Block and falling film freeze concentration are two technologies that separate water by freezing,with the
potential to desalinate seawater. In this study, the
integration of two freeze concentration techniques as
an alternative to obtain potable water was analysed.
Water with 0.5%–8% NaCl was freeze-concentrated by
the falling film technique. The ice from each stage was fractionally thawed to recover the solids retained in
Marangoni hydrodynamic motion and its potential technological application in reverse osmosis (RO) process for seawater desalination is discussed. The fundamental core idea in this note is the possibility to take advantage of the inherent concentration gradient in a RO process. It is well known that to run a RO process, it is necessary to apply a hydrodynamic pressure to overcome the osmotic pressure, however, by inducing a free-surface, e.g., a Leidenfrost surface, on the membrane wall, an additional hydrodynamic Marangoni stress could be generated, which, likewise than the osmotic pressure is driven by the concentration gradient but acting in the opposite direction, i.e., reducing the external hydraulic pressure to be applied. Utilizing a simplified geometrical and physical model, an analytical expression for the pressure reduction was derived. One important preliminary result in this work, is that the Marangoni stress can provide pressure against the osmotic pressure for membrane porous that are less than micrometric size.
The Campo de Cartagena (Eastern Spain) is one of Europe’s driest areas with a mean precipitation of around 300 mm. One of the main challengesin the region is to secure a reliable water supply in both quantity and quality terms, to provide a water supply and agricultural irrigation, while water desalination has become an extensively applied solution, and one of the most sustainable solutions to the water scarcity problem. As water availability is lacking and groundwater quality is poor, the agricultural sector in Campo de Cartagena has developed small private brackish groundwater desalination plants (15-20 m3/h) through already existing agricultural wells. Costs and benefits (C-B) for citrus cultivation (1 ha) in three such plants have been assessed. The results indicate that for the studied cases, current agricultural management is feasible and costs outweigh benefits, with a positive NPV and a cost/benefit ratio higher than 1. The internal rate of return is also positive and higher than 11%. The results evidence practical and theoretical implications as to how to increase water resources in areas where water is scarce by closing the loop, ensuring farmers’ profitability and encouraging private sector investments.
This paper presents results on simulation, optimization and control of hybrid solar based energy system to power a desalination plant. The principal objective is to design a clean energy system to meet the desired electric load of the desalination plant with high renewable fraction, low cost of energy, and low carbon dioxide gas emissions. Hourly simulations and optimization were performed to determine the performance and life cycle cost of the different hybrid power configurations. The results of the baseline or the actual power system from the grid are compared with two new renewable power systems: (1) grid tied solar system: solar PV/grid/inverter power system, and (2) Off grid solar power system: PV/diesel generator/battery/inverter power system. The results show that the solar PV/grid/inverter power system offers the best performance compared to PV/diesel generator/battery/inverter. The total energy from the hybrid grid tied solar system is used to meet the AC load of the desalination plant with almost no excess electricity and power shortage. The proposed hybrid power system for the desalination plant is sustainable, economically viable and environmentally friendly: high renewable fraction (47.3%), low excess power (0.15%), low levelized cost of energy (90$/MWh), and low CO2 gas emissions (264.25kgCO2/MWh).
Water scarcity in the Mediterranean basin has been solved by using seawater desalination reverse osmosis technology (SWD-RO). This technology produces brine which is discharged back into the sea resulting in an environmental impact on marine ecosystems. Under the circular economy approach, the aim of this work is to recover resources from NaCl-rich brine (~60-70 g/L), e.g. in the form of NaOH and HCl, by integration of two ion exchange-based membrane technologies and quantify the electrical energy consumption. Electrodialysis (ED) incorporating monovalent selective cation exchange membranes as divalent ions purification and concentration of the NaCl present in the SWD-RO brine, was integrated with bipolar membrane ED (EDBM) to produce NaOH and HCl. Current densities of 0.30–0.40 kA/m2 at two temperature ranges simulating different seawater temperature regimes (15-18 ºC and 22-28ºC) were tested and a pure NaCl solution was used as starting concentrate stream. NaCl-rich brines with 100 or 200 gNaCl/L were obtained by ED and then introduced in the EDBM stack producing HCl and NaOH up to 2 M, depending on the initial concentrations. A minimum energy consumption of 1.7 kWh/kgNaOH was calculated when working by EDBM with initial concentrations of 104 g NaCl/L and 0.24 M HCl and NaOH.
Chemical industries generate large amounts of wastewater rich in different chemical constituents. Amongst these, salts at high concentrations are of major concern, making necessary the treatment of saline effluents before discharge. Because most of these rejected streams comprise a combination of more than one salt at high concentration, it is reasonable to try to separate and revalorize them to promote circular economy at industry site level. For this reason, ion-exchange membranes based technologies were integrated in this study: selectrodialysis (SED) and electrodialysis with bipolar membranes (EDBM). Different process brines composed by Na2SO4 and NaCl at different concentrations were treated first by SED to separate each salt, and then by EDBM to produce base (NaOH) and acids (HCl and H2SO4) from each salt. The optimum of both electrolyte nature and concentration of the SED stack streams was evaluated. Results indicated that it was possible to separate Cl- and SO42- depending on the anionic membrane, initial electrolytes and concentrations of each stream. Pure NaOH and a mixture of HCl and H2SO4 with different purities could be obtained. Energy consumption evolutions were plotted and an optimal zone work was found where the consumption values were acceptable.
Nanofiltration (NF), as a selective Mg(II) and Ca(II) separation and concentration treatment, and electrodialysis with bipolar membranes (EDBM) were evaluated for the valorization of seawater desalination reverse osmosis brines (60 NaCl/L) to produce both rich Mg(II) and Ca(II) brines for phosphate recovery and HCl and NaOH as chemicals for desalination treatments. A NF pilot plant, using NF270 membranes at 20 bar, provided a rich Mg(II) (8.3 g Mg(II)/L) and Ca(II) (2.1 g Ca(II)/L) brine on the concentrated stream with enrichment factors of 3.2 for Mg(II) and 2.5 for Ca(II). The NF permeate stream containing 50 ± 2 g NaCl/L was treated to remove residual Mg(II) (760 mg/L) and Ca(II) (415 mg/L) by chemical precipitation with Na2CO3 and NaOH before the EDBM unit. Divalent cations free brine containing NaCl (50 g NaCl/L) were fed into the EDBM stack in order to produce NaOH and HCl under recirculation configuration. Constant voltage and acid and base concentrations at different initial conditions were evaluated to obtain the maximum acid and base concentration (approximately 1 M NaOH/HCl) at 9 V. No substantial effect of initial acid and base concentrations on the overall performance was observed. An energy consumption of 2.6 kWh/kg NaOH and current efficiency of 77 ± 3% were calculated
In this work, novel monovalent selective cation exchange membranes (CEMs) with different mixtures of polyvinylidene fluoride (PVDF) and sulfonated PVDF (S-PVDF) were synthesized. The selected composite membranes were modified by surface polymerization of polyaniline (PANi) to improve their monovalent cation selectivity. PANi was doped with p-toluene sulfonic acid (pTSA) or L-valine (2-amino-3-methylbutanoic acid) and the selectivity of each CEM was determined. Membrane properties, such as chemical composition, water uptake, ion exchange capacity, permselectivity, contact angle and crystallinity were measured. The influence of the applied voltage was also studied. The newly developed membranes were used for electrodialytic concentration of NaCl from synthetic reverse osmosis (RO) brine. Doped membranes with pTSA (S-Na(Mg) = 0.13, S-Na(Ca) = 3.59) and valine (S-Na(Mg) = 0.09, S-Na(Ca) = 0.8) have a higher selectivity for sodium than the composite ones (S-Na(Mg) = 0.63, S-Na(Ca) = 6.82). Moreover, the increase of applied voltage results in an increase of the selectivity for monovalent ions. (C) 2015 Elsevier B.V. All rights reserved.
The salt discharged from reverse osmosis is concentrated by ion-exchange membrane electrodialysis to produce salt for industrial use and the salt concentration is reduced to seawater level for preventing environmental impact on marine ecosystems. The technology was evaluated experimentally and discussed with a computer simulation program of the electrodialysis system incorporated with U shape cells. The algorithm computes mass transport, energy consumption, electric current leakage, concentrate NaCl purity, pressure drop and limiting current density. The seawater reverse osmosis discharged brine was supplied to the electrodialysis pilot plant and it was operated changing current density and temperature taking benefit of seasoning variations. The computed energy consumption E-Nacl and NaCl concentration in concentrated solutions C-NaCl '' using developing algorithms provided a good description of the experimentally measured values with correlation coefficients of R(r) = 0.9 for E-NaCl and R(r) = 0.6 for C-NaCl ''. Then the reasonability of the developed algorithms is supported by the experimental set of data. The current leakage is nearly 3% for any electric current. The pump driving force is very low. The limiting current density is very high. In order to decrease salt concentration at the outlets of desalting cells to seawater level, it is necessary to increase desalting ratio to 0.5. This technique however increases Emu and decrease C-NaCl ''. In spite of this operating circumstance, E-NaCl and C-NaCl '' are comparable to the data in the salt manufacturing plant operation to produce edible salt. NaCl produced from in the reverse osmosis discharged brine electrodialysis is competitive in the edible salt market. (C) 2015 Elsevier B.V. All rights reserved.
Bisphenol A (BPA) is a typical Endocrine Disrupting Chemical (EDC), which is potentially harmful during wastewater reclamation. In this study, its degradation during Fenton's process under different operational conditions was investigated in combination with subsequent nanofiltration of low concentration remnant BPA and compounds derived from oxidation. The results indicate that BPA could be degraded efficiently in aqueous phase by Fenton, even at very low hydrogen peroxide doses. The treatment of up to 300 mg/L solutions of BPA with Fenton liquor at optimal conditions resulted in its complete removal in less than 2 min. The optimal conditions were found to be pH, = 3, H2O2/BPA = 020 and Fe2+/BPA = 0.012. Five NF polymeric membranes having different properties were used for the nanofiltration of treated and non-treated solutions. The nanofiltration of BPA solutions showed that rejection is related to adsorption ability of BPA on the membrane and size exclusion mechanism. In the nanofiltration of the effluent after Fenton oxidation, high TOC, COD, colour and Fe2+ (>77%) removal were achieved, although significant membrane fouling was also observed. The normalised water flux after membrane flushing with water was lower than 60% in almost all used membranes, which indicates significant non-easily removable fouling. (C) 2014 Elsevier B.V. All rights reserved.
High concentration of chloride ions in continental water is a great problem for the exploitation of these natural resources. In industry, the use of this water involves additional conditioning steps. For drinking water and irrigation uses, the Cl- must be reduced by conventional water treatment processes, like ion exchange or reverse osmosis, but for large scale production these techniques could be very expensive due to resin regeneration or energy costs. The possibility of using supported liquid membranes (SLM) with ionic liquids (IL), Aliquat 336, Cyphos IL 101 and Cyphos IL 167, as carriers to exchange Cl- for HCO3- anion has been shown to work. The reversibility of this anion exchange was corroborated by solvent extraction experiments and implemented in flat sheet supported liquid membrane (FSSLM) and hollow fiber renewal liquid membrane technologies (HFRLM). About double transport values have been obtained in HFRLM compared to SLM and 1 h is the time enough to reduce the chloride concentration up to 250 mg/L using HFRLM at the best experimental condition. The results obtained allow us to be optimistic about the implementation of this technology on a large scale to chloride reduction in drinking water when the source is inadequate for direct use. (C) 2013 Elsevier B.V. All rights reserved.
Reig, M.; Casas, S.; Aladjem, C.; Valderrama, C.; Gibert, O.; Valero, F.; Miguel, C.; Larrotcha, E.; Cortina, J. Desalination Vol. 342, p. 107-117 DOI: 10.1016/j.desal.2013.12.021 Data de publicació: 2014-06-02 Article en revista
Currently, numerous studies are focused on the valorisation of seawater desalination reverse osmosis brines. Electrodialysis can be used to concentrate one of the primary components (NaCI) and obtain a suitable raw material for industrial applications, such as the chlor-alkali industry. An electrodialysis pilot plant was used to evaluate the efficiency of concentrating a seawater reverse osmosis (SWRO) brine under representative full-scale operational conditions covering the temperature range of a semiarid climate. The results indicate that electrodialysis is a technology that can concentrate SVVRO brines from approximately 70 to 245 g/L NaCl, achieving an additional intrinsic purification of major multivalent ions (Ca2+, Mg2+, SO42-) due to the selectivity patterns of ion exchange membranes and the ion-complexation reactions in the concentrated brines. However, minor components, such as Ni and Cu, are concentrated due to the formation of Cu and Ni complexes with chloride ions to form monocharged species (e.g., NiCl+ and CuCl+). Energy consumption values of 0.12 kWh/kg NaCl for 185 g NaCl/l at 27 degrees C and 0.35 kA/m(2) or 0.19 kWh/kg NaCl for 203 g NaCl/l at 27 degrees C and 0.50 kA/m(2) were reached. These results were compared with the data obtained from the literature for salt production by electrodialysers. (C) 2013 Elsevier B.V. All rights reserved.
Oatley, D.; Llenas, L.; Aljohani, N.H.M.; Williams, P.; Martinez, X.; Rovira, M.; De Pablo, J. Desalination Vol. 315, p. 100-106 DOI: 10.1016/j.desal.2012.09.013 Data de publicació: 2013-04-15 Article en revista
Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. There is a real need to determine a suitable description for dielectric exclusion for use in membrane modelling for the ab initio design and development of new membrane separation processes and for the scale up and optimisation of existing processes.
In this paper the currently accepted separation mechanisms of membrane nanofiltration are explored in order to justify the use of porous models. Furthermore, the Desal-5-DK membrane is characterised by performing a series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point. This has the advantage of effectively neutralising the membrane fixed charge and facilitating an independent study of the dielectric partitioning at the membrane surface. A simplistic model based on Born theory was tested and found to be remarkably accurate, indicating that ion solvation may be the appropriate dielectric exclusion mechanism for true nanofiltration membranes
Valderrama, C.; Ribera, G.; Bahí, N.; Rovira, M.; Giménez, T.; Nomen, R.; Lluch, S.; Yuste, M.; Martinez, X. Desalination Vol. 306, p. 1-7 DOI: 10.1016/j.desal.2012.08.016 Data de publicació: 2012-11-15 Article en revista
Valderrama, C.; Gibert, O.; Arcal, J.; Solano, P.; Akbarzadeh, A.; Larrotcha, E.; Cortina, J. Desalination Vol. 279, num. 1-3, p. 445-450 DOI: 10.1016/j.desal.2011.06.035 Data de publicació: 2011-09-15 Article en revista
The main interest of the methodology for the investigation of wastewater reclamation and reuse systems which
is proposed in this paper is that all costs and benefits (social and private) are considered in the economic and technological
analysis. This general concern allows an improvement in the design of investment decisions.
Traditionally, an economic-financial analysis of wastewater reclamation and reuse systems focuses exclusively
on the study of costs and private benefits. The methodology that is presented in this paper takes into account
not only the private impacts but also the project spillovers which could have relevance on the project.
In this research, the use value of the reclaimed water in the Natural Wildlife Park of Aiguamolls de l’Emporda`
is estimated. The travel cost technique is applied to estimate the external value of the Park. According to the final
results, the price of the reclaimed water in the Park should have to be between 0.75 ⁄/m3 (without opportunity
cost) and 1.20 ⁄/m3(with opportunity cost).
Supported liquid membranes (SLMs) have demonstrated all along the years every high selectivity in facilitated transport of metal ions, however, they have some well known limitations, such as the gradual loss of the organic phase to the aqueous solutions. This paper describes two different types of novel membranes developed for the general purpose of separating and concentrating metal ions of interest in order to improve SLM physical and chemical characteristics. Both hybrid (organic—inorganic) membranes and activated composite membranes have been tested for the selective transport of Zn/Cd and Pt/Pd mixtures. For this purpose, different carriers have been used: 2-ethylhexyldithiophosphoric acid and 2-ethylhexylphosphoric acid for the separation of Zn and Cd whereas Aliquat 336 for Pt/Pd mixtures. The choice of these metal couples is related to environmental detoxification and catalyst recovery, respectively.