Decreasing Seawater Desalination Footprint by Integrating Bipolar-Membrane Electrodialysis in a Single-Pass Reverse Osmosis Scheme

Abstract

Reverse osmosis (RO) is currently the most costefficient method for seawater (SW) desalination; however, producing high-quality water with a low boron concentration typically requires a two-pass process, which increases the required area and chemical consumption. We propose a sustainable and economic pathway for boron removal in a single RO step, thus reducing the area footprint. At the same time, chemicals are produced onsite from the RO brine using bipolar membrane electrodialysis (BMED), thus reducing the chemical footprint. We conducted BMED using natural and synthetic feed solutions and studied the acid and base production kinetics and electricity consumption to assess the feasibility. In terms of energy efficiency, the divalent cationic impurities in the feed are more detrimental than the anionic ones. We found that monoselective cation-exchange membranes are not efficacious in eliminating these, and hence, precipitation/nanofiltration before BMED is essential. As a BMED feed, the nanofiltered SWRO brine was the best option over SW or nanofiltered SW. Economical analysis shows that as compared to purchasing chemicals, BMED integration can reduce the process cost by 45%. In addition, the results point to the flexibility of the proposed design that increases its robustness toward fluctuation in chemicals and electricity prices.

Electrodialysis-Based Recovery of Water and Chemicals in Recycled Polyethylene Terephthalate Industries: Energy, Environmental, and Economic Performance

“…This technology has garnered attention for its versatility. For instance, Chaudhury et al integrated BMED into a seawater desalination process for boron removal and chemical recovery . Monat et al demonstrated that BMED should be a viable approach for cost-efficient and sustainable phosphogypsum processing by converting Na 2 SO 4 to NaOH and H 2 SO 4 for reuse.…”

“…For instance, Chaudhury et al integrated BMED into a seawater desalination process for boron removal and chemical recovery. 12 Monat et al 13 demonstrated that BMED should be a viable approach for cost-efficient and sustainable phosphogypsum processing by converting Na 2 SO 4 to NaOH and H 2 SO 4 for reuse. Nevertheless, the application of BMED for treating brackish wastewater, which typically falls within a conductivity range of 1−10 g/L, has received limited attention in research.…”

Current Density Dependence of Transport Selectivity of Metal Ions in the Electrodriven Process across the Cation Exchange Membrane

“…Selective transport of cations across cation exchange membranes (CEMs) is vital in multiple applications like desalination and energy production by electrodriven transport (ED), reverse electrodriven transport, electrodeionization, capacitive deionization, etc. ,− Transport selectivity (i.e., ability to preferentially transport one cation over another) between multi- and monovalent cations is a prerequisite in processes like water softening, , metal ion extraction, , NaCl production from seawater, , etc., whereas the preferential transport among the monovalent cations is utilized in the process like recovery of Cs + from nuclear waste. , Along with the cationic composition and membrane characteristics, operation parameters are also known to affect the cation transport in CEMs . Therefore, an empirical understanding of the transport phenomena under various working conditions is necessary to improve the process efficiency. , In this regard, the working current/voltage is a crucial parameter in electrodriven processes.…”