基于太阳能驱动的倒极电去离子淡化苦咸水

采用新型倒极电去离子(EDIR)装置,在浓淡室与极室中均填充离子交换树脂,与恒定直流电压输出的太阳能电池构成"太阳能-EDIR"装置,以模拟苦咸水为处理对象,考察了EDIR的脱盐性能。结果表明,在树脂混床填充、阴阳树脂体积比为4:6及树脂粒径分布为0.45~0.71 mm时,可获得最佳处理效果。对于含4个膜对的1级2段式EDIR装置,在24 V恒定电压驱动及目标脱盐率不低于90%的前提下,处理TDS质量浓度分别为3、4、5 g/L的模拟苦咸水,产水量可相应达到6、5、4 L/h。基于太阳能驱动的小型EDIR装置能够有效地淡化苦咸水,在解决户外、机动式供饮用水方面有良好的应用前景。     

倒极电去离子过程浓缩分离含镍离子溶液

通过在电去离子(EDI)的淡化室和浓缩室中同时填充离子交换树脂而构成频繁倒极电去离子(EDIR)过程,用以解决处理含重金属离子溶液时EDI内部易产生金属氢氧化物结垢的关键难题。以NiSO4溶液为处理对象,采用浓缩水部分循环和浓、淡水流分步切换的运行工艺,利用EDIR单一过程,同步获得了淡化出水的高截留率和浓缩产品水的高浓缩倍数。实验条件下,倒极周期为4h可获最佳分离效果。对于含Ni2+50mg.L-1、pH为3.0的NiSO4溶液,EDIR的淡水出水和浓水出水的Ni2+浓度可分别达到1.5mg.L-1和3961mg.L-1,淡水中Ni2+的脱除率为97%,浓水的浓缩倍数则为79.2,接近理论值。实验范围内,EDIR过程运行稳定,未产生Ni(OH)结垢。     

两种不同电去离子技术处理含铜金属离子废水的研究

研究了倒极电渗析技术(EDIR)和电去离子技术(EDI)过程中淡出水和浓水室的电导率、p H值、铜离子浓度和膜堆电流,以及运行后离子交换膜和树脂的表面形态。结果表明:EDIR运行15 h的淡出水的电导率为30μS/cm,16 h的铜离子去除率为97.2%。EDI过程中15 h淡出水的电导率550μS/cm,16 h的铜离子去除率为77.8%。EDIR使淡出水的电导率降低,铜离子去除率升高。EDIR淡出水的p H值长期维持碱性,EDI淡出水则由碱性变成酸性、再变成碱性。然而,EDIR和EDI过程中浓水室的电导率和p H值基本接近。EDIR降低了膜堆电流、消除了浓水室阴离子交换膜表面氢氧化铜沉淀,抑制了淡水室中混合树脂表面沉淀。本质上,EDIR通过周期性改变淡水室和浓水室的相对数量和离子迁移方向而消除了膜表面氢氧根离子富集,并缓和了树脂表面水解现象,从而改善了EDIR过程的稳定性。     

EDI用于处理含甲酸废水

在工业生产过程中,排放的废水里含有大量的甲酸。本文以含甲酸废水处理为研究对象,采用自主设计的一级一段电去离子膜堆装置,通过考察I-U、pH-U等特征曲线,研究了离子交换膜、离子交换树脂及树脂填充比例、流速等操作条件对膜堆性能的影响。结果表明：采用异相膜和凝胶型树脂、淡室填充100%阴树脂、淡水流速为2.5 L/h的操作条件,可使EDI膜堆效果最佳;不同甲酸浓度对能耗的影响比较小,淡室浓度变化情况基本相同;当淡室甲酸质量分数为1.00%时,EDI膜堆可获得较高的电流并具有较低的耗电量。总结认为该研究结果可为EDI处理甲酸废水工业装置提供设计依据。     

电去离子技术同步纯化和浓缩含镍离子溶液的研究

采用自制微型电去离子膜堆装置,以模拟电镀镍漂洗水为处理对象,基于特征曲线考察确定了工作膜堆电压,并重点研究了淡水室中的树脂比例对过程分离性能的影响.结果表明,阴阳树脂比存在最优值,任一树脂所占比例过高,均会导致膜堆内部结垢,而阴树脂过量时尤为明显.对于含Ni2+质量浓度52mg/L、pH=3的NiSO4溶液,在优选的膜堆电压下,所用阴阳树脂(体积)比为4:6时,淡化出水和浓缩水的Ni2+质量浓度分别达到0.28mg/L和3 407mg/L,浓差大于12 000倍,且过程具有良好的稳定性.     

电去离子运行过程中的结垢问题及其防止措施

在简要介绍电去离子(EDI)基本原理及其应用的基础上,提出了膜堆结垢是EDI应用过程中的主要问题,分析了膜堆结垢的原因及其预防措施,认为有效防止膜堆结垢的关键因素:控制EDI的进水硬度、CO2浓度等合理的预处理工艺;通过极水室和浓水室中填充离子交换树脂降低膜堆电阻的结构设计.     

电去离子法(EDI)处理电镀含铬废水

电去离子法(EDI)是电渗析和离子交换的结合技术.在电渗析淡室中添加离子交换树脂作为阳极室介质,自制了EDI装置,并采用该装置对电镀铬漂洗废水进行处理,研究了进水pH、流量和电流密度对EDI分离效率的影响.结果发现,当进水pH=4.8,流量和电流密度分别为4 L/h和1.2 mA/cm2时,Cr(VI)的分离效率可达99.5％,但淡室出水中的Cr(Ⅵ)浓度略高于国家排放标准.作为一种能够高效分离电镀铬漂洗废水中六价铬的新技术,EDI仍有一些问题需要解决.     

1种简易电去离子装置的建立及对含Cu~(2+)废水的处理

基于自制板柱结构电去离子装置,探讨了浓水室填充离子交换材料(树脂、离子交换织物)处理低Cu2+含量废水的效果。经过100h运行结果发现,在浓水室中填充离子交换材料能够促进离子迁移,提高电去离子能力和出水水质,同时可缓解阴离子交换膜浓室侧表面的沉淀现象;更长时间运行后也发现,阴离子交换膜和树脂的季铵盐基团转变为叔胺基团,催化水解反应,加剧了离子交换膜和树脂表面沉淀结垢,使电去离子效果恶化。     

回收重金属废水用电去离子技术研究进展

电去离子(EDI)技术是由电渗析和离子交换相互有机结合的膜分离脱盐技术.其具有连续运行、不用酸碱、环境友好等显著优点.作者介绍了国内外采用电去离子技术回收含铜和含镍废水的研究进展,针对重金属废水的特点,设计了以阳树脂为主的阴、阳树脂分层填充的电去离子装置,采用该技术代替传统的离子交换技术,可实现重金属废水的回收和利用.达到闭路循环、零排放、无污染的目的.     

电去离子新技术及其制备注射用水的可行性分析

采用国产化材料组建电去离子(EDI)膜堆,并对EDI膜堆结构进行改造,在其浓水室填充离子交换树脂。试验研究表明,二级EDI膜堆与一级EDI膜堆比较,适应性强、产水水质好且在较短的时间内就基本达到稳定。二级EDI膜堆运行电流控制在2～3 A条件下,产水电阻率可在40 min以后基本稳定在17 MΩ.cm以上。在此基础上提出了一种新型的非蒸馏法注射用水制备工艺即反渗透-二级电去离子-超滤(RO-2EDI-UF)工艺。研究表明,RO-2EDI-UF制备注射用水,在理论上是可行的;工程实例也证明,产水电导率、细菌内毒素等各项指标均达到中国药典对于注射用水的标准。此工艺可显著降低系统设备投资、降低能耗,减少污水排放和噪声污染,水利用率较高,所制的注射用水具适宜的温度。完全可以替代离子交换法和蒸馏法用于注射用水的制备。     

Continuous production of high-purity water by electro-deionisation

Operating conditions were investigated for a packed-bed membrane cell for electro-deionisation of brackish or tap water to give high-purity water with electrical conductivity of the order 0.1 μmho/cm. Flow rates of 10–40 h^?1, current densities of 0.5–5 mA/cm², and incoming solution concentrations of up to 0.01 N were used. It was shown that strongly acidic cation-exchange resin plus strongly basic anionexchange resin in volume ratio 1:1 was the most effective, and that particle size needed to be 60–80 mesh and resin bed thickness 3 mm for optimum current efficiency in purifying water to the required standard.     

Desalination costs in Australia: A survey of operating plants

A survey of desalination costs in Australia was conducted using data obtained from plant operators, and is reported in second quarter 1986 A$. Unit water costs range from $0.76/kL (for a precursor to deionisation for boiler feed) to $14/kL (for emergency supplies for an island resort).

However, an average figure for desalination of brackish water is $3–$4/kL, and for seawater, $5–10/kL in medium-sized installations.

Capital costs for brackish water plants have been correlated with plant design capacity ranging from 10 to 3400 kL/d.

There is insufficient information to allow a proper comparison between reverse osmosis and electrodialysis for brackish water desalination.     

Antifouling membrane based on sodium alginate coated polyamide thin film composite for desalination of brackish water

Sodium alginate coated polyamide thin film composite (SA/PA-TFC) membranes were synthesized for the desalination of brackish water through reverse osmosis. Membranes were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, AFM, thermogravimetry, and universal testing machine for structural analysis, crystallinity, morphological, compositional, thermal, and mechanical properties, respectively. The effect of feed pressure on water flux and % salt rejection was quantified. Simulation results generated using the commercial process simulator PRO/II were in good agreement with the experimental data. Case studies using simulator were performed for brackish water with different salinity to optimize operating pressure based on product unit cost (PUC) by varying the feed pressure and membrane area. The calculated PUCs were found to be 0.9 and 0.3 $/m³ for corresponding feed total dissolved solids (TDS) concentrations of 5000 and 500 mg/L at an optimum pressure of 10 bar, to achieve a salt rejection of 98% using a membrane area of 335 m². We believe these membranes are a prospective solution for brackish water desalination.     

Performance study of RO systems in Saudi Arabia

Desalination of water is one of the most important engineering tasks facing Saudi Arabia today. Lacking unlimited supplies of potable Water, the Kingdom must depend upon the desalination process of brackish well water or sea water to satisfy the ever increasing demands. These demands are expected to reach the 430 MGD figure in 1980 and 700 MGD in 1985.

Abstract

until quite recently, the reverse osmosis played a rather modest role in the country's desalination program and was almost exclusively limited to brackish water applications and plants not exceeding a capacity of 1 MGD. Within the last year, significant changes took place in favor of these processes. The estimated total output of RO units to be commissioned this year will be about 70 MGD. This figure includes the 3.2 MGD plant for desalting the sea water in Jeddah and the 55 MGD plant in Riyahd from brackish well water.

This paper deals primarily with the performance of RO systems, their cost of operation/maintenance and the factors affecting the cost. These factors may be divided into three groups as related to feed water, system design and system operation. The quality of feed water and good pretreatment plays an extremely important role in performance of a RO system. This study pays special attention to these parameters in expectation that more cost effectiveness will evolve in the future either through a better understanding of the processes or an improved process design match to materials employed.     

Entsalzung von Umkehrosmosekonzentraten mittels elektrisch getriebenen Membranverfahren zur Maximierung der Permeatausbeute einer Prozesswasseraufbereitungsanlage

Worldwide present water stress situations lead to the necessity to use alternative water sources like brackish water or wastewater. To enable this, new desalination technologies like electrically driven membrane processes have to be implemented. These technologies were used to desalinate the reverse osmosis concentrate of a process water treatment plant up to a certain point, at which the resulting diluate could be used as feed water for the reverse osmosis. As a result, the concentrate volume to be discharged was halved and the permeate yield of the overall plant was increased. A focus was set on the required energy consumption for the additional treatment step.     

Optimization of solar-powered reverse osmosis desalination pilot plant using response surface methodology

A solar thermal and photovoltaic-powered reverse osmosis (RO) desalination plant has been constructed and optimized for brackish water desalination. The central composite experimental design of orthogonal type and response surface methodology (RSM) have been used to develop predictive models for simulation and optimization of different responses such as the salt rejection coefficient, the specific permeate flux and the RO specific performance index that takes into consideration the salt rejection coefficient, the permeate flux, the energy consumption and the conversion factor. The considered input variables were the feed temperature, the feed flow-rate and the feed pressure. Analysis of variance (ANOVA) has been employed to test the significance of the RSM polynomial models. The optimum operating conditions have been determined using the step adjusting gradient method. An optimum RO specific performance index has been achieved experimentally under the obtained optimal conditions. The RO optimized plant guarantees a potable water production of 0.2 m³/day with energy consumption lower than 1.3 kWh/m³.     

Optimized design of a reverse osmosis system with a recycle

Small scale brackish water desalination units are used in remote areas and their sustenance depend on the twin factors of consistency of product water quality and availability of raw water resources. A mathematical model has been developed based on the input parameters of feed salinity, basic membrane characteristics, feed temperature, desired product quality and quantity to predict the operating recycle ratio at constant operating parameters. This ensures the consistent quality of product water at the same time minimizing the raw water consumption. The algorithm used include calculation of recovery, determination of membrane configuration and operating pressure within the guidelines of manufacturer's specified hydrodynamic parameters. The model has a range with respect to reference value of design. The model can estimate the feed quality variation +10% to −70% and feed temperature variation ±5EC based on the design reference value.     

The role of desalination in bridging the water gap in Jordan

The water resources of Jordan have always been scarce. The demand for water in the country exceeds the available resources and the gap between the water supply and demand is continuously increasing. Furthermore, the quality of water resources has dramatically deteriorated in recent years, which prevented the utilization of some resources. To secure the economic sustainability of the country, it is important at this stage to consider non-conventional water resources, such as sea and brackish water desalination. This study examines the water resources of Jordan, projected water demand, and the gap between the demand and supply based on two scenarios. The possibility of closing this gap by water desalination was investigated. Both sea and brackish water desalination were considered. The analysis revealed that seawater desalination process is economically infeasible for domestic water uses at this stage. This is attributed to that Jordan is not an oil producing country and the location of sea shoreline in Aqaba is on the Red Sea, away from the consumption centers. However, seawater desalination may be a viable option for tourist and industrial enterprises that will be established as a result of the new Law of Aqaba Free Zone. The most convenient and realistic option for Jordan in the short term, is the desalination of brackish water by reverse osmosis (RO). The brackish water with total dissolved solids between 2000-10000 mg/l is available from many aquifers and springs of the country. The study concluded that Jordan is facing a severe water crisis. Until recently, the water planners have not given the water desalination the required attention as a potential source of water supply. Taking into account the progress that is being achieved in the field of desalination technology, Jordan has to consider the desalination option more seriously and to start building a national capacity in the field of water desalination. It was emphasized that desalination is not a substitute to traditional water resources, it is rather a supplementary source that can contribute in bridging the water gap of the country.     

Simulation of a forward feed multiple effect desalination plant with vertical tube evaporators

In recent years, vertical tube falling film evaporators have been widely used in desalination industries. In this paper mathematical modeling of a multiple effect evaporators (MEE) system has been carried out for brackish water desalination. The system includes a set of forward feed vertical tube evaporators with thermal vapor compression (TVC) and a condenser. Modeling has led to calculation of several parameters such as overall heat transfer coefficients, entrainment ratio and recovery of the process which is restricted by scale formation. A scaling prediction chemical model has been employed to calculate the allowable rate of recovery for prevention of scale formation. Physical properties of streams have been assumed as functions of temperature and salinity. A code has been developed for simulation of the process based on mass and energy balance equations. Results showed maximum allowable recovery of 74% for the treated brackish water sample with total dissolved solid (TDS) of 14,761 ppm is achievable. Dealing with mentioned sample under specified set of conditions, it was concluded that changing the number of effects from 3 to 8, enhances gained output ratio (GOR) value from 3.8 to 7.5. However, specific heat transfer surface is increased from 215 to 1052.