Reasons for the Fast Growing Seawater Desalination Capacity in Algeria

Seawater/brackish water desalination has been widely adopted by the Algerian Government in the last few years to supply potable water to municipality for various purposes mainly for domestic and industrial uses especially in areas where demand is high due to shortage of fresh water resources, rapid population growth and development of industry and tourism. Ten years ago, desalination was confined to the industrial use only especially in oil and gas industry as the country was relying on rain water and other available sources to supply fresh water to municipalities. Due to chronic drought conditions, the Ministry of Water Resources reviewed the national water strategy and a strong option for desalination was adopted where an ambitious program was thus put into action. Sixteen mega-plants, with capacities ranging from 100,000 to 500,000 m³ per day, primarily based on Reverse Osmosis technology, were launched in the last few years making the Algerian desalination program one of the world’s fastest growing markets. Five desalination plants, including the Africa’s largest seawater reverse osmosis project with a total capacity of 200,000 m³ per day, are already in operation and the remaining projects are either under construction or in commissioning. An integrated water resources management was also adopted as additional option to cuter the increasing water demand as there is also a great potential for water reuse and conventional water treatment. An additional benefit of this would be reducing the volume of treated wastewater disposed into the environment.     

Evaluation of the purification capacity of nine portable, small-scale water purification devices.

A test was performed to evaluate the microbial and chemical purification capacity of nine portable, small-scale water purification filter devices with production capacity less than 100 L/h. The devices were tested for simultaneous removal capacity of bacteria (cultured Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae and Enterobacter cloacae), enteric protozoans (formalin-stored Cryptosporidium parvum oocysts), viral markers (F-RNA bacteriophages) and microcystins produced by toxic cyanobacterial cultures. In general, the devices tested were able to remove bacterial contaminants by 3.6-6.9 log10 units from raw water. Those devices based only on filtration through pores 0.2-0.4 microm or larger failed in viral and chemical purification. Only one device, based on reverse osmosis, was capable of removing F-RNA phages at concentrations under the detection limit and microcystins by 2.5 log10. The present study emphasised the need for evaluation tests of water purification devices from the public safety and HACCP (Hazard Analysis and Critical Control Point) points of view. Simultaneous testing for various pathogenic/indicator microbes and microcystins was shown to be a useful and practical way to obtain essential data on actual purification capacity of commercial small-scale drinking-water filters.     

Responding to water challenges in Greece through desalination: energy considerations

Abstract

Desalination technology, and reverse osmosis in particular, is used by several island authorities in Greece to address water scarcity. However, this is a highly energy-intensive technique, requiring the consumption of significant quantities of fossil fuels. The case of Syros Island is presented, to demonstrate the strong water–energy link in the operation of desalination plants. The article also discusses the use of renewable energy sources as a means for reducing the energy intensity of desalination.     

望亭发电厂反渗透系统运行维护及管理

对望亭发电厂反渗透系统在实际运行中遇到的多介质过滤器出水浊度偏高、反渗透进水与浓水端压差较高、脱盐率降低等问题进行了分析。通过采取改变加药点、调整活性炭床运行和反洗工况、改接低压水冲洗管等措施解决了上述问题，以提高反渗透系统运行的安全性和经济性。     

北京水资源战略——三位一体的海水淡化生态技术

通过对输水成本、供水安全的分析,指出"南水北调"工程未必是从根本上解决北京水资源短缺问题的最佳战略选择。根据生态经济学原理,提出将海水淡化、风力发电、盐业化工三种行业有机结合,集成一种三位一体的生态经济技术。这种战略构想目的在于贯彻全球普遍倡导的可持续经济发展战略以及落实我国目前实施的"循环经济"政策,从而一劳永逸地解决北京水资源的短缺问题。清洁的风电为反渗透海水淡化提供动力需要,反渗透产物不仅仅产生淡水,同时又为海盐等化工生产创造了浓缩液条件,集成这3种行业可以形成一种污染物零排放的可持续清洁生产技术。     

反渗透处理高盐化工废水的试验研究

以经过两级混凝-超滤预处理后的化工废水为研究对象,通过试验考察了反渗透脱盐工艺处理高盐废水的效果和工艺稳定性。通过反渗透脱盐率和膜通量的变化来判定运行条件和进水水质对膜性能的影响。结果表明:系统稳定运行后对COD、电导率的平均去除率分别为94.38%、98.20%。在恒定压力(0.85 MPa)下,当进水TDS为3 500 mg/L时,膜性能稳定,膜通量衰减速率为0.008 6 L/(m2.h),在进水TDS>4 500 mg/L时脱盐率与膜通量随进水浓度的增大急剧下降。阻垢剂投加量为3.0~4.0 mg/L时,系统稳定运行150 h内压差稳定在0.04~0.07 MPa,出水满足该厂部分工艺用水的水质标准。     

公共建筑与住宅建筑非传统水源利用技术分析

对在公共建筑与住宅建筑中利用非传统水源的技术进行了比较和分析,着重研究了雨水、中水和海水利用技术,指出了各项技术的优缺点和适用条件。结果表明,采用雨水利用技术时,可以因地制宜采用与直接利用、渗透、调节等功能相关的技术组合;采用中水回用技术时,可采用有发展前景的膜生物反应器技术,也可采用生物接触氧化或混凝沉淀等技术;采用海水利用技术时,可根据各种技术特点选用多级闪蒸、低温多效、反渗透等技术,另外,用清洁能源淡化海水是海水淡化技术的发展方向。实践中选用非传统水源利用技术时,应综合各种因素,进行全面比较。     

膜法水处理技术在农村饮水安全中的应用研究

膜法水处理技术已经成为西部缺水地区进行苦咸水淡化、解决生活饮用水的主要方法之一。本文讨论了在农村饮用水处理中的几种膜工艺流程,分析了农村饮水处理中8套反渗透或纳滤膜苦咸水淡化系统的工艺参数。结果表明膜法淡化高含盐量苦咸水,出水水质均可达到或优于国家生活饮用水卫生标准,可以解决缺水地区的生活饮用水问题。     

Correlations between silt density index,turbidity and oxidation-reduction potential parameters in seawater reverse osmosis desalination

The reverse osmosis method is one of the most widely used methods of seawater desalination at present.Hydrophilic and desalting membranes in reverse osmosis systems are highly susceptible to the input pollutants.Various contaminants,including suspended organic and inorganic matter,result in membrane fouling and membrane degradation.Fundamental parameters such as the turbidity,the amount of chlorine injection,and silt density index(SDI)are the most predominant parameters of fouling control in the membranes.In this study,the operation system included a water intake unit,a pretreatment system,and an RO system.The pretreatment system encompassed a clarifier,a gravity sand filter,pressurized sand filters,and a cartridge filter.The correlation between the amount of chlorine injection in terms of the oxidation-reduction potential(ORP)and the SDI value of the input water was investigated at a specified site next to the Persian Gulf.The results showed that,at certain intervals of inlet turbidity,injection of a certain amount of chlorine into the raw water has a distinct effect on the decrease of SDI.     

Pressure retarded osmosis for energy production: membrane materials and operating conditions

Pressure retarded osmosis (PRO) is a novel membrane process to produce energy. PRO has the potential to convert the osmotic pressure difference between fresh water (i.e. river water) and seawater to electricity. Moreover, it can recover energy from highly concentrated brine in seawater desalination. Nevertheless, relatively little research has been undertaken for fundamental understanding of the PRO process. In this study, the characteristics of the PRO process were examined using a proof-of-concept device. Forward osmosis (FO), reverse osmosis (RO), and nanofiltration (NF) membranes were compared in terms of flux rate and concentration polarization ratio. The results indicated that the theoretical energy production by PRO depends on the membrane type as well as operating conditions (i.e. back pressure). The FO membrane had the highest energy efficiency while the NF membrane had the lowest efficiency. However, the energy production rate was low due to high internal concentration polarization (ICP) in the PRO membrane. This finding suggests that the control of the ICP is essential for practical application of PRO for energy production.     

Raising the reliability of water conditioning systems at the Sakhalin State Regional Power Plant

Results of a study of the water conditioning unit of the Sakhalin SRPP are presented. Analysis of the operating, regulating, and design documentation and of computations of the flow diagram has shown that a number of measures should be taken for stabilizing the water chemistry of the boilers and producing steam with parameters meeting the scheduled requirements. Variants of updating the WCU are considered, which are expected to raise the reliability of the system of water conditioning due to the use of membrane reverse osmosis plants in the water desalination system. __________ Translated from élektricheskie Stantsii, No. 1, January 2006, pp. 17–21.     

Recovery of calcium carbonate from waste gypsum and utilization for remediation of acid mine drainage from coal mines

The recovery of calcium carbonate from waste gypsum (a waste product of the reverse osmosis (RO) desalination process) was tested using sodium carbonate. Batch recovery of calcium carbonate from waste gypsum slurries by reacting with sodium carbonate under ambient conditions was used to assess the technical feasibility of CaCO(3) recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effect of key process parameters, such as the slurry concentration (%) and the molar ratio of sodium carbonate to gypsum were considered. It was observed that batch waste gypsum conversion significantly increased with decrease in the slurry concentration or increase in the molar ratio of sodium carbonate to gypsum. The CaCO(3) recovered from the bench-scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with commercial laboratory grade CaCO(3).     

Optimization of Osmotic Desalination Plants for Water Supply Networks

Water scarcity and the poor quality of water resources are leading to a wider diffusion of desalination plants using the Reverse Osmosis (RO) process. Unfortunately, the cost of a cubic meter of fresh water produced by an RO plants is still high and many efforts are in progress to increase the efficiency of the membranes used in osmotic plants and to limit the energy required by the process. A further reduction of the energy cost could be obtained by an optimal operation of the desalination plant so reducing the hourly energy cost, or by coupling the RO plant with an energy production plant based on direct osmosis (Pressure Retarded Osmosis PRO).The economic viability of the desalination process has been analyzed until now without accounting for the integration of the RO plant with the existing water network. This analysis is developed in the present paper with reference to a hypothetical change of water supply in a real network, where a desalination plant is used to satisfy the fresh water demand. Several scenarios will be analyzed to assess the minimum cost of fresh water production and water supply to the network, including the use of energy recovery systems, such as an integrated use of RO and PRO processes, or the regulation of pressure at the network intake by a micro hydro power plant.     

Energy and Water in Arid Developing Countries: Saudi Arabia,a Case-study

In Saudi Arabia, where water resources are limited, the availability of energy resources, including petroleum, natural gas and electricity, helped in solving the challenge of satisfying rapid and substantial increases in water demand for drinking and industrial and agricultural purposes. Thirty-five major dual-purpose multi-stage flash distillation (MSF) and reverse osmosis (RO) desalination plants were constructed on the Red Sea and Gulf coast to produce drinking water. The process energy requirements for MSF and RO range between 19.5 and 38 kWh/m3, and 0.5 and 9 kWh/m3, respectively. The MSF plants produce about 20% of the total national electricity production. About 85 000 wells were drilled to satisfy the increasing irrigation water demands. The energy requirements to pump 1 m3 from wells range between 0.4 and 0.8 kWh. The adoption of advanced technologies is continuing to reduce power consumption and water demand to conserve energy and water, and to minimize negative impacts on the environment.     

Desalination of Seawater using Geothermal Energy to Meet Future Fresh Water Demand of Saudi Arabia

The future economy of the Middle East countries (GDP growth) depends on the availability of fresh water for domestic and agricultural sectors. Saudi Arabia, for example, consumes 275 L/day per capita of water that is generated from desalination process using 134 x 10⁶ kWh of electricity. With 6 % population growth rate, demand for fresh water from fossil fuel based desalination plants will grow at an alarming rate. It has been reported that Saudi Arabia’s reliance on fossil fuels to generate electricity and generate fresh water through desalination using the same energy source is economically and politically unsustainable. This may lead to destabilisation of the global economy. However, Saudi Arabia has large geothermal resources along the Red Sea coast that can be developed to generate power and support the generation of fresh water through desalination. The cost of fresh water can be further lowered from the current US$ 0.03/m³. Among the gulf countries, Saudi Arabia can become the leader in controlling CO₂ emissions and mitigating the impact on climate change and agricultural production. This will enable the country to meet the growing demand of food and energy for the future population for several decades and to reduce food imports.     

On-site evaluation of the removal of 100 micro-pollutants through advanced wastewater treatment processes for reuse applications

The next challenge of wastewater treatment is to reliably remove micro-pollutants at the microgram per litre range in order to meet reuse applications and contribute to reach the good status of the water bodies. A hundred priority and relevant emerging substances were measured to evaluate at full-scale the removal efficiencies of seven advanced treatment lines (one membrane bioreactor process and six tertiary treatment lines) that were designed for reuse applications. To reliably compare the processes, specific procedures for micro-pollutants were applied for sampling, analysis and calculation of removal efficiencies. The membrane bioreactor process allowed to upgrade the removal efficiencies of about 20% of the substances measured, especially those that were partially degraded during conventional processes. Conventional tertiary processes like high rate clarification, sand filtration and polishing pond achieved significant removal for some micro-pollutants, especially for adsorbable substances. Advanced tertiary processes, like ozonation, activated carbon and reverse osmosis were all very efficient to complete the removal of polar pesticides and pharmaceuticals; metals and less polar substances were better retained by reverse osmosis.     

Analysis of the Water Resources Status in Kuwait

The acute lack of natural water resources in Kuwait is indisputable. The country essentially has one limited natural water resource that is groundwater, while the majority of the country's demands are met by seawater desalination. Notwithstanding this scarcity calls for careful foresighted utilization of the water resources, no clear plans is being followed. Attempting to initiate the planning process, this paper gives an assessment of the current status of water resources availability, production, future demand and expected increases in production, in Kuwait. While the desalination and wastewater reuse are only bounded by economical considerations, considerable efforts have already been made in assessing the baseline of the groundwater resources in Kuwait; nonetheless, no estimation is available of the aquifer system potential for sustainable development or even mining. The total water budget in 2001 is estimated at 655 Million m³, with desalination, groundwater production, and wastewater reuse constituting 59%, 32% and 9% respectively. The projected water demand for 2010 is 1020 Million m³. The plans of the Ministry of Electricity and Water and the Ministry of Public Works indicated that groundwater would cover 52% of the planned additional production, while desalination and wastewater reuse would cover 44% and 4% respectively. While the proposed increase in groundwater production would inevitably consume the only natural water resource of the country, only 40% of the generated wastewater is to be utilized. The absence of integrated planning is also manifested in the total planned production that surpasses the projected demands by more than 17%.     

Economic Analysis of Environmental Issues Regarding Seawater Desalination

Abstract

Desalination of seawater is becoming an important source of drinking water in many cities and towns, where the demand for water continues to increase, while the supply of fresh water is limited. We examine the economic aspects of several environmental issues that arise during consideration of desalination projects. We present a conceptual framework that demonstrates the differences between public and private objectives, and we use that framework to describe policies that can encourage firms and consumers to consider environmental impacts. Public policies can be implemented also to stimulate technological developments that will reduce the environmental impacts of desalination. We also examine the potential growth inducement effects of seawater desalination by describing the likely impacts of desalination on both the demand and supply components of the market for municipal water in a coastal area.     

舟山大中型海岛海水淡化技术研究

通过对海水淡化技术在舟山海岛地区的适用性分析,得出海水淡化是解决舟山大中型海岛缺水问题的有效途径的结论。然后以舟山本岛为范例,研究舟山市大中型海岛海水淡化的整个工艺流程,探讨了大规模取水工艺、大型海水前处理工艺、淡化处理装置、海水净化后处理和利用问题,为舟山市其他大中型海岛实施海水利用起到示范作用。     

Evaluation of electrochemically generated ozone for the disinfection of water and wastewater.

Effective wastewater treatment is critical to public health and well-being. This is especially true in developing countries, where disinfection of wastewater is frequently inadequate. People who live in these areas may benefit from wastewater disinfection using ozone. This study evaluated the ability of a new electrochemical process of ozone generation, which produced ozone continuously at high pressure and concentration by the electrolysis of water, to disinfect tap water and secondarily treated wastewater. Inactivation of Klebsiella terrigena, Escherichia coli, MS2 bacteriophage and poliovirus 1 was evaluated first in reverse osmosis (RO) treated water. Inactivation of K. terrigena (6-log), E. coli (6-log), MS2 (6-log) and poliovirus 1 (>3-log) was observed after 1 min of ozonation in a 1 L batch reactor. Experiments were then performed to assess the microbiological impact of disinfection using ozone on secondarily treated municipal wastewater. The effect of ozonation on wastewater was determined for total and faecal coliforms, bacteriophages and heterotrophic plate count (HPC) bacteria. Electrochemical ozone generators provided an effective, rapid and low-cost method of wastewater disinfection. Based on the results of this research, electrochemically generated ozone would be well suited to remote, small-scale, disinfection operations and may provide a feasible means of wastewater disinfection in developing countries.