Techno-economic analysis of seawater reverse osmosis brines treatment using nanofiltration modelling tools

Abstract

The management of seawater desalination (SWD) brine presents environmental and economic challenges. However, according to the circular economy approach, this residue offers an interesting source of resources. While nanofiltration (NF) has been extensively studied experimentally, few modelling tools exist for scaling up this process due to its performance dependence on solution composition, membrane characteristics, and operational parameters.In this study, the Solution-Electro-Diffusion-Film model was used to conduct a techno-economic analysis for scaling up NF in the treatment of SWD brine, with a focus on resource recovery. Three commercial membranes, NF270, PROXS2, and Fortilife XC-N, were subjected to technical and economic evaluations. Initially, permeate flux, selectivity factors, and scaling potential were determined as a function of applied pressure and permeate recovery. An economic evaluation was conducted considering energy consumption, capital expenditures, and operational expenditures.Results indicated that the NF270 membrane exhibited the highest permeate flux and the lowest rejections, suggesting a low scaling potential. However, this membrane also demonstrated the lowest selectivity factors. In contrast, the PROXS2 and Fortilife XC-N membranes exhibited the highest selectivity factors, particularly at high operational pressures. Regarding economic aspects, it was observed that increasing permeate recovery and reducing pressure led to decrease energy consumption (0.5–1.5 kWh/m3).