Towards Macroscopic Water Integration for Zero Liquid Discharge in Industrial Complexes

Abstract

The increasing environmental pressures to minimize wastewater discharge from industrial plants to the environment have led to the emergence of policies and regulations that promote Zero-Liquid Discharge (ZLD) solutions. These systems are typically associated with high capital and operating cost and pose a significant economic burden to implementing industries. ZLD solutions are explored as End-of-Pipe treatment options to eliminate liquid discharges. Instead, ZLD options should be explored in the context of overall water integration of industrial facilities to achieve desired reductions in water footprints through efficient reuse together whilst achieving ZLD.

In this work, we propose a systematic approach to screen sustainable and low cost strategies that will assist in targeting water integration for Zero Liquid Discharge (ZLD) in industrial parks. The approach expands an Eco-Industrial Park (EIP) representation for water integration to include different possible ZLD options. A mixed integer non-linear programming (MINLP) model for water integration in industrial parks is developed to screen the representation. The optimization model represents a decision support tool that can help the designer in quickly evaluate potential reuse and recycle scenarios with ZLD. The model is formulated to allow streams to be reused internally and externally in each plant, recycled in a shared centralized and decentralized treatment and in ZLD systems, and utilized for a number of options that can constitute ZLD including beneficial usage and/or ZLD processing. The default objective is to achieve ZLD at minimum total annual cost.

A case study of an industrial park with three plants has been solved and analyzed in a number of scenarios to illustrate the usefulness of the proposed model.