Improving Recovery in Reverse Osmosis Desalination of Inland Brackish Groundwaters Via Electrodialysis PDF Download

Author: William Shane Walker
Publisher:
ISBN:
Category :
Languages : en
Pages : 374

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Book Description
As freshwater resources are limited and stressed, and as the cost of conventional drinking water treatment continues to increase, interest in the development of non-traditional water resources such as desalination and water reuse increases. Reverse osmosis (RO) is the predominant technology employed in inland brackish groundwater desalination in the United States, but the potential for membrane fouling and scaling generally limits the system recovery. The general hypothesis of this research is that electrodialysis (ED) technology can be employed to minimize the volume of concentrate waste from RO treatment of brackish water (BW) and thereby improve the environmental and economic feasibility of inland brackish water desalination. The objective of this research was to investigate the performance sensitivity and limitations of ED for treating BWRO concentrate waste through careful experimental and mathematical analysis of selected electrical, hydraulic, and chemical ED variables. Experimental evaluation was performed using a laboratory-scale batch-recycle ED system in which the effects of electrical, hydraulic, and chemical variations were observed. The ED stack voltage showed the greatest control over the rate of ionic separation, and the specific energy invested in the separation was approximately proportional to the applied voltage and equivalent concentration separated. An increase in the superficial velocity showed marginal improvements in the rate of separation by decreasing the thickness of the membrane diffusion boundary layers. A small decrease in the nominal recovery was observed because of water transport by osmosis and electroosmosis. Successive concentration of the concentrate by multiple ED stages demonstrated that the recovery of BWRO concentrate could significantly improve the overall recovery of inland BWRO systems. A mathematical model for the steady-state performance of an ED stack was developed to simulate the treatment of BWRO concentrates by accounting for variation of supersaturated multicomponent solution properties. A time-dependent model was developed that incorporated the steady-state ED model to simulate the batch-recycle experimentation. Comparison of the electrical losses revealed that the electrical resistance of the ion exchange membranes becomes more significant with increasing solution salinity. Also, a simple economic model demonstrated that ED could feasibly be employed, especially for zero-liquid discharge.

Author: Eric M.V. Hoek
Publisher: Springer Nature
ISBN: 3031795083
Category : Technology & Engineering
Languages : en
Pages : 194

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Book Description
Over the past half century, reverse osmosis (RO) has grown from a nascent niche technology into the most versatile and effective desalination and advanced water treatment technology available. However, there remain certain challenges for improving the cost-effectiveness and sustainability of RO desalination plants in various applications. In low-pressure RO applications, both capital (CAPEX) and operating (OPEX) costs are largely influenced by product water recovery, which is typically limited by mineral scale formation. In seawater applications, recovery tends to be limited by the salinity limits on brine discharge and cost is dominated by energy demand. The combination of water scarcity and sustainability imperatives, in many locations, is driving system designs towards minimal and zero liquid discharge (M/ZLD) for inland brackish water, municipal and industrial wastewaters, and even seawater desalination. Herein, we review the basic principles of RO processes, the state-of-the-art for RO membranes, modules and system designs as well as methods for concentrating and treating brines to achieve MLD/ZLD, resource recovery and renewable energy powered desalination systems. Throughout, we provide examples of installations employing conventional and some novel approaches towards high recovery RO in a range of applications from brackish groundwater desalination to oil and gas produced water treatment and seawater desalination.

Author: Masoume Jaberi
Publisher:
ISBN:
Category : Brackish waters
Languages : en
Pages : 240

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Book Description
The worsening global scarcity of freshwater threatens worldwide peace and prosperity, which are intimately tied to the availability of clean, fresh water (J. E. Miller, 2003). One approach for alleviating this threat is desalination, which can turn brackish and saline water sources into freshwater, and electrodialysis reversal (EDR) is a proven and widely used technology that can desalinate brackish waters in inland areas such as the southwestern United States. In a significant advantage over other membrane-based systems like reverse osmosis, EDR's ability to clean itself renders the system resistant to scaling and fouling and allows it to operate at high levels of water recovery. In a further benefit, this system typically requires less energy than thermal distillation to desalinate brackish water, leading to a reduction in overall desalination costs. To identify the operating limits of EDR and find the parameters that maximize its performance, this research investigated the performance sensitivity and limitations of EDR for treating brackish groundwater through careful experimental and statistical analyses of selected electrical, hydraulic, and chemical variables. Experimental evaluation was performed using a pilot-scale EDR system and natural feedwaters at the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM; statistical analyses were carried out using SAS software. Based on the experimental results and statistical analyses, multi-linear regression models were developed for EDR systems for removal ratio, current, and specific energy consumption.

Author: John Francis Thompson
Publisher:
ISBN:
Category :
Languages : en
Pages : 300

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Book Description
The treatment and desalination of inland water via reverse osmosis (RO) technology is gaining momentum for upgrading brackish groundwater and developing supplemental fresh water for various regions. In brackish RO plants, high water recovery is critical in order to minimize the volume of residual RO concentrate (brine), given the economic and environmental challenges of concentrate management. However, high recovery may be limited by mineral salt scaling resulting from supersaturation of sparingly soluble minerals (e.g., CaSO4, BaSO4, CaCO3, SiO2). Mineral scaling results in membrane surface blockage, reduction of permeate flux and shortening of membrane lifetime. In order to control or prevent mineral scaling, effective mitigation methods must be developed and tested (i.e., the relationship between RO operating conditions and mineral scaling). To accomplish the above, early detection of mineral scaling is essential. To meet the above challenges, a novel high-pressure RO membrane monitoring system was developed to allow direct membrane surface imaging. The membrane monitoring system (MMS) was interfaced with a slipstream from an RO plant, whereby captured membrane surface images were analyzed online. The present monitoring approach demonstrated, for the first time, early detection of silica scale formation and growth kinetics. Detailed silica scaling studies revealed that scaling consisted of discrete silica particles embedded in a silica "gel" layer. The membrane monitoring approach also served to evaluate the impact of a membrane biofilm on concentration polarization (CP) and mineral scaling kinetics. It was shown that biofilms enhanced CP within the biofilm and significantly exacerbated mineral scaling. The membrane monitoring approach was subsequently deployed in a field study of desalination of brackish agricultural drainage (AD) water. In these studies, the membrane monitor was integrated with a mobile RO pilot plant, developed at UCLA, for real-time field optimization of RO operating conditions for averting mineral scaling. The above approach demonstrated that effective feed filtration for removal of suspended particles is critical for mitigating mineral scaling and reducing nucleation triggered by surface deposited particles. Moreover, antiscalant selection and dosage optimization was feasible under field conditions which also enabled determination of the maximum feasible water recovery level.

Author: Committee on Advancing Desalination Technology
Publisher: National Academies Press
ISBN: 030913434X
Category : Science
Languages : en
Pages : 312

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Book Description
There has been an exponential increase in desalination capacity both globally and nationally since 1960, fueled in part by growing concern for local water scarcity and made possible to a great extent by a major federal investment for desalination research and development. Traditional sources of supply are increasingly expensive, unavailable, or controversial, but desalination technology offers the potential to substantially reduce water scarcity by converting the almost inexhaustible supply of seawater and the apparently vast quantities of brackish groundwater into new sources of freshwater. Desalination assesses the state of the art in relevant desalination technologies, and factors such as cost and implementation challenges. It also describes reasonable long-term goals for advancing desalination technology, posits recommendations for action and research, estimates the funding necessary to support the proposed research agenda, and identifies appropriate roles for governmental and nongovernmental entities.

Author: Khaled Elsaid
Publisher:
ISBN:
Category : Brackish waters
Languages : en
Pages : 173

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Book Description
Groundwater is considered the major source of domestic water supply in many countries worldwide. In the absence of surface water supplies, the use of groundwater for domestic, agricultural, and even for industrial purposes becomes essential, especially in rural communities. Groundwater supplies typically are of good quality, and the quality is reasonably uniform throughout the year compared to that of surface water, thus making it suitable for direct use, or simple to treat. A disadvantage of groundwater is the content of dissolved salt as many have a moderate-to-high salinity. The high salinity makes water brackish and thus it requires desalination before use. This has led to wide use of groundwater desalination to produce good-quality water in many regions around the world. Nevertheless, a problem of desalination processes is the generation of a concentrate stream, sometimes called brine or reject, which must be properly managed. The management of brine from brackish groundwater desalination is a significant issue if located far from the coast (i.e. inland plants) or far from public channel to discharge such brine. Some options for brine disposal from inland desalination plants are evaporation ponds, deep-well injection, disposal to municipal sewers, and irrigation of plants tolerant to high salinities. Each of these disposal methods may result in many environmental problems such as groundwater contamination, the decline in crop yields from agricultural lands, the formation of eyesores, decreasing the efficiency of biological wastewater treatment, and making treated sewage effluent unsuitable for irrigation. As a result, the brine management from inland desalination of brackish groundwater is very critical, and the need for affordable and environmentally benign inland desalination has become crucial in many regions worldwide. This work aims to develop an efficient and environmentally benign process for inland desalination of brackish groundwater, which approaches zero liquid discharge (ZLD), maximizing the water produced and minimizing the volume of concentrate effluent. The technical approach involves utilization of two-stage reverse osmosis (RO) units with the intermediate chemical treatment of brine stream that is designed to remove most of the scale-forming constituents, which foul membrane surface in RO and limits its water recovery and hence enable further recovery of water in the secondary RO unit. The treatment process proposed in this work is based on advanced lime softening processes, which have the ability to effectively remove scale-forming constituents, in addition to heavy metals and natural organic matters that might be present in the brine. The process has been applied to the brine produced from 1st stage RO i.e. primary brine stream, to minimize the volume of the stream to be treated chemically, which in turn reduces the capacity of the treatment equipment. Analysis of groundwater quality and scale-forming constituents that are present in the brine stream upon desalination of groundwater has been performed. The analysis has revealed that in most cases of brackish groundwater desalination the recovery is limited by scaling due to calcium sulfate i.e. gypsum, and amorphous silica. Thus, the main objective set for the chemical treatment of the brine stream focused on removal of calcium, sulfate, and silica. Advanced lime softening based on high lime doses along with sodium aluminate, as in ultra-high lime with alumina UHLA process, has been proposed for chemical treatment of brine. Bench-scale experiments conducted to evaluate the effectiveness of the proposed chemical treatment for removal of scale-forming constituents, particularly calcium, sulfate, and silica by studying the different factors affecting the removals efficiency from synthetic solutions containing sulfate-only, silica-only, and model brine solution. The results obtained have revealed that the proposed process was very effective and results generally in high and quick removals of calcium, sulfate, and silica of more than 80% within 2 hrs under different experimental conditions. In addition, beneficial uses of different solid byproducts formed are investigated, by analyzing the solids resulted to qualitatively and quantitatively to identify the different solids present. This offers the potential to lower both costs and solid disposal problems of solids formed being considered as added value product rather than solid waste that has to be properly managed. Results have shown that the solid precipitate contains a wide range of solids that generally composed of calcium, magnesium, aluminum along with carbonate, sulfate, and silicate, which have several potential applications as soil sub-grade, and in cement industry. Equilibrium model to simulate the chemical treatment process that is able to predict the required chemical reagents doses, effluent water quality for a given influent water quality and treatment levels has been developed utilizing OLI stream analyzer, the developed model was found to well predict the performance of the chemical treatment at equilibrium conditions. Rigorous membrane separation model has developed in Aspen Custom Modeler to more accurately model RO desalination, which is to be combined with the developed equilibrium model to formulate a complete 1st Stage RO-Chemical Treatment-2nd Stage RO process model. The developed complete and validated model has been then used to fully and accurately simulate the performance of the proposed Zero Liquid Discharge desalination process. The present work results in three novel achievements: first, introducing a very effective intermediate chemical treatment, which efficiently remove sulfate, particularly from brine. Most of the previously proposed intermediate treatment processes remove sulfate as calcium sulfate i.e. gypsum, however in the introduced process, sulfate is removed in calcium-aluminum-sulfate complexes, which has very low solubility, making the brine highly undersaturated with respect to gypsum, and hence lowering the fouling propensity in the secondary RO, leading to maximizing the overall recovery. In addition, the chemical treatment has been successfully modeled for better simulate of its performance for different brine qualities, which are usually encountered in brackish ground desalination due to the high location-specific nature of groundwater quality. Second, the developed membrane model has treated the species present in water as ions, accounting for monovalent and divalent ions separately, and obtaining a different permeability coefficient for their transport through the membrane. This is different from most developed RO models, which simplify the transport through the membranes to only water and salt permeability coefficients. This treatment results in better and more refined modeling and simulation of the RO membrane separation, as the RO membrane interact differently to ions present in water. Third, the complete process model, results from combining the developed equilibrium model of the chemical treatment, and membrane separation model, has revealed very promising results of achieving high recovery desalination of about 93.5% suitable for drinking water purposes, which is higher by about 90% than most of the reported literature, whose result in reducing the brine volume from 25% in conventional desalination to only 6.5% in the proposed process, i.e. brine volume reduction of 74% relative to conventional inland desalination, and 35% relative to other high recovery processes, at reasonable chemical treatment levels.

Author: Mark M. Benjamin
Publisher: John Wiley & Sons
ISBN: 1118632273
Category : Technology & Engineering
Languages : en
Pages : 906

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Book Description
Explains the fundamental theory and mathematics of water and wastewater treatment processes By carefully explaining both the underlying theory and the underlying mathematics, this text enables readers to fully grasp the fundamentals of physical and chemical treatment processes for water and wastewater. Throughout the book, the authors use detailed examples to illustrate real-world challenges and their solutions, including step-by-step mathematical calculations. Each chapter ends with a set of problems that enable readers to put their knowledge into practice by developing and analyzing complex processes for the removal of soluble and particulate materials in order to ensure the safety of our water supplies. Designed to give readers a deep understanding of how water treatment processes actually work, Water Quality Engineering explores: Application of mass balances in continuous flow systems, enabling readers to understand and predict changes in water quality Processes for removing soluble contaminants from water, including treatment of municipal and industrial wastes Processes for removing particulate materials from water Membrane processes to remove both soluble and particulate materials Following the discussion of mass balances in continuous flow systems in the first part of the book, the authors explain and analyze water treatment processes in subsequent chapters by setting forth the relevant mass balance for the process, reactor geometry, and flow pattern under consideration. With its many examples and problem sets, Water Quality Engineering is recommended as a textbook for graduate courses in physical and chemical treatment processes for water and wastewater. By drawing together the most recent research findings and industry practices, this text is also recommended for professional environmental engineers in search of a contemporary perspective on water and wastewater treatment processes.

Author: Brian Carey McCool
Publisher:
ISBN:
Category :
Languages : en
Pages : 208

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Book Description
Various regions around the world are confronted with dwindling water supplies and thus the need for exploiting non-traditional inland brackish water resource, as well as reclamation and reuse of municipal wastewater and agricultural drainage (AD) water. Reverse osmosis (RO) membrane desalination is the primary technology for inland brackish water desalting. However, successful implementation of RO technology requires operation at high product water recovery (>85%) in order to minimize the volume of generated concentrate (i.e., brine). Brine management is a key factor governing the economics of inland water desalination. Therefore, brine volume reduction is critical to enabling various brine residual management options. At high water recovery, dissolved mineral salts (e.g., CaSO4, BaSO4, CaCO3) may become concentrated above their solubility limits and may crystallize in the bulk and onto the surface of the RO membranes. Mineral crystallization leads to membrane scaling and hence leads to flux decline, increased process costs, and shortening of membrane life. Therefore, the attainable desalination water recovery is limited by mineral scaling. Many inland brackish water sources contain high concentrations of sparingly soluble mineral salts. In certain areas, such as in California's San Joaquin Valley (SJV), brackish water is near saturation with respect to calcium sulfate and barium sulfate. Based on the current work, single-stage RO desalination in SJV would generally be limited to ~50-70%. In order to desalt brackish water of high mineral scaling propensity at a high recovery level (>85%), the feasibility of intermediate concentrate demineralization (ICD) of primary RO (PRO) concentrate, as a means of enabling secondary RO (SRO) desalting, was investigated with a focus on brackish water having high concentrations of gypsum salt precursor ions (i.e., calcium and sulfate). Accordingly, a two-step chemically-enhanced seeded precipitation (CESP) ICD process was developed in which the PRO concentrate is treated prior to further SRO desalting. The first step is lime precipitation softening (PS) which serves to induce sufficient CaCO3 crystallization in order to remove residual antiscalant (AS), a PRO feed treatment additive (generally polymeric) used for scale control, that would otherwise inhibit precipitation (in the ICD) of the target mineral salt scalants. Subsequently, gypsum seeded precipitation (GSP) is carried out to reduce the level of calcium sulfate saturation. The CESP process was evaluated experimentally, in a batch crystallizer, using synthetic PRO concentrate and also PRO concentrate generated in the field, from AD water, using a spiral-wound RO pilot plant. The effect of residual AS (from the PRO stage) on retardation of mineral salt precipitation (in the ICD) was evaluated using both a generic (polyacrylic acid) and a commercial AS. Laboratory batch CESP studies were carried out in which the CESP process conditions were first optimized with respect to the required lime and gypsum seed doses. For raw brackish water that was about 98% saturated with respect to gypsum, PRO desalination at 52%-62% recovery yielded a brine stream 70-150% above saturation. CESP treatment, at lime doses of 0.25-0.35 mg/L and gypsum seeding of 4-5 g/L, enabled reduction of gypsum concentration to only 10-15% above its saturation. In general, the sequential processes of lime treatment for 10-20 minutes followed by ~1 hr of GSP were sufficient to achieve the above level of gypsum desupersaturation. GSP alone reduced gypsum saturation by only ~5%. PRO brine desupersaturation via CESP was feasible due to the effectiveness of AS removal (up to 90% for AS content of up to 10 mg/L in the PRO brine). Analysis of AS removal using a fundamental AS adsorption model, along with measurements of the size distribution of precipitating CaCO3 crystals, indicated that the area for AS adsorption provided by lime-induced nucleation of CaCO3 crystals is the key factor governing AS removal. In order to establish the feasibility of deploying CESP as a continuous process, a numerical model was developed for a fluidized bed reactor for the GSP stage. Model simulations indicated that the required level of calcium sulfate desupersaturation could be maintained by solids recycling leading to a steady-state particle size distribution. Process simulations and economic analysis were carried out for the integrated process of PRO, CESP and SRO (PRO-CESP-SRO) demonstrating the existence of an optimal recovery (with respect to product water treatment cost). For the evaluated SJV brackish AD water source, the optimal recovery was about 93%. Overall brackish water treatment cost, when considering the disposal cost of high salinity AD water, was lower for PRO-CESP-SRO relative to a similar process based on conventional PS or utilizing a single stage RO which would be of limited recovery (

Author: Noe Ortega-Corral
Publisher:
ISBN:
Category : Atomic force microscopy
Languages : en
Pages :

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Author: Sahil R. Shah
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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In countries such as India, where continuous access to treated piped-water is uncommon, many have resorted to desalinating brackish groundwater to meet their drinking needs. This form of decentralized treatment is performed at the community-scale, as is common in rural areas, and within individual homes, using point-of-use (POU) purifiers. This thesis develops methods to lower the costs and improve the efficiencies of two technologies for these applications: electrodialysis (ED) and reverse osmosis (RO). Batch ED desalination, which relies on recirculating water to reach a desired product concentration, is often conducted at constant voltage. This operation scheme causes the membrane area to be underutilized because the ratio of applied current to limiting current is initially low during the batch cycle. By applying a time-varying voltage to the ED stack, we raised this ratio and increased production rate by up to 37% using the same membrane area. In parallel, we derived an analytical prediction of the batch time and validated it under varying feed and product concentrations, and flow velocities. The experiments and model together suggest that the proposed control scheme will improve production rate most significantly when desalinating through large concentration changes at low flow velocities. This work will assist engineers and operators seeking to size, evaluate, and maximize the production performance of new and existing batch ED systems. Decreasing the energy requirements of community-scale RO, by recovering hydraulic power from the brine stream, will make off-grid deployments more affordable. However, existing energy recovery devices (ERDs) are prohibitively expensive. We investigated the feasibility of leveraging ubiquitous gear and sliding vane positive-displacement mechanisms within a fixed-recovery architecture to provide a low-cost ERD solution. By modeling the coupled behavior of the pump, ERD, and RO train, we showed that production performance is sensitive to volumetric efficiency. Based on this finding, vanes were selected over gears for prototyping. The prototype enabled a 17% decrease in measured power consumption, and through characterizing friction, we determined that these savings could be doubled by balancing pressure loads on the vane mechanism's rotor. This work lays the groundwork for realizing an affordable ERD for community-scale RO treatment. Finally, today's POU RO purifiers only recover 20-30% of the input feed as drinking water and consume significant energy. By testing and analyzing a POU RO system, it was identified that recirculating the brine within a semi-batch configuration could help address these limitations. We engineered such a system using off-the-shelf parts, and in initial testing, showed that it could achieve recoveries of up to 75% without affecting production rate and quality. With further testing and refinement, this semi-batch system could make POU water desalination more efficient.