4735722 Desalination of seawater or brackish water

Both brackish water desalination and seawater desalination processes are well established and in common use around the globe to create new water supply sources. The farther the location of the source water from the ocean or seashore, the lower the salinity (TDS) of the water and the lower the osmotic pressure that needs to be overcome when desalinated water is produced. This is one of the major reasons that brackish desalination is often considered less costly than seawater desalination. A number of project considerations, however, indicate that seawater desalination can be beneficial and more cost-effective than brackish water desalination. To make a fair comparison, we need to properly compare all major aspects of both types of projects to define the best and most appropriate desalination technology. While brackish water has less feed water TDS, it is more challenging to dispose of the produced concentrate. Also, although brackish water desalination needs less energy to overcome osmotic pressure, it usually requires more energy to draw the water from the well than it takes to pump seawater from the open ocean intake. Another factor is that the temperature of the brackish well water may be lower than the temperature of ocean water, giving seawater desalination an advantage in energy demand. In comparing brackish to seawater desalination, these major aspects should be evaluated: (1) Locations of seawater and brackish water plants, relative to the major consumers of the desalinated water, (2) Transportation (pumping and disposal) costs of the feed water and produced water, (3) Potential colocation of a seawater plant with a large industrial user (e.g., power plant) of the seawater for cooling or other purposes, (4) Produced quality of brackish water and seawater desalination in terms of major minerals and emerging contaminants, (5) Sustainability of the water source: capacity and depth of the brackish water wells, as well as the type of soil. (6) Technical and economic aspects of produced concentrate disposal, (7) Permitting process costs for brackish and seawater desalination, and (8) The economics of both brackish and seawater desalination treatment processes: capital costs, operational and maintenance (O&M) costs, lifetime water cost, and total water cost (TWC). This paper discusses the major evaluation criteria and considerations involved in properly comparing the economic and technical aspects of brackish and seawater desalination to determine the more favorable desalination technology for a given desalination project.

Desalination and disinfection of inland brackish ground water in a capacitive deionization cell using nanoporous activated carbon cloth electrodes

Brackish water desalination using reverse osmosis and capacitive deionization at the water-energy nexus

Desalination of brackish water by nanofiltration and reverse osmosis

Desalination of high salinity brackish water by an NF-RO hybrid system

The role of desalination in bridging the water gap in Jordan

Analysis of desalination alternates for phosphoric acid plant in Tunisia

A methodology to investigate brackish groundwater desalination coupled with aquifer recharge by treated wastewater as an alternative strategy for water supply in Mediterranean areas

The desalination of brackish ground water using cascade Rankine cycle is proposed. A pair of a Rankine cycle like steam Rankine cycle (SRC) and organic Rankine cycle (ORC) as a waste heat recovery. The single stage steam turbine for the SRC unit while the scroll expander for ORC unit is selected. Simulation of cascade RO system performance is considered using R245fa as a working fluid for ORC unit. The saturated steam from solar Scheffler disc will expand into steam turbine, where the reject heat from steam turbine will utilize for evaporation of ORC working fluid. The high-pressure RO pumps integrated with SRC and ORC turbines to provide net driving pressure to the RO module. This type of system is well suitable for desalination of brackish water due to moderate working temperature & pressure. Result shows that the pair of Rankine cycle will increase the overall (cascade) efficiency of the system. The basic input parameters are optimised with Taguchi approach. The performance of the system shows a good agreement with variation of mass flow rate of the steam in which the permeate flow rate from RO will increase along with the cycle efficiencies.

Flow-electrode capacitive deionization (FCDI) is an emerging electrochemically driven technology for brackish and/or sea water desalination with merits of large salt adsorption capacity, high flow efficiency, and easy electrode management. While FCDI holds promise for continuous operation, there are very few investigations with regard to the regeneration/reuse of flowable electrodes and the separation of brine from electrodes with these operation prerequisites for real nonintermittent water desalination. In this study, we propose a novel module design to achieve these critical steps involving integration of an FCDI cell and a ceramic microfiltration (MF) contactor. Our investigations reveal that the brine discharge rate is the dominant factor for stable and efficient operation of the integrated module. Results obtained show that the integrated FCDI/MF system can be used to successfully separate brackish water (of salinities 1, 2 and 5 g L-1) into both a potable stream (<0.5 g L-1) and a brine stream (concentrated by 2-20 times) in a continuous manner with extremely high water recovery rates (up to 97%) and reasonable energy consumption. Another notable characteristic of the integrated system is the high thermodynamic energy efficiency (∼30%) with such efficiencies 4-5 times larger than those of conventional capacitive deionization units and comparable to reverse osmosis and electrodialysis systems achieving similar separation efficiencies. In brief, the results of studies described here indicate that continuous and efficient operation of FCDI is a real possibility and pave the way for scale-up of this emerging technology.

Carbon aerogel its fabrication and characterization and its uses in this process were studied for desalinating of saline and brackish water. The carbon aerogel manufacturing process involves the polymerization and pyrolysis of the mixture of resorcinol and formaldehyde. Carbon aerogels were analyzed using BET, BJH, and T-plot after construction. The effect of various parameters (including the influent salt concentration, the intensity of electric current flow, the distance between the electrodes and pH) on salt adsorption were studied. Analysis of BET/BJH shown that the surface of aerogel was 677.8 m2/g. much of porosity in the samples of carbon aerogel were between 1-2 nm, namely micro-pour and a similar level 0f 456 m2/gr is dedicated to micro-pour, with a correlation coefficient (r) equal to 94.5. According to the results, it seems that carbon aerogel electrodes have a good structure in desalination of brackish and saline water.

In order to meet people's increasing demand for water, it is urgent to transform undrinkable water resources such as seawater and brackish water into water suitable for human use. Membrane distillation has become a water treatment technology with great development potential due to its advantages of high desalination rate, good water quality, high water recovery and low operating cost. It can effectively solve the problem of desalination of seawater and brackish water, and has broad application prospects in solving the shortage of fresh water resources. However, membrane fouling and polarization effect limit the performance of membrane distillation in seawater desalination. This paper briefly describes the working principle of membrane distillation technology, analyzes the formation mechanism of polarization effect and membrane fouling, and introduces the technical methods for enhancing the performance of membrane distillation. In addition, the future research direction of membrane distillation is prospected.

High water recovery is crucial to inland desalination but is impeded by mineral scaling of the membrane. This work presents a two-step modification approach for grafting high-density zwitterionic pseudo-bottle-brushes to polyamide reverse osmosis membranes to prevent scaling during high-recovery desalination of brackish water. Increasing brush density, induced by increasing reaction time, correlated with reduced scaling. High-density grafting eliminated gypsum scaling and almost completely prevented silica scaling during desalination of synthetic brackish water at a recovery ratio of 80%. Moreover, scaling was effectively mitigated during long-term desalination of real brackish water at a recovery ratio of 90% without pretreatment or antiscalants. Molecular dynamics simulations reveal the critical dependence of the membrane's silica antiscaling ability on the degree to which the coating screens the membrane surface from readily forming silica aggregates. This finding highlights the importance of maximizing grafting density for optimal performance and advanced antiscaling properties to allow high-recovery desalination of complex salt solutions.

Although current water desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. It is well-known that polymer hydrogel network has the ability to absorb water via swelling. In the case of polyelectrolyte hydrogels, the charges localized on the polymer chains, which mainly drive the swelling pressure inside the hydrogel, can also separate added salt via charge-based selectivity (Donnan exclusion). When combining this material with a temperature-sensitive polymer, the heat generated by solar energy can trigger the desorption process via conformational change of polymer chains. Hence, hydrogels designed from both materials, polyelectrolyte and thermo-responsive polymer can reduce the salinity of water, such as brackish water by means of reversible thermally-induced absorption and desorption desalination processes. In addition, the desorption process can also be achieved based solely on a polyelectrolyte hydrogel system by altering the ionization of charges within the hydrogel via pH. In this thesis, hydrogel-based water desalination process were developed using acrylic acid (AAc)/sodium acrylate (SA)-based polyelectrolytes as the charge-based separation function, alone or with a combination of N-isopropylacrylamide (NIPAAm) as thermo-responsive comonomer. In the latter case, a series of chemically cross-linked polymeric hydrogels were synthesized via either free radical-initiated copolymerization or reversible addition-fragmentation chain transfer (RAFT) polymerization, thus realizing different macromolecular architecture. According to the nature of hydrogels, the reversible sorption/desorption state were triggered by either chemical stimulus (pH), or physical stimulus (heat) as the thermo-responsive polymer introduced into the hydrogels. In detail, the effect of hydrogel composition as well as the influence of the macromolecular architecture on the swelling/deswelling behavior for the synthesized hydrogels were studied. For this, their properties including their responses to external stimuli were investigated, and their ability to desalinate brackish water as well as the effciency of such desalination process were evaluated. Generally, the results demonstrated correlations between macromolecular architecture of the network structure and their performance in the proposed desalination process, such as salt rejection and desalination capacity. Moreover, the potential of the best performance materials for applications was also discussed.

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