Interplant Water Networks Coupled with Two-Stage Treatment and ZLD Options
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2017 Elsevier B.V. Zero Liquid Discharge (ZLD) systems are being implemented by many industrial processes, primarily for end-of-pipe treatment, due to severe regulations put into practice for industrial wastewater discharge. A ZLD system mainly involves the use of advanced treatment methods, through which industrial brine wastewater is essentially reduced to dry solids/salts. When closely observing standard wastewater treatment technologies, conventional systems often result in brine waste, towards the very end of all processing stages. Brine may then be transformed into salts/bitterns via additional brine-to-salt processing, by incorporating ZLD techniques. Some ZLD technologies may result in the recovery of additional water streams alongside the process. Since ZLD systems can be integrated onto interplant water network systems either as central or distributed units, assessing the presence of both scenarios allow for cost-optimal designs to be identified. In addition, any water streams recovered in conjunction with ZLD processing must be appropriately accounted for. Hence, this work attempts to integrate ZLD processing options onto a previously developed representation for interplant water network design (Alnouri et al., 2014; Alnouri et al., 2015). To facilitate the quantification of brine-to-salt processing, all wastewater treatment options have been represented using two distinct stages: Stage 1 consists of treatment options that result in no brine discharge, while Stage 2 involves treatment options that achieve contamination removal in the form of a brine wastewater stream. Cutting down brine discharge may be achieved by sending brine wastewater streams produced by Stage 2 treatment units for further ZLD processing. In order to illustrate the proposed approach from a water network design perspective, a case study which compares the network performance achieved with and without the integration of ZLD options, is presented.