5405503 Process for desalinating water while producing power

Hybrid membrane system for desalination and wastewater treatment : Integrating forward osmosis and low pressure reverse osmosis

Although current water desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. It is well-known that polymer hydrogel network has the ability to absorb water via swelling. In the case of polyelectrolyte hydrogels, the charges localized on the polymer chains, which mainly drive the swelling pressure inside the hydrogel, can also separate added salt via charge-based selectivity (Donnan exclusion). When combining this material with a temperature-sensitive polymer, the heat generated by solar energy can trigger the desorption process via conformational change of polymer chains. Hence, hydrogels designed from both materials, polyelectrolyte and thermo-responsive polymer can reduce the salinity of water, such as brackish water by means of reversible thermally-induced absorption and desorption desalination processes. In addition, the desorption process can also be achieved based solely on a polyelectrolyte hydrogel system by altering the ionization of charges within the hydrogel via pH. In this thesis, hydrogel-based water desalination process were developed using acrylic acid (AAc)/sodium acrylate (SA)-based polyelectrolytes as the charge-based separation function, alone or with a combination of N-isopropylacrylamide (NIPAAm) as thermo-responsive comonomer. In the latter case, a series of chemically cross-linked polymeric hydrogels were synthesized via either free radical-initiated copolymerization or reversible addition-fragmentation chain transfer (RAFT) polymerization, thus realizing different macromolecular architecture. According to the nature of hydrogels, the reversible sorption/desorption state were triggered by either chemical stimulus (pH), or physical stimulus (heat) as the thermo-responsive polymer introduced into the hydrogels. In detail, the effect of hydrogel composition as well as the influence of the macromolecular architecture on the swelling/deswelling behavior for the synthesized hydrogels were studied. For this, their properties including their responses to external stimuli were investigated, and their ability to desalinate brackish water as well as the effciency of such desalination process were evaluated. Generally, the results demonstrated correlations between macromolecular architecture of the network structure and their performance in the proposed desalination process, such as salt rejection and desalination capacity. Moreover, the potential of the best performance materials for applications was also discussed.

Thermal and membrane based desalination plants are being operated all over the world to address the demand of fresh water required by industries and large cities in water scarce coastal areas. The desalination and energy are very much interlinked, as plants are energy intensive. The energy consumption of desalination plants varies from 5 to 15 kWh m-3 of product water depending on the technology. In addition, the percentage of reject seawater/brine exiting the plants varies from 60% to 80% depending on the desalination technique. The concentrated reject brine is a source of valuable trace elements/metals, which is an untapped source that is wasted. With advances in Desalination technologies, it has been established that recovery of critical metals and elements and their selective recovery from reject brine of desalination plants gives an added advantage of energy credits to desalination plants as well as reduce cost of desalinated water [1, 2]. Research and technological developments are required for brine mining from desalination plants, i.e., by the recovery of nuclear fuel and other valuable materials (e.g. U, Li, Rb), from reject brine streams. This is being achieved by adsorption of these elements/ions onto a selective sorbent that is dipped either in reject brine/inlet seawater or in the open sea [1]. The major factor determining the practical utilization of the technology and lifetime of the adsorbent is fouling of the adsorbent by suspended particles or due to biological growth. The paper presents the status review on a recovery of important trace metals and other alkali metals from seawater and highlights the potential of Indian desalination plants for the recovery of trace metals. The adsorption studies carried out using radiation grafted polymeric adsorbents along with fouling studies are discussed in this paper. The studies involve determination fouling tendency of the adsorbents in a different environment, and recovery of uranium and vanadium from the reject brine. The paper also gives the schematic diagram and major unit operations involved in process flow scheme.

Water scarcity is an alarming global problem for a growing population with depleting sources of fresh water. Desalination is thus becoming an important solution for water management to address such looming shortage of the municipal water supply. At present, several technologies dominate the desalination industry which can be categorized either as a thermal process such as multi-stage flash distillation or a membrane process such as that of reverse osmosis. New desalination systems are also being developed to make the process more cost-effective and energy efficient. Hence, this work proposes a systematic approach for optimal selection of desalination systems using fuzzy analytic hierarchy process (FAHP) and grey relational analysis (GRA). Fuzzy AHP addresses the vagueness involve in the trade-off of the criteria or attributes used in evaluating the alternatives. On the other hand, the GRA solves the multiple criteria decision problem by aggregating the entire range of performance attribute values for every alternative into a single score in spite of incomplete information. An illustrative case study was presented wherein five desalination systems namely reverse osmosis (RO), combined reverse osmosis and forward osmosis (RO-FO), electrodialysis (ED), multi-stage flash distillation (MSF), and combined forward osmosis and membrane distillation (FO-MD) were evaluated. These desalination systems were compared to each other with respect to energy requirement, land footprint, system efficiency, economic viability, and maturity of technology. Sensitivity analysis was also done to determine the robustness of the modeling results from the variation of weights of the criteria.

The crystallization of salts is widely recognized as one of the most significant causes of damage to many cultural objects consisting of porous materials, such as monuments, sculptures, historic buildings, wall paintings, etc. A common response to salt damage problems are treatments aimed at reducing the salt content of the affected object, most typically through the application of poultices. Poultices are applied to porous materials in order to extract soluble salts. The process of poulticing is relatively simple in theory, but in practice the efficiency of the salt extraction is more difficult to predict. This study aims to develop a better understanding of the physical principles of the salt and moisture transport by which poultices function. A desalination treatment by poultice includes two main phases. The first is the wetting phase: water is transported from the poultice into the wall, where it starts to dissolve the salts. The second phase is the salt extraction. The dissolved salt ions travel in the form of an aqueous saline solution from the substrate into the poultice. This salt migration can be the result of two different processes. The first is generated by the existence of a concentration gradient between the substrate and the poultice. In this case the salt ions diffuse through the solution. The other one is realized by the capillary water flow from the substrate to the poultice (generally resulting from drying). In this case the salt ions are transported by the moving solution (advection). If salt ions are advected from the substrate into the poultice by capillary moisture flow, a concentration gradient will be established. Because of this salt concentration an osmotic pressure will develop. One of the aims of this study was to investigate the potential contribution of osmotic pressure to salt extraction during drying of the poultice. For this purpose we have conducted a series of experiments to investigate the influence of osmotic pressure on ion transport processes. Nuclear Magnetic Resonance (NMR) techniques were used to obtain information on the water and salt distribution in the poultice/substrate system during desalination. The results of the experiments show that the contribution of the osmotic pressure can have a significant influence on the desalination process. Poultices which contain different mixes of clay and sand were studied in order to understand the influence of each component on the drying behavior of the poultice. Desalination experiments in controlled environmental conditions were carried out on substrates with well known pore size distributions. NMR was used to obtain information on the water and salt distribution in the poultice/ substrate system during desalination. The study demonstrates the relation between salt extraction and pore structure parameters of the poultice/substrate system. It also shows the influence of some additional factors, such as an interventional layer between substrate and poultice, on the salt extraction during the desalination treatment.

Despite being a mature process, production of fresh water using desalination is still a challenge. Desalination is broadly divided into two categories; thermal desalination processes, such as multi-stage flash, and semi- permeable membrane process, such as Reverse Osmosis (RO). This work is aimed at developing correlations for water permeability coefficient (Kw) and salt permeability coefficient (Ks) as a function of feed salinity and pressure using experimental data for a continuous RO process. For three different feed salinities of 15, 25, and 35 g/L at two different pressures of 40 and 45 bara experimental values of Ks and kw values are taken from the literature. Planar and ellipsoidal least square methods are used to correlate kw and Ks as a function of feed salinity and pressure, which are then embedded within the continuous RO process model to evaluate the process performance in terms of maximising the recovery ratio while optimizing the area and pressure to get the desired freshwater salinity. gPROMS model builder is used to simulate and optimise the process.

Flaring of gas often having high heating value results in considerable economic and energy losses in addition to significant environmental impacts. Power generation through combined gas and steam turbine cycles may be considered as a suitable flare gas recovery process. Thermal sea-water desalination is a process that requires a considerable amount of heat; hence it may be used in downstream of power generation cycles. Energy is the largest section of the water generation cost of all desalination processes. The energy cost of thermal distillation sea-water plants is close to 50-60% of water generation costs. In the current study, the generation of power and desalinated water through the gas turbine cycle, steam cycle, and multistage flash (MSF) method using flare gas of cheshmeh khosh are investigated. The economic parameters related to the different scenarios considered for the production of power and water are evaluated in the current research. According to the economic evaluation carried out, the most economically profitable scenarios for the investigated co-generation plant is generating as much as possible power in the steam turbine and using the remaining heat in the low-pressure outlet steam in the MSF desalination process. The results show that by increasing steam turbine outlet pressure from 3 bar to 78 bar, power and water generation is changed from 697 to 581 MW and 1557 to 2109 m3/h, respectively. Also, by increasing the outlet pressure of the steam turbine from 3 to 78 bar, the total capital cost is changed from 1177 to 1192 MUSD, and the operating cost is changed from 117.85 to 117 MUSD/year. Finally, operating profit will decrease from 300 to 50 MUSD/year, and payback time will change from 3.92 to 4.75 years.

Removal and Recovery of Phosphonate Antiscalants

Nowadays, water and electricity are closely interdependent essential sources in human life that affect socio-economic growth and prosperity. In other words, electricity is a fundamental source to supply a seawater desalination process, while fresh water is used for cooling this power plant. Therefore, mutual vulnerability of water treatment and power generation systems is growing because of increased potable water and electricity demands especially during extremely-hot summer days. Hence, this paper presents a novel framework for optimal short-term scheduling of water-power nexus aiming to minimize total seawater desalination and electricity procurement cost while satisfying all operational constraints of conventional thermal power plants, co-producers and desalination units. Moreover, advanced adiabatic compressed air energy storage (CAES) with no need to fossil fuels can participate in energy procurement process by optimal charging during off-peak periods and discharging at peak load hours. A mixed integer non-linear programming (MINLP) problem is solved under general algebraic mathematical modeling system to minimize total water treatment cost of water only units and co-producers, total fuel cost of thermal power plants and co-generators. Ramp up and down rates, water and power generation capacities and balance criteria have been considered as optimization constraints. It is found that without co-optimization of desalination and power production plants, load-generation mismatch occurs in both water and energy networks. By incorporating CAES in water-power grids, total fuel cost of thermal units and co-producers reduce from $1222.3 and $24933.2 to $1174.8 and $24636.8, respectively. In other words, application of CAES results in $343.9 cost saving in benchmark water-power hybrid grid.

Conservative desalination technology including distillation requires high energy and cost to operate. Hence, pretreatment process can be done prior to desalination to overcome energy demand and cost reduction. The objective of this investigation is to study the effect of calcination temperature of hybrid catalyst in photocatalytic reactor system in the seawater desalination i.e salt removal in the seawater. The catalyst was synthesized via wet impregnation method with 1:1 weight ratio of TiO 2 and activated oil palm fiber ash (Ti:Ash). The catalyst was calcined at different temperature, i.e. 500 o C and 800 o C. The study was carried out in a one litre Borosilicate photoreactor equipped with mercury light of 365 nanometers for two hours with 400 rpm mixing and catalyst to seawater sample weight ratio of 1:400. The Chemical Oxygen Demand (COD), pH, dissolved oxygen (DO), turbidity and conductivity of the seawater were analyzed prior and after the testing. The fresh and spent catalysts were characterized via X-Ray Diffractogram (XRD and Nitrogen physisorption analysis. The calcination temperature significantly influenced the adsorption behaviour and photocatalytic activity. However, Ti:Ash which calcined at 800 o C has less photocatalytic activity. It might be because the surface of fiber ash was sintered after calcined at high temperature. The Ti:Ash catalyst that calcined at 500 o C was found to be the most effective catalyst in the desalination of seawater by reducing the salt concentration of more than 9 % compared to Ti:Ash calcined at 800 o C. It can be concluded that catalyst calcination at 500 °C has better character, performance and economically feasible catalyst for seawater desalination.

A novel multi-salt crystallization process is presented to separate the salts from the desalination brine and is optimized using the gradual optimization integration strategy based on T-H diagram. Firstly, the process is simulated by Aspen Plus software to obtain the cold and hot load curve and the bottlenecks and unreasonable heat transfer processes are analysed. Secondly, considering the energy utilization and conversion procedure, the turbine and/or heat pump are introduced to improve the process. Then the parameters of production process and utility system are adjusted. Thirdly, the new stream information is obtained by process simulation and the new composite curves are drawn, which will guide the further adjustment of the system. If the new composite curves do not satisfy the process demand, then the above steps are repeated. Through several improvements, two approximate parallel hot and cold stream curves are constructed. The hot streams and cold streams are maximum possible matched, and the amount of utility and power consumption is significantly reduced. In a case study, two optimization schemes are adopted: the feed brine is preheated by the flash steam and the heat pump crystallization technology is introduced. The results show that the energy consumption of two optimized processes is 94.8 kW and 90.1 kW, and the total energy loss decreased 86.7 % and 87.3 %.

This study discloses the role of graphene and bismuth chalcogenides in membranes designed to water desalination. Nanocomposite membranes were tailored and characterized from morphological and physicochemical point of views. Membrane distillation (MD) and membrane crystallization (MCr) experiments were implemented in order to evaluate how confined fillers can affect the final performance of membrane process in terms of flux, rejection, nucleation and growth rate of salts crystals. Chemisorption was envisaged as a crucial mechanism in assisting water diffusion and ion aggregation.This study provides new insightful indication about the powerful function of graphene and materials beyond graphene in membranes designed for scalable MD and MCr. Higher performances could make these membrane operations extremely challenging for future competitive water desalination processes.

Seawater or brackish water processing technology to freshwater was known as desalination. Process desalination of evaporation is one of the desalination technique, that effective and economics especially to a coastal area that have larger sun intensity than another. Therefore, in this research will discuss about designing house roof society in coastal region. Tub evaporative and basic tub plate planning size that made for 4,5m x 10m house of floordeck 600 coated with 5,4 cm concrete thick mess. Tub evaporative size is 3m × 10m × 0,02m. Collective freshwater channel are besides the tub with size 0,75m × 10m. The sketch of roof used easel that made of galvalume profile C 100mm × 50mm × 20mm × 4mm and gording is made of hollow 40mm × 40mm × 0,5mm. Outside cover roof is polytron polycarbonate with 4,2 mm thickness and inside roof fiberglass with 1 mm thickness. Freshwater volume can be produced by tub space 3m × 10m × 0,003m is 89,74 L by seven hours heating process on 485 W/m 2 sun intensity.

This thesis aims to develop eco-friendly biochar (BC)-based materials for water treatment. The BC-based materials can be controlled and enhanced their properties, e.g., physical, chemical, or/and electrochemical properties. The improvement of these properties can be beneficial for surface or interface-related or ionic transport processes, resulting in efficient water treatment. Firstly, the application of high-quality meso/micropore-controlled hierarchical porous carbon (HPC) was synthesized by a hard template method utilizing BC and then used to adsorb copper ions from an aqueous solution. The preparation procedure included two main steps: base leaching and physicochemical activation. During the activation process, porosity characteristics (i.e., specific surface area (SSA) and mesoporosity) were controlled by altering the KOH impregnation ratio, activation time, and temperature under the CO2 atmosphere. As evidenced, HPC material has a very high SSA of 2330 m2 g–1 with an 81% mesoporosity. Besides, a copper adsorption study was performed using the HPC samples with different pore structures and characteristics. The most obvious finding to emerge from this study was that a high adsorption capacity (265 mg g–1) and fast removal of copper ions can be obtained by HPCs synthesized from activated BC. The large SSA ensures a high adsorption capacity, while the mesopores are preferable for faster ion removal during the adsorption process. Secondly, HPC as an eco-friendly electrode material was fabricated from BC for electrosorption of ions. The porous structure in the HPC can be controlled by different activation times to optimize the material physicochemical and electrochemical properties. The HPC achieved a high SSA (1839 m2 g−1), large PV (1.21 cm3 g−1), and mesoporosity (58%). The HPC electrode exhibited excellent electrochemical properties with a high specific capacitance of 120.5 F g−1 at 5 mV s−1 in a 1 M NaCl solution as well as good reversibility for capacitive charge storage. The large ion-accessible SSA, interconnected pore structure among micropores and mesopores, and high mesoporosity of the HPC electrode played crucial roles in the enhancement of the electrosorption performance. The HPC electrode exhibited a high electrosorption capacity of 8.11 mg g−1 and a mean deionization rate of 0.92 mg g−1 min−1 for 20 mM NaCl in single-pass capacitive deionization. The associated charge efficiency and energy consumption were 48.1% and 0.064 kWh mol−1, respectively, indicating a low energy requirement of water desalination. Furthermore, the HPC electrode showed good regeneration ability in consecutive cycles for the removal of inorganic pollutants, i.e., NH4+, Mg2+, and Cu2+, with electrosorption capacities of 1.54, 1.53 and 0.52 mg g−1, respectively. Consequently, HPC from tailored activated rice husk BC can provide a new opportunity to achieve high-performance electrosorption in various water and wastewater treatment processes. As(III) species, accounting for a predominant proportion in groundwater, is more toxic, and difficult in adsorption than As(V) species. Thirdly, an active MnO2/rice husk BC composite (MBC) was successfully prepared to enhance the As(III) removal for groundwater remediation. MBC achieved an improved porosity structure (i.e., SSA, PV, and mesoporosity), providing abundant reaction or interaction sites for surface or interface-related processes such as redox transformation and adsorption of arsenic. As a result, the significant enhancement of the arsenic removal capacity can be achieved by using MBC. More specifically, MBC showed a great removal capacity of As(III), which was tenfold higher than that of BC. It can be ascribed to the redox transformation of As(III) via MnO2, resulting in more effectively adsorbed As(V) species. In addition, pH was an important factor, which influenced the As(III) removal capacity. Under the alkaline condition, the As(III) removal capacity of MBC was lower than that of under acidic and neutral conditions due to the negative effects of electrostatic repulsion. Importantly, a powerful transformation capability of As(III) via MBC was presented, namely, only 5.9% As(III) has remained in the solution under neutral condition. The As(III) adsorption was governed by surface complexation mechanisms of functional groups, i.e., COOH, OH, and Mn-OH. Most interestingly, the application of the MBC in the treatment of simulated groundwater demonstrated an efficient arsenic removal of 94.6% and the concentration of arsenic as low as the 10 µg L–1 WHO guideline. The results of this thesis provided strong evidence that BC-based materials can be efficiently applied in water treatment (e.g. heavy metal and ammonium removal, desalination, water softening, and redox transformation of As(III)). The applications of these BC-based materials demonstrated great flexibility through various treatment processes such as adsorption, electrosorption, and integrated process of transformation and adsorption.

An environmental impact assessment is an assessment of the possible positive or negative impact that a proposed project may have on the environment, together consisting of the natural, social and economic aspects. Environmental Impact Assessment (EIA) of Masjid-I-Sulaiman desalination and operating unit’s project in the southern of Iran using Rapid Impact Assessment Matrix (RIAM) method is presented. The field is located between 32° 06' 53.60'' North and 40° 10' 54.18'' East, in the Masjid-I-Sulaiman area. It is planned to produce rate of 55,000 oil barrels per day. In this study, an attempt was made to identify and assess the likely key impacts of desalination and operating units in two phases: Construction and Operation. In the evaluation process, positive and negative environmental impacts of Masjid-I-Sulaiman desalination and operating units were assessed based on the results of multi-disciplinary team approach and the field survey data using RIAM method. In this regard, given that in today’s world for a closer look at the environmental impact of development projects and achieve a safer reply, using new implementation methods such as MCDM can be appropriate. The results of assessment reveal that the percent volumetric positive effects in alternative 1is more than percent volumetric negative impact on the second alternative, therefore the implementation of the project with some mitigation plans and monitoring program for the alternative 1 was chosen as a best option is accepted. Then on the basis of current evaluation suggest monitoring program and mitigation plans.