Comparative Analysis of Conventional and Emerging Technologies for Seawater Desalination: Northern Chile as A Case Study

Abstract

The aim of this work was to study different desalination technologies as alternatives to conventional reverse osmosis (RO) through a systematic literature review. An expert panel evaluated thermal and membrane processes considering their possible implementation at a pilot plant scale (100 m3/d of purified water) starting from seawater at 20 °C with an average salinity of 34,000 ppm. The desalination plant would be located in the Atacama Region (Chile), where the high solar radiation level justifies an off-grid installation using photovoltaic panels. We classified the collected information about conventional and emerging technologies for seawater desalination, and then an expert panel evaluated these technologies considering five categories: (1) technical characteristics, (2) scale-up potential, (3) temperature effect, (4) electrical supply options, and (5) economic viability. Further, the potential inclusion of graphene oxide and aquaporin-based biomimetic membranes in the desalinization processes was analyzed. The comparative analysis lets us conclude that nanomembranes represent a technically and economically competitive alternative versus RO membranes. Therefore, a profitable desalination process should consider nanomembranes, use of an energy recovery system, and mixed energy supply (non-conventional renewable energy + electrical network). This document presents an up-to-date overview of the impact of emerging technologies on desalinated quality water, process costs, productivity, renewable energy use, and separation efficiency.

Reverse Osmosis Concentrate: Physicochemical Characteristics, Environmental Impact, and Technologies

“…Technologies for ROC are classified as conventional or emerging, depending on their scientific and technical development level, and their presence in the market (see Figure 5). Based on the definition of emerging desalination technologies proposed by Saavedra et al [12], the authors propose that emerging technologies for ROC are scientific innovations that generate incentives to invest in ROC treatment. These innovations are based on evolved technologies that improve ROC management strategies (i.e., minimize rejection and/or effluent valorization).…”

“…The main desalination technologies are classified into two groups: thermal and membranes [10,11]. Figure 1 shows the conventional and emerging technologies for desalination, highlighting reverse osmosis (RO) and multi-effect distillation (MED) with 65% and 21% of installed capacity worldwide, respectively [12]. RO dominates the global desalination market [13] due to its systematic decrease in energy consumption, from 20 kWh/m 3 of purified water in the 1970s to 2.5 kWh/m 3 of purified water today [8,14].…”

“…Water moves from the feed (low salt concentration) to the draw solution (high salt concentration) [158,159]. The key benefits of using forward osmosis for ROC treatment are: (1) the low energy consumption that comes with it, (2) that high TDS water can be treated, and (3) the lower fouling propensity of the membranes compared to pressure-driven membrane processes [12,160]. However, water flux can be lower than expected in the forward osmosis process due to the existence of internal concentration polarization [161].…”

“…• Membrane distillation is based on the fundamentals of evaporation, and vapor distillate may be produced by temperature, partial pressure, or vacuum gradients [12]. A gas-liquid interface is created as volatile constituents are transferred through a microporous hydrophobic membrane.…”

“…Under the right conditions, aquaporin forms a water channel that selectively transports water molecules across while excluding ionic species or other polar molecules. Amy et al [13] reported that aquaporin-based biomimetic membranes are being developed as ultrahigh permeability RO membranes; with impregnation of aquaporins into a polymeric matrix, aquaporin can provide water channeling/gating, leading to controlled water permeability and ion selectivity [12]. This technology promises high efficiency in ROC treatment since the movement of water in aquaporins is facilitated by "selective rapid diffusion" and an osmotic gradient.…”