single non-linear optimization program to minimize the wastewater discharged (or maximize the amount of recycled wastewater). This program is developed based on general water allocation principles and uses the transshipment model theory to allow the "shipment" of wastewater (referred to as "sources" or "warehouses") to process water users (referred to as "sinks", "demands" or "customers"). A detailed case study of industrial significance, highlighting land treatment technology, is included to illustrate the proposed methodology and various process scenarios are evaluated within this case study to demonstrate the general applicability of the proposed optimization program.