Removal of boron from seawater by selective ion exchange resins

Reverse osmosis (RO) desalination process is an efficient and reliable membrane technology for the production of drinking water from seawater. However, some serious limitations had recently been discovered during the field practice. Boron problem is one of them. According to the WHO regulations, the boron concentration should be lower than 0.5 mg/L in drinking water. It is still difficult to reduce boron level to 0.5 mg/L or lower with the conventional reverse osmosis desalination plants equipped with commercially available RO membranes. Therefore, more efficient separation technologies are needed for boron removal.In this study, the performance of the boron-selective ion exchange resins containing N-methyl glucamine groups, as Diaion CRB 02 and Dowex XUS 43594.00, have been tested for boron removal from model seawater. The kinetic performances of these resins were compared. The kinetic data obtained were evaluated using Lagergren pseudo-first-order and second-order models. Also, the process kinetics were predicted by using diffusion models. In addition, column-mode tests have been carried out for boron removal from model seawater.     

Boron in seawater and methods for its separation — A review

The seawater reverse osmosis (SWRO) membrane desalination process is a relevant and reliable technology for desalination of seawater. However, some serious limitations had recently been discovered during field practice, among them the boron problem seems to have a critical meaning. According to the WHO regulations, the boron concentration should be reduced to less than 0.5 mg/L for drinking water. It was also reported that, this limit is rarely reached for conventional reverse osmosis desalination plants equipped with commercially available membranes. This paper reviews the extensive published literature on separation methods of boron removal from seawater.     

A new methodology for removal of boron from water by coal and fly ash

High levels of boron concentrations in water present a serious problem for domestic and agriculture utilizations.The recent EU drinking water directive defines an upper limit of 1 mgB/l. In addition, most crops are sensitive to boron levels >0.75 mg/1 in irrigation water. The boron problem is magnified by the partial (∼60%) removal of boron in reverse osmosis (RO) desalination due to the poor ionization of boric acid and the accumulation of boron in domestic sewage effluents. Moreover, high levels of boron are found in regional groundwater in some Mediterranean countries, which requires special treatment in order to meet the EU drinking water regulations. Previous attempts to remove boron employed boron-specific ion-exchange resin and several cycles of RO desalination under high pH conditions. Here, we present an alternative methodology for boron removal by using coal and fly ash as adsorbents. We conducted various column and batch experiments that explored the efficiency of boron removal from seawater and desalinated seawater using several types of coal and fly ash materials under controlled conditions (pH, liquid/solid ratio, time of reaction, pre-treatment, regeneration). We examined the effect of these factors on the boron removal capacity and the overall chemical composition of the residual seawater. The results show that the selected coal and fly ash materials are very effective in removing boron such that the rejection ratio of boron can reach 95% of the initial boron content under certain optimal conditions (e.g., pH = 9, L/S = , reaction time > 6 h). Our experiments demonstrated that use of glycerin enables regeneration of boron uptake into coal, but the boron uptake capacity of fly ash reduces after several cycles of treatment-reaction. The boron removal is associated with Mg depletion and Ca enrichment in the residual seawater and conversely with relative Mg enrichment and Ca depletion in the residual fly ash We propose that the reaction of Ca-rich fly ash with Mg-rich seawater causes co-precipitation of magnesium hydroxide in which boron is co-precipitated. The new methodology might provide an alternative technique for boron removal in areas where coal and fly ash are abundant.     

Optimization of seawater RO systems design

The paper describes the configuration and operating parameters of current large seawater desalination systems.Major advances of RO seawater desalination technology that lead to a remarkable decrease of desalted water costs are evaluated. Process improvements that enable compliance with more stringent requirements of permeate water quality are discussed. Results of field tests conducted to demonstrate a new process approach are described. Some examples of process optimization resulting in lower power consumption and more efficient system operation are presented.     

Distillation vs. membrane filtration: overview of process evolutions in seawater desalination

The worldwide need for fresh water requires more and more plants for the treatment of non-conventional water sources. During the last decades, seawater has become an important source of fresh water in many arid regions. The traditional desalination processes [reverse osmosis (RO), multi stage flash (MSF), multi effect distillation (MED), electrodialysis (ED)] have evoluated to reliable and established processes; current research focuses on process improvements in view of a lower cost and a more environmentally friendly operation. This paper provides an overview of recent process improvements in seawater desalination using RO, MSF, MED and ED. Important topics that are discussed include the use of alternative energy sources (wind energy, solar energy, nuclear energy) for RO or distillation processes, and the impact of the different desalination process on the environment; the implementation of hybrid processes in seawater desalination; pretreatment of desalination plants by pressure driven membrane processes (microfiltration, ultrafiltration and nanofiltration) compared to chemical pretreatment; new materials to prevent corrosion in distillation processes; and the prevention of fouling in reverse osmosis units. These improvements contribute to the cost effectiveness of the desalination process, and ensure a sustainable production of drinking water on long terms in regions with limited reserves of fresh water.     

压力交换式能量回收器在反渗透海水淡化技术中的应用

在反渗透海水淡化系统中，高压系统中采用压力交换式能量回收器，大大地降低海水淡化的能耗。压力交换式能量回收器的能量回收效率达到95％以上，本文从其工作原理和反渗透海水淡化设计上阐述其应用的优点。     

用海水淡化法解决海岛用水

我国多数海岛属于资源性缺水，解决用水困难的途径有两条，海底管道从大陆调水和海水淡化就地制水。文章详细分析了影响反渗透海水淡化成本的诸因素，对不同生产容量反渗透海水淡化工厂的投资及生产成本进行了预测。针对舟山某岛群的地理条件对海底管道引水和就地海水淡化制水进行了综合比较。最后提出解决该岛用水短缺的可行方案。     

Hybrid systems in seawater desalination—practical design aspects, present status and development perspectives

Ever since seawater desalination has been applied on an industrial scale, and particular in the countries of the Arabian Gulf, the application of desalination processes in dual-purpose facilities—water and power—as a hybrid configuration has been discussed in many feasibility investigations and also planning concepts. It is above all the combination of reverse osmosis with thermal processes that has found increasing interest with the aim of ensuring, as economically as possible, uniform water supplies under the specific, greatly varying load conditions in the Gulf countries. Such design concepts for hybrid configurations encompass straightforward structures with a low degree of coupling between membrane and thermal desalination processes, but range up to very complex configurations with strong interconnections on both the water side and thermally, as well as with several desalination processes connected in series or in parallel. Classical hybrid concepts in which the permeate from an RO desalination component is mixed with distillate from thermal desalination have already been implemented in Saudi Arabian dual-purpose plants, like Jeddah and Yanbu-Medina. Although hybrid systems of greater complexity have been addressed in many design studies and publications, up to now none has been brought to fruition. Coming into consideration asthe design basis for determining the capacity shares of the various desalination processes operated in a hybrid configuration are: arrangement of thermal cycle of the power plant component; water/power ratio of the dual-purpose seawater desalination and power plant; provision of undiminished water production of the desalination plant as electricity generation varies; provision of a specified drinking water quality with regard to composition and salt content; combination of all these aspects. Also gaining in importance are concerns of environmental pollution and sustainable development when selecting seawater desalination and power plant configurations, as well as their optimization when considering desalination and electricity generation as a whole. In the practical design of hybrid membrane and thermal systems, aspects come to light, though, that restrict linking of the two systems and joint utilization of facilities, as conceived in studies and conceptual design investigations. This applies both for common utilization of intakes and the use of heated up cooling water from thermal processes as a feed stream for the RO part of the desalination process. Additionally, requirements of drinking water composition, particularly chloride content, TDS and compliance with a specific residual content of boron, influence specifically the design of the membrane process part and its share in the total desalination capacity. Such practical aspects have greatly influenced the design and configuration of the Fujairah hybrid plant for which, from a total desalination capacity of 100 MIGD (454,600 m³/d), the share of 37.5 MIGD (170,500 m³/d) makes its seawater RO plant the biggest currently being constructed anywhere in the world. From the findings of the engineering of this plant and the idea that, by increasing interconnection between the two processes on the water side, it is possible to advance a hybrid configuration of this type with regard to cost optimization in the membrane installation, but also by joint utilization of the intake equipment, perspectives result for applied research efforts over the near and long terms, for example: long-term behavior of membranes at elevated temperatures; tendency for biofouling in membrane process with common utilization of cooling water and brine; influences of such interconnections on the overall availability of the facility. But also for the operation and maintenance organization of such large facilities, consequences can be foreseen for the future development of hybrid plants, particularly for operation management and organisation of the interplay of the different power plant and desalination systems, monitoring of SWRO membrane replacement and cleaning, as well as controlling water quality.     

Reliability of the jeddah seawater RO desalination plant based upon operations experience

Demand on commercial RO seawater desalination plants can be assured with increase in reliability and with high levels of performance. Such improvements can best be achieved through “lessons learned” from experience gained in available RO systems such as the large Jeddah RO plant.In this study, critical components which affect plant performance have been identified and methods of improving the design have been recommended. Failure data has been extracted from operation and maintenance reports.An assessment is made of the impact of failures and outages on the availability of the RO desalination plant. The single largest influence on the effective capacity of a water supply system based on RO desalination of seawater is found to be plant availability and maintainability. The design configuration of the plant is also found to have an impact on the acceptability of water supply system performance.     

A comparative study for boron removal from seawater by two types of polyamide thin film composite SWRO membranes

In this paper, field performance of a small-scale seawater reverse osmosis unit installed in Urla Bay-Izmir, Turkey was analyzed and presented. The design of SWRO system in Urla consists of two types of FilmTec polyamide thin film composite spiral wound seawater reverse osmosis membranes (high rejection FILMTEC XUS SW30XHR-2540 RO membrane and FILMTEC SW30-2540 RO membrane) which could be operated in parallel. To make a comparative study between two types of membranes regarding their desalination performances and boron rejections, each membrane was operated individually for each set of experiments. This comparison was made via investigation of the effects of feed seawater temperature (10–16 °C), operating pressure (55, 60 and 62 bar), and pH adjustment on the feed side (pH 7.0–7.5).     

风电-海水淡化联合系统中脱硼技术方案选择

该文针对风电海水淡化联合系统的主要特点及特殊要求,通过对国内外海水脱硼技术的研究分析,结合实际工程经验,提出了适合该系统不同制水规模的脱硼方案,为风电-海水淡化联合系统的推广应用提供有益参考。     

Polymer-based chelating adsorbents for the selective removal of boron from water and wastewater: A review

Boron removal from water is a highly interesting research area that has been addressed in various investigations in the recent years. This is due to the expansion of harmful effects of boron traces in water streams on the environment and human health with the rise in boron global demand in various industries that coincided with the implantation of more stringent water quality standards. Various technologies have been applied for the removal of boron from water solutions, including ion exchange technology, which has a great potential in treating varieties of boron-containing streams up to levels in parts per million using boron-selective adsorbents. This article comprehensively reviews the latest progress in the development of polymer-based boron-selective (chelating) materials and their applications for the removal of boron from water solutions, including commercial boron-selective resins (BSRs) and their researched counterparts. The emerging trends in the development of alternative adsorbents with different substrates, morphologies, and functional groups are also elucidated. The future directions to overcome the limitations of the present generation of resins are also discussed.     

Performance study of water desalination methods in Saudi Arabia

Saudi Arabia is an arid desert country without rivers or sweet water lakes, however, it does have vast amount of groundwater and seawater. In order to make these waters suitable for human consumption and industrial use, most of their salts must be removed by some means. The desalination methods most frequently used in the Kingdom are: Multistage flash (MSF) evaporation, reverse osmosis (RO), and electrodialysis (ED).During the last decade, we have witnessed a spectacular growth of desalination plants. This growth is expected to continue in the next decade. The present production capacity of all desalting plants in Saudi Arabia is estimated to be 750,000 m³/day; this figure will be most likely tripled in the next five years.This paper is a report on a performance study of the most significant desalination plants in the Kingdom. The plants, which include MSF and seawater and brackish water RO plants, were selected either because of their size or their importance to the desalination technology. The plants are briefly described and their performances are discussed.     

High recovery system in seawater reverse osmosis plants

Seawater desalination by the reverse osmosis (RO) method is an energy-saving system compared with the evaporating method, and can perform seawater desalination efficiently. Seawater RO desalination technology has been established and become a reliable system. Seawater desalination plants using RO technology have spread and the scale of the plants has increased significantly. More economical and efficient RO method seawater desalination systems have come to be required. A high recovery system, which offers reduction of plant construction cost and running cost was devised. Towards realization of this high recovery system, simulation and the field tests were done to confirm the practicality. Furthermore, a high recovery system was adopted for the biggest desalination plant in Japan, and it is performing favorably. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Non-equilibrium sorption modeling for boron removal from geothermal water using sorption-microfiltration hybrid method

In this study, the boron removal performance of a hybrid system composed of ground ion exchange resin particles coupled with a microfiltration separation unit was investigated. A non-equilibrium sorption modeling approach was introduced so as to understand the contributions of mass transfer resistances on the effluent stream concentration profiles, as well as on the resin loading scheme of this sorption-microfiltration hybrid system. This modeling approach allowed us to suggest new system operations and/or scale-up processes of sorption-microfiltration hybrid systems. In this study, the highly porous crosslinked boron selective chelating resins Diaion CRB02 and Dowex XUS 43594.00 containing N-methyl-glucamine group were used. Geothermal water that has high levels of boron was fed into the stirred cell element of the microfiltration system. Kinetic behaviour of boron selective resins for boron removal from geothermal water by the microfiltration system was evaluated to investigate the effects of resin particle size, resin concentration, and permeate flow rate.     

高回收率反渗透海水淡化工艺

目前反渗透海水淡化的回收率小于40％。本文研究开发死端超滤预处理技术和反渗透一纳滤联合脱盐相结合的膜集成海水淡化新工艺,与传统工艺比较,具有装置体积小,产水回收率高等优点。文章介绍了采用新工艺的海水淡化装置样机的试制情况及现场运行结果。沿岸海水为料液,操作压力1为5．1MPa条件下,操作压力2为2.0MPa条件下,装置脱盐率99．21％,产水量3971.3L/h,产水回收率55％。海水淡化装置对海水中Ca^2 、Mg^2 、Na^ 、HCO3^-、Cl^-、SO4^2-、TDS,总碱度,总硬度的脱除率分别为99％,99．6％,99．21％,95％,99．35％,98．48％,99.21％,95％,99．42％。     

Membrane processes for water supply and reuse - a question of energy consumption and cost

This paper is limited primarily to reverse osmosis which is the dominating membrane process in commercial plants. Desalination of brackish water and seawater with reverse osmosis, with special emphasis on costs and energy consumption, is the primary subject discussed in the paper. Some aspects of and development trends in industrial and domestic applications of membrane processes are also taken up, particularly with regard to by-product recovery and water reuse in connection with advanced wastewater treatment.The first RO plant to be brought into operation in Riyadh, Saudi Arabia, is located at Salbukh. The investment and total operation costs for this plant have been calculated in the paper. The water cost is at least twice as high as in a continental U.S. location. The main reason for this is the very high cost of civil and local works in Saudi Arabia. A similar calculation has been made for RO seawater desalination.Increased energy costs during the last decade have directed research and development work for all desalination methods towards reducing energy consumption. It is shown in the paper that energy recovery in connection with RO seawater desalination is particularly feasible. Different methods for energy recovery have been investigated and reported, the preferred methods depending on the size of the RO plant. A large underground RO plant for energy recovery, based on utilization of the static pressure instead of high pressure pumps, has also been studied.Another possible energy-saving, but also water quality improving method has been proposed, viz . a combined MSF-RO dual purpose plant. Excess power for reverse osmosis seems to be more and more available in Saudi Arabia due to the high power/water ratio in MSF dual purpose plants compared to the real demand for power and water.     

Complexation-Enhanced Boron Removal in a Dual-Stage Nanofiltration Seawater Desalination Process

A complexation-enhanced boron removal method in a dual-stage nanofiltration (NF) seawater desalination process was investigated. A comparative experiment of five different polyols was carried out. Sorbitol was chosen as the complexation additive because of its higher equilibrium constant. The reaction between boron and sorbitol was rapid and only slightly affected by the other ions. Due to the complexation reaction, boron rejection of dual-stage NF seawater desalination process was increased from 35% to 62% in the first stage and from 42% to 55% in the second stage. Boron concentration reached 0.1 mg/L by adjusting the complexation and pH value. Molecular structures were simulated using the molecular simulation technology. The results indicated that molecular structure and molecular size played significant roles in enhancing boron removal. Meanwhile, NaOH and sorbitol had no evident effect on the chemical structure of the membrane surface. The results indicated that complexation is an effective method to reduce boron concentration in a dual-stage NF seawater desalination process.     

集成膜工艺海水淡化与浓海水综合利用

综述了反渗透一电渗析集成工艺海水淡化与浓缩水综合利用研发现状与发展趋势。指出具有特殊分离功能的离子交换膜电渗析技术是高度分离、富集海洋化学元素的关键技术。提出了目前需要研究的几个问题。     

Evaluation of an ion exchange system regenerated with seawater for the increase of product recovery of reverse osmosis brackish water plant

An experimental ion exchange unit was operated on the Red Sea shore. Softening of the reject containing 1,400 ppm calcium from a nearby RO brackish water plant was performed using seawater as regenerant. The ex- perimental results reported show that the calcium concentration in the softened reject was reduced to a level which enables further RO desalting of the reject at 50% product recovery. A preliminary economic evaluation of 4,000m³/day RO plant indicates that desalting of softened reject would be more economically advantageous than the continued operation of the existing thermal seawater desalting plants and should precede the commercial RO seawater desalting at this location.