An electrodialysis sea water desalination system powered by photovoltaic cells

An electrodialysis sea water desalination system powered by photovoltaic (PV) cells is beeing developed. In this sort of system, the most important subject is a way to apply the varying electric power from the PV cells directry to electrodialysis with a small capacity lead battery. We use a partially desalinated water (PDW) storage system for this. When a large electric output from the PV cells is obtained, sea water is desalinated to partially desalinated water (PDW:salinity of which is between sea water and fresh water) and when a small output is obtained, the desalination from PDW to fresh water is completed. In this system, as varying outputs from the PV cells are used directly in electrodialysis, the capacity of the lead battery is reduced, and an economical system is realized. A demonstration plant (capacity:10m³/day) was constructed for this system, and has been operating since June, 1986.     

Energy-saving electro dialyzer for sea water desalination

Tokuyama Soda Co. ltd. has developed an energy-saving skid mounted electrodialyzer for sea water desalination. This equipment is suitable for making fresh water for drinking and industrial use. To desalinate 25°C sea water and turn out one ton of product water. This equipment consumes only 8.5 KWH of electricity and 0.09 Kg of concentrated sulfuric acid. Low energy consumption is achieved by adoption of low electric resistance membranes, new spacer and new designed one pass type system. Low running cost, easy maintenance and low initial installment cost place the equipment good position in the desalination field. And also we applied high temperature electrodialysis up to 50°C of sea water and get figure 6.0 KWH for one ton of product water.     

Desalination in the gaza strip: drinking water supply and environmental impact

More than 90% of the population of the Gaza Strip depends on desalinated water for drinking purposes. About 90% of the groundwater is unacceptable for drinking as a result of contamination by nitrate and chloride. One of the major options for resolving the water problems is the utilization of desalination technology for both sea and brackish water. The objective of this article is to address desalination water management in its embryonic stage in the Gaza Strip. The sources of drinking water supply, distribution system and the environmental impact of brine water will be fingered in detail. Desalination facilities range from large seawater plants to small brackish desalination units on a home scale. Governmental, non-governmental and private desalination plants are common. The distribution system of desalinated water is a responsibility of governmental, non-governmental, private small community bodies and even individuals. Disposal of brine water is made either directly or indirectly into the sea, sewage system, poor land, channels, wadies, etc. Brine constituents have an adverse impacton the surrounding environment, e.g., sea life, soil, wastewater treatment plants and the groundwateraquifer. The lack of real environmental impact assessments, especially for mid- and home-scale units may lead to a deterioration of the environment. The fragmentation of the responsibilities of water desalination, distribution of desalinated water and the disposal of brine water suggest that urgent action should be taken (e.g., legislation or establishment of a supervisory body). In other words, strict policies and management actions are to be taken in order to alleviate the health and environmental impact of an important and uncontrolled new system.     

The water problem in egypt

Egypt faces the prospect of rapid growth of populatlon which is a vital problem since agricultural land is not available at the same rate. More land should be reclaimed through development of water resources.The Nile river constitutes an immense water supply but one third of its water is lost through pumping low salinity drainage water to the Mediterranean Sea utilizing costly electric power. Therefore, feasibility studies on recycling this water must be carried out.Along the banks of the Nile, drinking water could be obtained supplied through either small water purification plants or electrodialysis desalination plants, and the economics of the two methods should be compared before deciding on either method.Another source is underground water with a salinity varying between 2000 and 11,000 ppm. For such brackish water, either the electrodialysis or reverse osmosis process can be used.Then there is the Egyptian sea shore which extends over 3000 km. and where the salinity of the sea varies between 33,000 and 45,000 ppm. Here flash distillation processes are suitable.The present paper briefly describes available water resources in Egypt and discusses possible solutions to supplying the fresh water required in different areas.The present investigation concentrates on the feasibility and economics of utilizing the electric supply from the grid at periods other than the peak loads for operating electrodialysis plants. It is estimated that a series of electrodialysis plantsrunning for lOh/day would provide 2.6 million m³/day at an operating cost of 10¢/m³ in addition to capital costs.     

Editorial

The first seawater desalination plant by electrodialysis in the world started its operation in September, 1974 at Noshima island of Hofu city, Yamaguchi Prefecture, Japan. The capacity of the plant is 120 m³/day and the plant has been supplying fresh water from the sea for the 800 inhabitants of the island. Batchwise operation is utilized to simplify the process because of its relatively small capacity, but the operation is fully automatic to supply fresh water continuously using a storage of proper capacity. The water cost is relatively high but lower than that of conventional distillation processes of the same capacity.     

Removal of hardness in fermentation broth by electrodialysis

Lysine fermentation broth was desalinated by electrodialysis to reduce hardness concentrations as a pretreatment procedure for the purification and recovery of amino acids. Electrodialysis performance was investigated in terms of the rate of reduction in conductivity in dilute solutions and electrodialysis cell resistance for different ion exchange membranes at a constant current density. Among the membranes investigated in this study, membranes with high water content showed the better performance for hardness removal. Fouling experiments revealed that organics gave rise to fouling effects on the anion exchange membrane during demineralization of the lysine fermentation broth. The pulsed electric field with the half‐wave power enhanced the electrodialysis performances by mitigating membrane fouling in desalination of the lysine fermentation broth. This study successfully demonstrated the potential use of pulse power as an effective cleaning‐in‐place (CIP) method during electrodialysis of fermentation broth. © 2002 Society of Chemical Industry     

除盐水系统建模与物料衡算分析

新鲜水的工业除盐系统通常涉及膜分离（例如超滤、反渗透等），阴阳离子交换树脂床和储罐等。其中离子交换和膜分离单元可看作单入口双出口的半连续过程单元，具有间歇用水过程的特征。然而，尚未有关于除盐水系统的间歇水网络综合的研究报告。对除盐水系统中双出口半连续单元和水箱分别建立流量衡算、杂质质量衡算模型和储罐模型。根据不同工况下除盐水的需求量，利用GAMS软件平台对建立的数学模型进行求解，得出除盐水系统中每个储罐的容量和对应的新鲜水用量。进一步根据储罐最大容量需求，设计出满足不同工况条件下储罐容量。简化的工业案例研究验证了所提出模型的有效性。     

等电流电渗析模型脱盐试验

等电流操作电渗析比等电压操作电渗析更容易通过调整膜对数控制多段电渗析各段的脱盐率和极化点。通过不同方案试验对比，提出了合理的等电流操作电渗析的膜对数组合。通过试验验证了Ca(HCO2)2型井水在预处理中加酸酸化，再进行电渗析脱盐工艺比预处理中未加酸酸化工艺脱盐效果较明显。     

The SDAWES project: an ambitious R&D prototype for wind-powered desalination

This paper describes the design and operational strategies of an ambitious prototype for a desalination system powered exclusively by wind energy. The system, installed on the island of Gran Canaria, was designed with several objectives in mind: (a) to determine experimentally the feasibility of the stand-alone operation of wind farms isolated from the conventional power grids and supplying energy for a number of desalination techniques (reverse osmosis, electrodialysis reversal and vacuum vaporcompression; (b) to verify the operational feasibility of the various desalination techniques when the energy source driving the system is an intermittent one; and (c) to analyze the influence that a variety of operational strategies have on the volume and quality of the desalinated water produced and on the useful working life of the main components of the desalination plants. The first of these three questions has been resolved with the feasibility of such stand-alone systems now clearly demonstrated. As for the second question, initial tests would seem so far to indicate that the reverse osmosis technique is the most suitable for use in stand-alone wind-powered desalination systems. The results that are still to come from the remaining studies will be of vital importance for regions like the Canary Islands, which suffer from a scarcity of potable water, lack conventional energy sources, but do have at their disposal wind energy resources.     

Limestone selection criteria for EDR water remineralization

Water scarcity in Mediterranean regions has led to projects that increase water resources by desalination. In this context, it is planned to expand and improve the drinking water treatment plant of the Llobregat River near Barcelona (Catalonia, NE Spain), building the largest electrodialysis reversal (EDR) plant in the world. Llobregat River water shows high salinity due to the occurrence and exploitation of several geological formations upstream with minerals having high contents of Na, K, Cl, and Br. EDR desalinated water is highly reactive and shows a low degree of mineralization. In consequence, remineralization is necessary to equilibrate the water in order to avoid aggressiveness and corrosion in pipelines and to re-introduce some essential ions for human health. Running outlet water through limestone (CaCO₃) is a simple and cheap process for remineralization. Five commercially available limestones were characterized (mineralogical and chemical composition, BET surface area, SEM analysis) and compared experimentally at both laboratory and pilot-plant scales during the EDR remineralization process. The main criteria in selecting a limestone for EDR water remineralization are its compositional purity in terms of both mineralogy and chemistry, and its textural characteristics. Texture mainly influences the suspended particulate matter (PM) generation, i.e., consumption and system performance. To minimize the negative effects of these features, an assessment, using SEM analysis and batch tests contacting limestones and desalinated water, of the capacity of PM generation is recommended.     

A small solar desalination plant for the production of drinking water in remote arid areas of southern Algeria

The common methods of desalination salt water for production of fresh water by distillation, reverse osmosis and electrodialysis are intensive energy techniques. However, in remote arid areas, the desalination needs not exceed a few cubic meters per day. This decentralised demand favours local water production by developing other desalination processes, especially those using renewable or recovered energy (solar, geothermal, etc.). Solar desalination process is one of these methods used to resolve the scarcity of fresh water. Several reviews have been published by different authors. Small production systems as solar stills can be used if fresh water demand is low and the land is available at low cost. To supply the population of remote arid lands of South Algeria with drinkable water, solar distillation of brackish waters is recommended. It satisfies some of theses demands. Solar stills are used to produce fresh water from brackish water by directly utilising sunshine. These stills represent the best technical solution to supply remote villages or settlements in South Algeria with fresh water without depending on high-tech and skills. The production capacity indicates a possible daily production of far more than 15 l/m²d. Therefore, the still has a place in the upper range of known comparable products with regards to production output. This depends on the material used and the price of the solar stills and their accessories. The best working temperature solves most problems. Small, modular high-performance stills with features like the possibility of decentralised use, less maintenance and robust construction can help to reduce fresh water scarcity. The recent development of stills based on new concepts and heat recovery has been successful. The technical optimization is still in process today, it aims to improvement of the efficiency of these distillers. In our research work, a plant for brackish water distillation by directly sunshine and heat recovery was constructed and investigated experimentally and theoretically in South Algeria. This study aims the improvement of the performance of this solar distillation plant, conducted under the actual insulation, for brackish underground geothermal water desalination.     

The Libyan experimental on the environmental impact assessment for desalination plants

The desalination industries are considered to have a major role in developing human life. Recently this technology became widely distributed, and its construction along the coastal area has been widely reported. Many countries are adopting these technologies for securing the fresh water supply for consumer consumption all over the world. This situation has raised the need for researches to evaluate the environmental impact assessment (EIA) of these technologies on coastal line environment.

This study has been directed to monitor sea water quality used for feeding desalination plants to determine the concentrates of selected pollutants such as heavy metals by using chemical monitoring system to know their effects on the desalination units and other components. This study was conducted in the year 2003 from January to June. Samples were collected from feed water intake of Benghazi North desalination plant and Tobrouk desalination plant, both plants were chosen because of their importance for supplying fresh water for potable water and industrial uses.

The results of this study showed monthly differences in most tested parameters, these differences lead to the scale and corrosion by precipitation on the components of the desalination unites. The objectives of this study is to know the main reasons which caused increasing these concentrates in the sea water (study area) and know how to deal with.     

Studies on a single-stage solar desalination system for domestic applications

In this paper, an attempt has been made to study a single stage solar desalination system to get a daily yield of 10 1 of potable water. The experimental system consists of a flat plate collector, an evaporator, a single stage vacuum pump and a condenser. The input parameters such as solar irradiance and vacuum pressure in the flash evaporator are varied to find its influence on the performance output viz., system efficiency and yield per day. Efficiency of this plant is found to vary from 15% to 26% for the variation in beam solar radiation from 400 W/m² to 900 W/m². A maximum distillate yield of 8.5 1/d is obtained with collector area of 2 m². The frequency of operation of the vacuum pump and the yield of desalinated water for various beam solar radiations is carried out from which the cost of water is determined. The cost of desalinated water is found to be 0.9 e/l. The desalinated water is tested for various parameters and the results indicate that the quality of water is satisfactory and well below the permissible limits.     

利用可再生能源的反渗透膜法海水淡化方案探讨

该文对常规膜法海水淡化系统的系统功能、设备出力、蓄水能力、设备选型、运行管理等方面提出了优化调整意见,使之在安全运行的前提下,适应可再生能源电力波动的特点,如此不但能解决可再生能源发电量不稳定、发电量与用电负荷不匹配等问题,大幅提高可再生能源发电设备的利用小时数,还能解决我国淡水资源紧缺问题,创造利用可再生能源和海水资源的新循环经济模式。     

新型闭式太阳能海水淡化装置及其性能模拟

本文提出了一种闭式海水淡化装置,阐述了系统的工作原理,建立了相应的数学模型。就冷却水流量、海水喷淋量、集热器面积、蒸发器尺寸等因素对系统淡水产量的影响情况进行了计算机模拟,根据实验测得的气象数据对一天内系统淡水产量随时间变化情况进行了模拟,并根据典型的月平均日气象数据对系统一年内每个月的系统性能进行了分析。分析表明,不计系统夜间运行时的淡水产量,在西安地区系统淡水产量可以达到4.6kg/d.m2。     

1,3-丙二醇发酵液电渗析脱盐工艺的优化

研究了1,3-丙二醇发酵液电渗析脱盐过程中某些工艺参数,例如不同交联度离子交换膜的选择、不同碱离子发酵液以及原料液预处理方式等工艺对脱盐过程的影响。同时在前期实验的基础上,研究了淡浓室流速比、淡室流速和浓室初始浓度三因素对电渗析脱盐操作过程的影响,并利用正交试验对脱盐过程的工艺优化作了进一步的探讨。     

Solar power/desalination,pv*ed system

Photovoltaic/Electrodialysis, PV*ED, power/desalination system is studied in which the seawater feed is heated in the PV-cells. By varying feed concentration and temperature of the PV*ED system, it is shown in this paper that one could control the ratio of power to water production within a large range so that various demands for power and water could be met.     

Electrodialysis desalination designed for off-grid wind energy

An electrodialysis desalination plant has been set up and tested to treat brackish water while driven from an off grid wind energy system. The tests were carried out in the framework of a wider scope project, located on Gran Canaria Island (Spain). The main goal of this project was to test and identify the most suitable desalination systems for connection to the above-mentioned medium-scale off grid wind farm. After having previously analysed the behaviour of the system on-grid, the following stage was to develop an operational envelope for the electrodialysis reversal (EDR) unit while operating off grid, i.e., only coupled to the wind farm. The unit included power converters for the membrane stacks (DC-drivers) and variable frequency drivers (VFD) for the feed pumps. The tests were carried out to establish the power intervals for the EDR unit depending on the product flow rate specified as well as water quality. Product flow rate between 3 and 8.5 m³/h, power requirements between 4 and 19 kW, while product water conductivity ranged between 200 and 500 μS/cm were recorded. The desalination unit showed good flexibility, adapting smoothly to variations in wind power, even when sudden drops or rises occurred. The control system, slightly modified from a standard design, can cope with such sudden variations. Good agreement between performance predicted with software and the actual operating performance was observed. The presence of harmonics in the electric system due to DC drivers and VFD became harmful for the control and electric system, and care must be taken through appropriate mitigating measures.     

Comparison of classical solar chimney power system and combined solar chimney system for power generation and seawater desalination

An alternative method of heat and moisture extraction from seawater under the collector of a solar chimney system for power generation and seawater desalination is investigated with the aim of estimating the output of power and fresh water when used in seawater desalination using one-dimensional compressible flow model. It is found that the temperature and velocity of the airflow inside the chimney in the combined plant is less than that inside the chimney in the classic plant due to the release of vapor latent heat as the air rises up the chimney. Additionally, the power output from air turbine generators and water generators in the combined plant is less than that of the classic plant. Furthermore, a revenue analysis based on the price of fresh water and electric power in Dalian, China shows that the chimney less than 445 m high for the proposed combined solar chimney power plant having a collector 3000 m in radius is more economical than for the classic plant. The critical chimney height is found to depend on the local price of fresh water and electricity.