A hybrid ion exchange-nanofiltration (HIX-NF) process for energy efficient desalination of brackish/seawater

A new hybrid ion exchange-nanofiltration (HIX-NF) separation process for energy-efficient desalination: Process concept and laboratory evaluation

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.

High recovery rate NF–FO–RO hybrid system for inland brackish water treatment

BackgroundAs an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran.MethodsThis study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl−1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied.ResultsResults showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91.ConclusionsComparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process.The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na.

The nanofiltration (NF) process becomes the most recently used technologies for the desalination of seawater and brackish water. The porous media transport properties are first related to the geometrical complexity of the product. However, the membrane transport models used in desalination process constitute approximatively the less understood process. The objective of this work is to address modeling and numerical study of the desalination process of the water and ions fluxes by using a porous membrane with nanoparticles. Our filtration system used is constituted by two different zones that the membrane sheets are sandwiched. The fluid undergoes a first simple filtration and a second NF process by the injected nanoparticles. The impacts of the permeability K and porosity S of the membrane under the effect of a pressure [Formula: see text] were discussed. Our findings are obtained in the framework of the dynamic Langevin approach based on the competitiveness between the stochastic process and dissipation. The results show that the performance of the rejection membrane is significant as the nanoparticle concentration decreases, and increases as a power law with the ratio of the viscosity of the salty fluid to the pure fluid.

Desalination of brackish water by nanofiltration and reverse osmosis

A novel chitosan (CS)-piperazine (PIP) composite nanofiltration (NF) membrane with satisfied characteristics for brackish water and seawater desalination was successfully developed. PIP was mixed with CS during the interfacial polymerization (IP) process to enhance the NF membrane permeate flux. The resultant NF membranes were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), contact angle. Effects of CS concentration, trimesoyl chloride (TMC) concentration, reaction time and the mixing ratio of CS/PIP on NF membrane performance were investigated thoroughly. When PIP in the aqueous phase monomers reached to 25% (w/w), the PWF (60.6 L·m−2·h−1) was synergistically improved by nearly 2 times without a significant reduction of Na2SO4 rejection (89.1%). Moreover, the NF membranes possessed excellent performance for the desalination of brackish water and seawater, which showed high potential to be applied in the desalination process for water treatment.

Fouling of high pressure-driven NF and RO membranes in desalination processes: Mechanisms and implications on salt rejection

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

Nanofiltration (NF) membranes have applications in several areas. One of the main applications has been in brackish and sea water treatment for drinking water production as well as for wastewater treatment. NF can either be used to treat all kinds of water including ground, surface, and wastewater or used as a pre treatment for desalination. The introduction of NF as a pre treatment is considered a breakthrough for the desalination process. NF membranes have the ability to remove turbidity, hardness, fluoride and nitrate as well as a significant fraction of dissolved salts. Desalination can be performed with a significantly lower operating pressure and becomes a much more energy‐efficient process. NF membrane transport properties, process prediction and modeling are very important. The ability to predict the performance of NF processes will allow for a reduce number of experiments, saving money and helping to understand the NF separation mechanisms. Several studies have investigated the partial and selective demineralization induced by NF. New methods were suggested to minimize and to control the brine disposal in brackish and sea water treatment. The paper will also address the application of NF for water treatment and as a pre‐treatment step for low energy consumption processes such as photovoltaic‐powered units.

A novel nanofiltration membrane with a sacrificial chlorine-resistant nanofilm: Design and characterization of tailored membrane pores and surface charge

In this study, the applicability of nanofiltration (NF) membranes as a pretreatment prior to reverse osmosis (RO) in seawater desalination was investigated. The membranes used wereNF270 and NF90 as the NF membranes, while the brackish water (BW) RO membrane BW30 was used as the RO membrane. In desalination tests, permeates of the NF membraneswere collected and used as the feed to the BW30 membrane. The calculated permeate fluxes were 6.7 L/h.m2, 11.3 L/h.m2, 24.3 L/h.m2, and 36.6 L/h.m2 for single BW30-35 bar,NF270-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar and NF90-30 BW30-35 bar, respectively. The calculated water recovery and rejected salt values were 51.6%, 41.4%,24.8%, 15.4% and 98.2%, 98.2%, 96.0%, 91.0% for NF90-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar, NF270-30 bar + BW30-35 bar and single BW30-35 bar, respectively.The qualities of the product waters of integrated systems (NF+BWRO) and the single BWRO system were also investigated. Boron rejection was fairly well with average boronrejections of 59.3% and 60.2% by NF90-30 bar + BW30-25 bar and NF90-30 bar + BW30-35 bar combinations, respectively while single BW30-35 bar gave an average rejection of49.6%. The results obtained showed that the quality of product water obtained using single BWRO did not comply with the irrigation standards, while the integrated systems providedtotal compliance to irrigation standards with the exception of boron.

A combined ion exchange–nanofiltration process for water desalination: III. Pilot scale studies

Surface-engineered sulfonation of ion-selective nanofiltration membrane with robust scaling resistance for seawater desalination

Water is the most common substance in the world, however, 97% is seawater and only 3% is fresh water. The availability of water for human consumption is decreasing due to increasing the environmental pollution. According to the World Health Organisation (WHO), about 2.4 billion people do not have access to basic sanitation facilities, and more than one billion people do not have access to safe drinking water (Singh, 2006). Moreover, the world’s population is expected to rise to nine billion from the current six billion in the next 50 years. Chronic water pollution and growing economies are driving municipalities and companies to consider the desalination as a solution to their water supply problems. Generally, desalination processes can be categorized into two major types: 1) phasechange/thermal and 2) membrane process separation. Some of the phase-change processes include multi-stage flash, multiple effect boiling, vapour compression, freezing and solar stills. The pressure driven membrane processes, such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF), have found a wide application in water treatment (Charcosset, 2009). The energy required to run desalination plants remains a drawback. The energy limitations of traditional separation processes provided the impetus for the development and the commercialisation of membrane processes. Membrane technologies (simple, homogenous in their basic concepts, flexible in application), might contribute to the solution of most of the existing separation problems. Nowadays, membranes are used for the desalination of seawater and brackish water, potable water production, and for treating industrial effluents. RO membrane separation has been traditionally used for sweater desalination (Charcosset, 2009; Schafer et al., 2005; Singh, 2006). One of the limitations of membrane processes is severe loss of productivity due to concentration polarisation and fouling or scaling (Baker & Dudley, 1998; Schafer et al., 2005). Membrane pretreatment processes are designed to minimise the potential problems of scaling resulting from the precipitation of the slightly soluble ions. Membrane (MF or UF) pretreatment of RO desalinations plants is now a viable options for removing suspended solids, fine particles, colloids, and organic compounds (Banat & Jwaied, 2008; Singh, 2006). NF pretreatment of sweater is also being used to soften RO feed water instead of traditional softening (Schafer et al., 2005). The industrial development of new membrane processes, such as membrane distillation (MD), is now being observed (Banat & Jwaied, 2008; Gryta, 2007). In MD process feed water is heated to increase its vapour pressure, which generates the difference between the partial