Desalination Of Brackish Groundwater Research Articles

DesaLink: solar powered desalination of brackish groundwater giving high output and high recovery

Desalination of groundwater is essential in many arid areas that are far from both seawater and fresh water resources. The ideal groundwater desalination system should operate using a sustainable energy source and provide high water output per land area and cost. To avoid discharging voluminous brine, it should also provide high recovery. To achieve these aims, we have designed DesaLink, a novel approach to linking the solar Rankine cycle to reverse osmosis (RO). To achieve high recovery without the need for multiple RO stages, DesaLink adopts a batch mode of operation. It is suited to use with a variety of solar thermal collectors including linear Fresnel reflectors (LFR). For example, using a LFR occupying 1,000 m2 of land and providing steam at 200°C and 15.5 bar, DesaLink is predicted to provide 350 m3 of fresh water per day at a recovery ratio of 0.7, when fed with brackish groundwater containing 5,000 ppm of sodium chloride. Here, we report preliminary experiments to assess the feasibility of the concept. We study the effects of longitudinal dispersion, concentration polarisation and describe a pilot experiment to demonstrate the batch process using a materials testing machine. In addition, we demonstrate a prototype of DesaLink running from compressed air to simulate steam.

Comparison of Configurations for High-Recovery Inland Desalination Systems

Desalination of brackish groundwater (BW) is an effective approach to augment water supply, especially for inland regions that are far from seawater resources. Brackish water reverse osmosis (BWRO) desalination is still subject to intensive energy consumption compared to the theoretical minimum energy demand. Here, we review some of the BWRO plants with various system arrangements. We look at how to minimize energy demands, as these contribute considerably to the cost of desalinated water. Different configurations of BWRO system have been compared from the view point of normalized specific energy consumption (SEC). Analysis is made at theoretical limits. The SEC reduction of BWRO can be achieved by (i) increasing number of stages, (ii) using an energy recovery device (ERD), or (iii) operating the BWRO in batch mode or closed circuit mode. Application of more stages not only reduces SEC but also improves water recovery. However, this improvement is less pronounced when the number of stages exceeds four. Alternatively and more favourably, the BWRO system can be operated in Closed Circuit Desalination (CCD) mode and gives a comparative SEC to that of the 3-stage system with a recovery ratio of 80%. A further reduction of about 30% in SEC can be achieved through batch-RO operation. Moreover, the costly ERDs and booster pumps are avoided with both CCD and batch-RO, thus furthering the effectiveness of lowering the costs of these innovative approaches.

Using capacitive deionisation for inland brackish groundwater desalination in a remote location

In this work, a portable prototype of capacitive deionisation (CDI) unit has been used first time in Wilora, a community in a remote area in Northern Territory, Australia, to remove salt from the brackish groundwater. The CDI unit has demonstrated sufficient salinity and hardness removal ability at the remote brackish water source. It was found that increased flow rate resulted in a decrease of the overall total dissolved solids removal efficiency. However, in terms of energy efficiency, a higher flow rate tended to be favourable. With the current CDI unit configuration and local water conditions, 7L/min is recommended as the optimal operational parameter, with an energy consumption of around 1.89kWh/m3 of treated water. The total water recovery rate was between 75 and 80%. The electrosorption of NaCl onto the CDI cell assembly of 100 pair electrodes follows Langmuir adsorption isotherm and the pseudo-first-order adsorption kinetics. The portable CDI unit proves to be a viable alternative solution to brackish water treatment, especially in communities in remote areas where building a reverse osmosis treatment plant is not practical. The data and results shown in this work can be used as guidance for the on-site operation using this emerging technology.

Energy Footprint analysis of brackish groundwater desalination with zero liquid discharge in inland areas of the Arabian Peninsula

Semi-arid regions throughout the world face water scarcity and the need for more efficient and alternative sources of drinking water supply. Inland regions in the Arabian Peninsula have the alternate option of coastal seawater desalination and long-distance conveyance, often with lift to substantial elevation. In several aquifers of this region, naturally occurring radium in groundwater is above acceptable standards and must be reduced.We analyzed the energy footprint of a modular process employing a combination of pellet reactor for radium and hardness minimization, reverse osmosis with intermediate precipitation, and concentrated brine crystallization to achieve high recovery with zero liquid discharge (ZLD). Pilot tests demonstrate technical viability of the selected processes to achieve high recovery, radium and hardness reduction, and over 95% salinity reduction with zero liquid discharge. The results indicate that the energy usage per unit volume of water produced from groundwater is consistently lower than coastal seawater desalination, regardless of the conveyance distance. The substantial reduction of energy, higher recovery and minimized residual discharge of this process are also beneficial to the environment when compared to conventional processes currently being used. The results may be applicable and beneficial to other regions with similar conditions.

Vibratory shear enhanced process (VSEP) for treating brackish water reverse osmosis concentrate with high silica content

In this study, a vibratory shear enhanced process (VSEP) was used to treat the concentrate generated from a spiral wound reverse osmosis (RO) system and increase the overall feed water recovery during brackish groundwater desalination. The feed water recovery of the spiral wound RO system was restricted to less than 75% due to silica polymerization on the membrane surface. Due to the high shear rate generated near the membrane surface by the VSEP system, high fluxes (50 – 100 Lm-2h-1) were achievable. Although silica levels exceeding 240mg/L were present in the spiral wound RO concentrate, deposition of colloidal silica was restricted on the VSEP membrane surface. But, the VSEP system did not prevent the precipitation of barium sulfate and required frequent chemical cleaning. Utilization of antiscalants and lowering of initial specific flux did not result in reducing the scaling potential but implementation of continuous crossflow operation resulted in a lower rate of specific flux decline. The rejection property of the VSEP system for ions, metals and organics was comparable to a spiral wound RO system. By using a VSEP system to treat spiral wound RO concentrate, the overall feed water recovery of the desalting process was enhanced.

Application of membrane processes in drinking water treatment–state of art

Membrane technology is widely accepted as a means of producing various qualities of water from surface water, well water, brackish water and seawater. In the treatment of water for drinking purposes first of all pressure-driven membrane techniques are used. The choice of the suitable membrane process depends on the size of the removed contaminants and admixtures from the water. Desalination of seawater and brackish groundwater is often the way to obtaining drinking water. Significant improvements in technology and design of reverse osmosis, the availability of alternative energy sources, the possibility of pretreatment and applied materials have caused the process to become environmentally-friendly source of fresh water in many regions of the world, particularly in those where their sources are limited. Nanofiltration and to some extent the reverse osmosis are the methods of water softening, as well as to remove disinfection by-products precursors and micropollutants. To remove inorganic micro-pollutants ...

Improved aquifer characterization and the optimization of the design of brackish groundwater desalination systems

Many water scarce regions possess brackish-water resources that can be desalted to provide alternative water supplies. Brackish groundwater desalination by reverse osmosis (RO) is less expensive than seawater systems because of reduced energy and pretreatment requirements and lesser volumes of concentrate that require disposal. Development of brackish groundwater wellfields include the same hydraulic issues that affect conventional freshwater wellfields. Managing well interference and prevention of adverse impacts such as land subsidence are important concerns. RO systems are designed to treat water whose composition falls within a system-specific envelope of salinities and ion concentrations. A fundamental requirement for the design of brackish groundwater RO systems is prediction of the produced water chemistry at both the start of pumping and after 10–20 years of operation. Density-dependent solute-transport modeling is thus an integral component of the design of brackish groundwater RO systems. The accuracy of groundwater models is dependent upon the quality of the hydrogeological data upon which they are based. Key elements of the aquifer characterization are the determination of the three-dimensional distribution of salinity within the aquifer and the evaluation of aquifer heterogeneity with respect to hydraulic conductivity. It is necessary to know from where in a pumped aquifer (or aquifer zone) water is being produced and the contribution of vertical flow to the produced water. Unexpected, excessive vertical migration (up-coning) of waters that are more saline has adversely impacted some RO systems because the salinity of the water delivered to the system exceeded the system design parameters. Improved aquifer characterization is possible using advanced geophysical techniques, which can, in turn, lead to more accurate solute-transport models. Advanced borehole geophysical logs, such as nuclear magnetic resonance, were run as part of the exploratory test well program for a new 66,200 m3/d (17.5 million US gal/d, MGD) brackish-water desalination plant for the City of Hialeah, Florida. Salinity and hydraulic conductivity data from the borehole logging program were used for both well design (determination of production zone) and groundwater modeling to optimize the production wellfield layout and predict future water quality. Advanced characterization techniques have general applicability for improving the design and predictability of well-based raw water supply systems, including alternative seawater intakes.

Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: general framework

Semi-arid coastal zones often suffer water-stress, as water demand is high and markedly seasonal, due to agriculture and tourism. Driven by scarcity of surface water, the communities in semi-arid coastal regions turn to aquifers as prime water source; but intensive exploitation of coastal aquifers causes seawater intrusion, which degrades the quality of groundwater. The cost-efficient and sustainable development of coastal aquifers can be achieved through a holistic management scheme which combines two non-traditional water sources: (a) saltwater, to be treated to the desired quality, and (b) wastewater, to be re-claimed to augment aquifer recharge for control of seawater intrusion, and also to meet certain demands. This management scheme is based on the idea that it is cost-advantageous to: (i) desalt brackish groundwater, instead of seawater, as the former requires far less energy, and (ii) to re‐use wastewater at only the differential cost to any treatment already practiced. In this paper, we present the general framework of the proposed management scheme, and a decision aid tool (DAT) which has been developed to assist decision makers to explore the scheme's decision space. The DAT uses cost as optimization criterion to screen various management scenarios, via modelling of the dynamic natural-engineered system behaviour, and identifies those cost-efficient ones that meet the water demand and achieve aquifer protection. Citation Koussis, A. D., Georgopoulou, E., Kotronarou, A., Lalas, D. P., Restrepo, P., Destouni, G., Prieto, C., Rodriguez, J. J., Rodriguez-Mirasol, J., Cordero, T. & Gomez-Gotor, A. (2010) Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: general framework. Hydrol. Sci. J. 55(7),1217–1233.

Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: application to the Akrotiri basin and aquifer, Cyprus

We investigate the general methodology for an intensive development of coastal aquifers, described in a companion paper, through its application to the management of the Akrotiri aquifer, Cyprus. The Zakaki area of that aquifer, adjacent to Lemessos City, is managed such that it permits a fixed annual agricultural water demand to be met, as well as and a fraction of the water demand of Lemessos, which varies according to available surface water. Effluents of the Lemessos wastewater treatment plant are injected into the aquifer to counteract the seawater intrusion resulting from the increased pumping. The locations of pumping and injection wells are optimized based on least-cost, subject to meeting the demand. This strategy controls sea intrusion so effectively that desalting of only small volumes of slightly brackish groundwater is required over short times, while ∼2.3 m3 of groundwater is produced for each 1 m3 of injected treated wastewater. The cost over the 20-year period 2000–2020 of operation is ∼40 M€ and the unit production cost of potable water is under 0.2 €/m3. The comparison between the deterministic and stochastic analyses of the groundwater dynamics indicates the former as conservative, i.e. yielding higher groundwater salinity at the well. The Akrotiri case study shows that the proposed aquifer management scheme yields solutions that are preferable to the widely promoted seawater desalination, also considering the revenues from using the treated wastewater for irrigation. Citation Koussis, A. D., Georgopoulou, E., Kotronarou, A., Mazi, K., Restrepo, P., Destouni, G., Prieto, C., Rodriguez, J. J., Rodriguez-Mirasol, J., Cordero, T., Ioannou, C., Georgiou, A., Schwartz, J. & Zacharias, I. (2010) Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: application to the Akrotiri basin and aquifer, Cyprus. Hydrol. Sci. J. 55(7), 1234–1245.

Mathematical model of electrodialysis with ion-exchange membranes and inert spacers

A mathematical model describing the two-dimensional concentration field of an electrodialysis device with inert spacers is proposed. The boundary-value problem includes the Navier-Stokes, continuity, and steady-state convective diffusion equations and well-defined conditions and is solved by the control-volume numerical method. Results are expressed in the form of functional relationships of generalized variables. It is shown that when channels of the electrodialysis device are filled with spacers that do not conduct electric current, mass transport increases by several times in comparison to devices with open channels. The possibility is discussed for replacing the inert spacers with ones that conduct ion, not only in the complete demineralization of natural waters, but also in the desalination of brackish ground waters.

Development of an integrated reverse osmosis-greenhouse system driven by solar photovoltaic generators

The development of a system that integrates reverse osmosis (RO) with a horticultural greenhouse has been advanced through laboratory experiments. In this concept, intended for the inland desalination of brackish groundwater in dry areas, the RO concentrate will be reduced in volume by passing it through the evaporative cooling pads of the greenhouse. The system will be powered by solar photovoltaics (PV). Using a solar array simulator, we have verified that the RO can operate with varying power input and recovery rates to meet the water demands for irrigation and cooling of a greenhouse in north-west India. Cooling requires ventilation by a fan which has also been built, tested and optimised with a PV module outdoors. Results from the experiments with these two subsystems (RO and fan) are compared to theoretical predictions to reach conclusions about energy usage, sizing and cost. For example, the optimal sizing for the RO system is 0.12–1.3 m2 of PV module per m2 of membrane, depending on feed salinity. For the fan, the PV module area equals that of the fan aperture. The fan consumes <30 J of electrical energy per m3 of air moved which is 3 times less than that of standard fans. The specific energy consumption of the RO, at 1–2.3 kWh ?m-3, is comparable to that reported by others. Now that the subsystems have been verifi ed, the next step will be to integrate and test the whole system in the field.

Desalination and Long-Haul Water Transfer as a Water Supply for Dallas, Texas: A Case Study of the Energy-Water Nexus in Texas

As existing water supplies become increasingly strained in some locations, water planners turn to alternative options to quench cities’ thirst. Among these options for inland cities is desalination of seawater or brackish groundwater with long-haul water transfer. Desalination using reverse osmosis membranes is the most common technology in use, yet high pressures required for operation make desalination an energy-intensive water supply option. The subsequent conveyance of desalinated water through long-haul pipelines also requires large amounts of energy. To analyze desalination and long-haul transfer as a drinking water supply, Dallas, Texas, was chosen as a test-bed with two scenarios: seawater desalination near Houston and brackish groundwater desalination near Abilene, both with long-haul transfer of desalinated water to Dallas. Combining the energy requirements for long-distance pumping with the energy demands for desalination, we estimate that desalination and long-haul transfer is nine to 23 times more energy-intensive per unit of water than conventional treatment of local surface water sources, an increase of 230 to 630 MWh/d for 20 million gal (75,700 m3). These results suggest that desalination and long-haul transfer as a water supply for Dallas is less sustainable, based on energy consumption, than use of local surface water sources or water conservation. Citation: Stillwell AS, King CW, Webber ME. 2010. Desalination and long-haul water transfer as a water supply for Dallas, Texas: A case study of the energy-water nexus in Texas. Texas Water Journal. 1(1)33-41. Available from: https://doi.org/10.21423/twj.v1i1.1042.

Desalination of brackish groundwater by direct contact membrane distillation

The direct contact membrane distillation (DCMD) applied for desalination of brackish groundwater with self-made polyvinylidene fluoride (PVDF) membranes was presented in the paper. The PVDF membrane exhibited high rejection of non-volatile inorganic salt solutes and a maximum permeate flux 24.5 kg m(-2) h(-1) was obtained with feed temperature at 70 degrees C. The DCMD experimental results indicated that the feed concentration had no significant influence on the permeate flux and the rejection of solute. When natural groundwater was used directly as the feed, the precipitation of CaCO(3) would be formed and clog the hollow fibre inlets with gradual concentration of the feed, which resulted in a rapid decline of the module efficiency. The negative influence of scaling could be eliminated by acidification of the feed. Finally, a 250 h DCMD continuous desalination experiment of acidified groundwater with the concentration factor at constant 4.0 was carried out. The permeate flux kept stable and the permeate conductivity was less than 7.0 microS cm(-1) during this process. Furthermore, there was no deposit observed on the membrane surface. All of these demonstrated that DCMD could be efficiently used for production of high-quality potable water from brackish groundwater with water recovery as high as 75%.

Innovative Technologies Increase Evaporation Pond Efficiency

Desalination of brackish groundwater is an increasingly important option for inland communities. However, disposing of concentrated saline residual waste streams in evaporation ponds is land intensive. Large facilities might be concerned that this technology is one of the few treatment methods that offers decreasing returns to scale because of increasing boundary-layer resistance for larger ponds. This study evaluated several innovative options for improving evaporation pond performance, including fabric evaporators, wetted-boundary layer breakers, salt-tolerant plants, and droplet spraying. Cost models were developed for boundary-layer breakers and droplet spraying. Incremental costs and evaporation enhancements are compared with site-specific cost information for a wastewater treatment facility in California's Central Valley. Results indicate that boundary-layer breakers and spray technologies are cost-effective compared to a simple pond expansion. Boundary-layer breakers appear to be more cost-effective per gal of incremental capacity but have a lower evaporation enhancement capacity compared to droplet spraying (24 percent vs. 35 percent). For a new facility, an example calculation with preliminary cost information indicates that spray evaporation is more cost-effective because of avoided pond excavation and lining costs. Boundary-layer breakers as a retrofit to an existing facility are preferred if they provide sufficient additional capacity to avoid the need for pond expansion.

Innovation and Energy Savings Prove a Great Idea for Oxnard Desalting Facility

This article discusses the Groundwater Recovery and Treatment (GREAT) program used by the city of Oxnard, California to manage community water resources as an integrated, fully functioning regional water supply system. The concept behind the program was to reduce the need for imported water by creating facilities that can use local brackish groundwater resources, and thus reduce dependence on costly imported water supplies. The GREAT program links all the water resources in the Oxnard Plain – including imported water, local groundwater, wastewater, recycled water, and brine wastes – and delineates how each resource can be used for maximum benefit to the Oxnard area. Under the program, highly treated recycled water will be delivered to agricultural and industrial customers currently using groundwater for nonpotable purposes. In winter, when irrigation needs are low, recycled water will be used to recharge groundwater aquifers and help prevent saltwater intrusion in coastal wells. Desalination of brackish groundwater will allow the city to continue providing high‐quality drinking water while reducing reliance on imported water. The article discusses the advanced energy‐efficient treatment technology used by the Oxnard desalination plant that eliminates inefficient series pumping, reduces the size of the building required, and removes the need for noise reduction in the facility. Additionally, the design of each of the three Oxnard reverse osmosis (RO) units incorporated an interstage boost/energy‐recovery turbine. The design of the Oxnard facility incorporates principles and elements of the U.S. Green Building Council's Leadership in Energy and Environmental Design Initiative, and the facility's numerous green building elements are listed.

Considering Reverse Osmosis and Electrodialysis Reversal for Desalination of Brackish Groundwater Containing High Silica

Brackish water desalination is an important alternative for developing drinking water sources in arid regions. Electrodialysis reversal (EDR) and reverse osmosis (RO) are suitable technologies for desalination of brackish groundwater. Pilot testing conducted with brackish groundwater containing 1,200 mg/L of total dissolved solids (TDS) and 60 mg/L of silica demonstrated that RO can operate at 10 gfd with 75 percent recovery and 96 percent TDS rejection. As predicted by modeling software for the same water chemistry, the EDR process can operate at 88 percent recovery with TDS rejection of 78 percent. Order of magnitude cost estimates (−30 percent and +50 percent) prepared for three feed-flow scenarios (3, 5, and 8 mgd) for RO and EDR treating the same groundwater suggested both processes are comparable, especially when feedwater contains elevated silica levels.

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Reducing the environmental impacts of reverse osmosis desalination by using brackish groundwater resources

The aim of the present work is to find out whether or not, and to what extent, the environmental impacts of reverse osmosis desalination are reduced when brackish groundwater is used instead of sea water. In order to answer this question, the Life-Cycle Assessment (LCA) methodology is used, and two water production plants are compared. The brackish groundwater scenario is based on a plant located in Almería (southern Spain), while the sea water scenario is based on literature data. Four impact categories and two environmental indicators, one of them related to brine discharge, are included. The results show that the key life-cycle issue of brackish groundwater desalination is electricity consumption, and since this is substantially reduced with regard to using sea water, the life-cycle impacts are found to be almost 50% lower. An uncertainty analysis based on Monte-Carlo simulation shows that these environmental savings are significant for all impact categories. Potential local impacts provoked by brine discharge are also found to be lower, due to a reduced content of salts. It is concluded that, when and wherever possible, exploitation of brackish groundwater resources should be assigned priority to sea water resources as an input for reverse osmosis desalination, although it must be taken into account that groundwater, as opposed to sea water, is a limited resource.

Brackish groundwater treatment by nanofiltration, reverse osmosis and electrodialysis in Tunisia: performance and cost comparison

The possibility of producing drinking water from brackish groundwater using nanofiltration (NF), reverse osmosis (RO) and electrodialysis (ED) processes was studied. Brackish groundwater samples were taken from the south of Tunisia (Gabes and Zarzis cities), and characterized in terms of pH, conductivity, hardness and inorganic matters. The results obtained in this work show that nanofiltration permits to reduce the concentrations of Ca 2+, Mg 2+ and SO 4 2−, which are responsible for elevated sulfate hardness. The total dissolved salts of the produced water is equal to 1890 mg.l −1. This is higher than the maximum value for drinking water fixed by the WHO at 500 mg.l −1. Desalination of brackish groundwater by RO or ED might be technically and economically viable to cope with water scarcity and overcome the water deficit in Tunisia. The results showed that RO and ED were actually efficient since they highly reduced the content of inorganic matters present in raw waters. The treatment by RO or ED shows that the concentrations of ions in the obtained permeate (or the diluate) did not exceed the permissible WHO standards. ED seems to be the economical desalination process for Gabes water due to its low energy consumption whereas Zarzis water should be treated with the RO process.

Developing a Protocol to Evaluate New‐generation Membranes for Desalinating Brackish Groundwater

For some water‐scarce regions, desalination of brackish groundwater represents an important alternative resource for water utilities. High‐pressure membranes that use reverse osmosis (RO) and nanofiltration (NF) are recognized as a viable technology for groundwater desalination. Many improvements have been made in membrane production, and new membranes are being rapidly introduced into the market, highlighting the need for standardized evaluation protocols. This article presents a step‐by‐step approach to pilot‐testing new high‐pressure NF and RO membranes. The proposed steps are basic data collection, comparative pilot‐testing, optimization pilot‐testing, membrane autopsy, and feasibility analysis. Within this framework, the article describes the various aspects that must be covered during new‐generation membrane testing at the screening level. In addition, data obtained during pilot‐testing of two new‐generation RO membranes are presented. The pilot tests conducted following this protocol shows clear performance distinctions between an established high‐pressure membrane and a new high‐pressure membrane. Testing also demonstrated that the operating pressures of the new‐generation membranes have been greatly improved, which could lead to substantial operational cost savings. Finally, a preliminary cost analysis revealed that the higher productivity levels of the new membranes could result in power savings of approximately 13% per year.