电渗析苦咸水淡化技术研究进展

电渗析苦咸水淡化技术具有脱盐效果好、成本较低、绿色环保等优点,但存在制膜工艺繁琐、传质模型不够精确、能效有待提升等问题。本文首先分析了苦咸水电渗析用离子交换膜的制备及改性方法,对膜材料存在的问题进行了探讨。综述对比了苦咸水电渗析在简化模型、理论模型、半经验模型方面的原理及最新进展,系统总结了常规苦咸水电渗析过程的运行方式和工艺优化策略,并进一步介绍了以新型电去离子、冲击电渗析、可再生能源驱动电渗析为代表的新型电渗析过程在苦咸水淡化方面的原理及应用。在此基础上,提出了今后的研究方向集中于降低制膜成本、优化传质模型、探究集成膜法淡化工艺以及新型电渗析过程等方面。     

Optimal design of an electrodialysis brackish water desalination plant

This paper considers the optimal design and operation of electrodialysis (ED) desalination plants. In general an ED plant aims to produce potable water from a high salinity source, like brackish water or high salinity water. The system is modelled mathematically as mixed-integer non-linear programming (MINLP) optimization problem, determining the number of desalination stages, the membrane area, the total required energy so as to minimise the total annualised cost of the investment accounting for both infrastructure and operating costs. Two examples from the literature illustrate the applicability of the proposed approach and evaluate the quality of the results obtained.     

RO membrane autopsy of Zarzis brackish water desalination plant

Tunisia, located in a semi-arid zone, has limited water resources. The shortage of good water quality in particular at the south regions required a brackish water desalination to supply these regions with potable water. Zarzis desalination plant, working since 1999, has revealed difficulties related to the loss of membrane performances. In the aim to determine the reason of membrane fouling, foulant layer were analysed. The membrane autopsy has achieved by different methods, such as TOC (total organic carbon) measurement, SEM (scanning electron microscopy), AFM (atomic force microscopy), FTIR (fourier transform infrared spectroscopy) analysis, diffraction by X-ray. Results show that the foulant layer composed mostly of SiO₂, clay, organic matter (polysaccharide, protein), CaSiO₃, Fe₃O₄, AlPO₄, and CaSO₄. The characteristics bonds obtained by IR indicate the presence of polysaccharides and proteins that constitute a source for further microbiological growth; this is the problem of biofouling. The metallic elements results of corroded stainless steel and internal coating of cartridges filter that are damaged by the silica particle rejected by sand filters. The scale of CaSO₄ and CaSiO₃ deposition is owing to the bad antiscaling efficiency. The results are presented and discussed in the light of new trends in material.     

Reverse osmosis in the desalination of brackish water and sea water

To make RO an economical process, plant and operating costs have been reduced by developing compact modules, led by polyamide hollow fibre modules which recover energy from the reject when desalinating highly saline brackish water and seawater. Such plants only start to pay their way at product rates of around 400m³ /d +. Energy costs for desalination systems with lower capacities can also be reduced considerably by operating the RO plants at conversion rates of more than 30%. To what extent the required higher conversion rates can be obtained for a particular application depends on concentration of scales-forming content matter (calcium sulphate, strontium sulphate, barium sulphate and calcium carbonate), salt content of the raw water, concentration of fouling substances such as iron, manganese, anorganic and organic matter, risk of biological growth due to algae, shells and bacteria. The scope and type of conditioning and pre-treatment are based on these factors.     

Characteristics of RO foulants in a brackish water desalination plant

This study identified the membrane fouling of a two-stage RO process of the Bai-sha brackish water desalination plant facing serious fouling problems. Two membrane modules, one from each stage, were autopsied and diagnosed for the cause for the failure of the RO system. Different morphologies were exhibited on the fouled membrane. Results suggested that the fouling on the first-stage membrane tended to be organic and biological, while that on the second-stage membrane appeared to be scaling. Higher than 85% of the foulants on the first stage membrane were organic substances in opposed to the 5 to 8% of those on the second stage membrane. However, the total organic matter on the second stage membrane was more than that on the first stage one. The thick layer of scalants on the surface of the second-stage membrane was identified to be calcium carbonate of which the crystal was clearly seen in the SEM images. The scaling was thickest at the outlet of the membrane. Huge amount of microbes were found on both membranes. The FTIR results also suggested the existence of extracellular polymeric substance (EPS) on the first stage membrane. This study recommended that the recovery rate, pH and the potential for bio-fouling should be defined at the real operation.     

Wind turbine-inclined still collector integration with solar still for brackish water desalination

This paper presents a new hybrid desalination system that constitutes of wind turbine (WT) and inclined solar water distillation (ISWD) integrated with main solar still (MSS). The new developed system is designed, fabricated and evaluated under actual environmental conditions. A small wind turbine is used to operate a rotating shaft fitted in the MSS to break boundary layer of the basin water surface. Also, an ISWD system which consists of an inclined flat solar absorber plate covered with black-wick medium is attached to the exit of MSS. The system can produce distilled and hot water. The heating and evaporating processes take place in MSS as well as ISWD, and then the water are condensing on the glass covers. The system was tested at different water depths (0.01, 0.02 and 0.03 m), different water flow rates (25.0, 41.7 and 58.3 ml/min) and two modes of operation as due south and tracking the sun. Variation of ambient conditions, and water temperatures and outputs were used to evaluate each parameter. It was found that, increasing water depths at the same flow rate caused a decrease in the distilled water productivity. The amount of fresh water per square meter from the ISWD could be higher than the MSS with a range of 26.55 to 29.17% when the system is due south, while it ranged from 27.1 to 32.93% when the system is tracking the sun. The average daily efficiency of MSS and ISWD ranged from 67.21 to 69.59 and 57.77 to 62.01% when the system was due south, while it ranged from 66.81 to 69.01 and 57.08 to 62.38% when the system was tracking the sun, respectively. The water product cost is found to be 0.662 and 0.552 RMB/l (1 US $ = 7.43 RMB) when the system was due south and tracking the sun, respectively. The electricity annual savings is found to be 195.22 RMB/kWh/m². The distilled water quality as well as hot remaining water is good enough for domestic usage.     

Novel chitosan-piperazine composite nanofiltration membranes for the desalination of brackish water and seawater

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.     

Feasibility of reverse osmosis desalination of brackish agricultural drainage water in the San Joaquin Valley

The technical feasibility of reverse osmosis (RO) desalination of agricultural drainage (AD) water in California's San Joaquin Valley (SJV) was evaluated based on systematic analysis of water quality monitoring data and field water desalting tests in a laboratory plate-and-frame RO (PFRO) system. Thermodynamic solubility analysis and diagnostic PFRO desalting tests served to determine the feasible range of water recovery limits and to assess the mineral scaling potential. Analysis of the recovery limits imposed by scaling due to sparingly soluble salts (e.g. calcite, gypsum, silica) suggested feasible recoveries in the range of 46%-69%. Diagnostic PFRO desalting tests with five representative field water sources from the SJV (having gypsum and calcite saturation indices in the range of 0.12-1.03 and 2.9-9.5, respectively) confirmed the above recovery range. Mineral scale coverage was consistent with the observed flux decline. Deployment of RO technology for treatment of brackish SJV AD water would require site-specific process optimization given the geographic and temporal water quality variabilities. Therefore, RO operation with variable feed water quality (with respect to salinity and scaling propensity) and at sufficiently high recovery would require effective plant control, enabled by real-time mineral scale detection and adaptable process operation to mitigate mineral scaling.     

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.     

Modeling and simulation of the processes in desalination fuel cell fed with actual wetland brackish water

Journal of Applied Electrochemistry - Microbial desalination cell (MDC) is a new sustainable technique for simultaneous desalination, bioelectrochemical treatment, and power generation. In this...     

浅除盐水处理技术的应用

从小氮肥厂的应用人手,介绍了浅除盐水处理技术特点.结果表明,该技术在工业锅炉上推广应用,具有安全、经济的效果.     

Flocculation,precipitation, sedimentation and flotation for use as pretreatment stages for brackish water and seawater in desalination plants

The increased application of ion exchange and membrane processes for producing drinking water from qualitatively poor sources of raw water necessitates the use of advanced mechanical and chemical technologies as well as combinations of these. Our immediate objectives are as follows: (a) Use of precipitation and flocculation reactions for removing inorganic and organic matter; (b) separation of the suspension by using flotation and sedimentation; (c) application of these processes in compact units to minimize investment costs, and (d) inclusion of sludge treatment in water processing using mechanical techniques of dehydration.     

Metabolic effects of drinking brackish water

Brackish water in the Arava Rift Valley in Southern Israel has a high sulphate and magnesium content. The inhabitants who drink this water have hypocalcaemia and hyperphosphataemia suggestive of parathyroid hypofunction. They also have a low urinary pH, massive urinary sulphate excretion, and a compensated metabolic acidosis. It is suggested that the low urinary pH may be one of the reasons for the high incidence of uric nephrolithiasis in the region.     

Desalination of brackish water by electrodialysis

The performance of an electrodialysis unit comprising interpolymer type cation and anion-exchange membranes developed in this institute in single-stage and two-stage operation for desalting of brackish waters having different total dissolved solids has been studied highlighting the energy requirement and pressure drop under different conditions. For higher salinity waters, a two-stage reduction is advantageous with lower power requirements and power index. The results will be useful for design and installation of ED plants in brackish water sectors.     

Wind-Aided Intensified eVaporation (WAIV) and Membrane Crystallizer (MCr) integrated brackish water desalination process: Advantages and drawbacks

Due to the increasing of water shortage problems, the need for inland brackish water RO will continue to increase in future. However, the primary limitations to further application of RO inland are the cost and technical feasibility of concentrate disposal. In this work, Membrane Crystallizer (MCr) and Wind-Aided Intensified eVaporation (WAIV) technologies have been applied in order to mitigate the impact of concentrates on the environment. In particular, the research activity has been carried out on a desalination system in which brackish water was first pre-treated, then desalinated through reverse osmosis (RO) operation. Finally, RO concentrates were further treated in WAIV and MCr units. The effect of the presence of organic contaminants and antiscalants were studied by analysing RO operations working at different recovery factors and with different pre-treatments. In the absence of an antiscalant, RO operates at 75% recovery factor and at a pH low enough to ensure no calcium carbonate precipitation. In the presence of an antiscalant, RO process might work until a recovery factor of 88%. The analysed integrated RO + WAIV + MCr system allowed to reach recovery factors as high as 76.6–88.9% and limit brine discharge to less than 0.75–0.27% of the raw water fed to the system.     

Thin-film composite forward osmosis membrane prepared from polyvinyl chloride/cellulose carbamate substrate and its potential application in brackish water desalination

Synthesized by the reaction between α-cellulose and m-tolyl isocyanate (MTI), cellulose carbamate (CC) was blended with polyvinyl chloride (PVC) to fabricate substrates for thin-film composite (TFC) forward osmosis (FO) membranes. The introduction of CC into substrates improved both membrane structure and performance. The substrates exhibited higher porosity and hydrophilicity, and better connective pore structure; while rejection layer exhibited better morphology but limited cross-linked degree decrease after the introduction of CC. According to the results, the CC blend ratio of 10% was the optimal ratio. With this blend ratio, the TFC-10 membrane presented favorable water permeability (1.86 LMH/bar) and structure parameter (337 μm), which resulted in excellent FO performance (water flux with a value of 40.40 LMH and specific salt flux with a value of 0.099 g/L under rejection layer faces draw solution [DS] mode when 1 M NaCl and deionized water were utilized as DS and feed solution). In addition, the TFC-10 membrane showed good water flux and low-sulfate ion leakage in the potential application of brackish water desalination.     

脱盐水系统问题初探

化肥厂脱盐水装置自建成投产后一直存在着质量、产量、成本等重大问题，生产被动。在对脱盐水系统存在的问题进行了分析后，进行了相应的技术改造，从而降低了生产成本，改善了水质，保障了化肥装置的稳产高产。     

Assessing the sustainability of non-renewable brackish groundwater in feeding an RO desalination plant in Bahrain

The Rus-Umm Er Radhuma aquifer in Bahrain is a non-renewable source of brackish water (8-15 g/L), which forms a lens underlain everywhere with brines of over 100 g/L. Aquifer utilization has started in 1984 to feed a reverse osmosis (RO) desalination plant, with an economic life of 25 years (2010). Future plant upgrade strategy is formulated around boosting the plant production, which will require increasing the we llfield abstraction, in addition to a possible future rehabilitation program to extend the plant life by another 15 years (2025). The limiting factor in expanding the RO plant and its rehabilitation is the future feed water salinity, which have to be assessed before any investments are made to expand the RO plant and commission additional abstraction wells and implement the rehabilitation program. The aquifer management is based on mining a one-time brackish water reserve stored in the aquifer, the main management objective is stated as to sustain the aquifer future availability in feeding the desalination plant with a specified salinity limit of 20 g/L over the economic life of the plant of 25 years (1985-2010), and also over the plant extension period by rehabilitation (2010-2025). The stochastic analysis methodology utilizing conditional simulation is applied to conduct a risk assessment of violating these two pre-specified sustainability constraints under the proposed abstraction increase; and provided a tool to aid the decision-making process in the development and management of the aquifer under large uncertainties. Simulation results indicated that the risk of having the salinity of the wellfi eld produced water to increase due to the proposed increase in the wellfield abstraction to reach 20 g/L over the economic life of the plant (2010) is very small and minimal. However, it is questionable that the feed water salinity will be maintained under the proposed rehabilitation program to extend the plant economic life by another 15 years (2011-2025). For this option, it is recommended that model post-auditing be performed, and new updated predictions should be made as more data of potentiometry. salinity. and hydraulic parameters become available.     

Teaching water desalination through active learning

Active learning refers to the direct involvement of students in the learning process rather than being passive receptors of materials. This paper evaluates the implementation of active learning in teaching seawater desalination as an elective course in chemical engineering curriculum. Desalination is a multi-disciplinary engineering science that encompasses elements of water chemistry, material science, transport phenomena, thermodynamics, engineering design, and corrosion. Water desalination is an important course in most chemical and mechanical engineering curricula, where the design and analysis of different water desalination processes are addressed. The current teaching method, however, relies heavily on classical lecture-presentation of the course materials, without any direct involvement of the students. A simple approach that utilizes Excel and Ez-Solve in designing and analyzing desalination processes has been developed. Active learning is the central part of this course development, where students are heavily involved in class activities and can directly assess the effect of input variables on the design parameters, allowing them to carry out “What If” or parameter sensitivity analysis.