جستجوی مقالات مرتبط با کلیدواژه « نمک زدایی » در نشریات گروه « مهندسی آب »

Saltwater desalination technologies have evolved as an effective and reliable solution for water supply over the last few decades. The development of desalination units in the southern coasts of Iran, is considered as one of the main solutions for sustainable water supply. In this research, by studying the three leading countries in seawater desalination, the improvement path of their facilities have been evaluated, and optimal model for the development of desalination units in Iran has been presented. According to the results, four challenges of salty wastewater, damage at the inlet, high energy consumption and the poverty of minerals is observed in desalinated water. Based on the findings, increasing the country's current capacity in seawater desalination from 585,000 to 1,150,000 m3/day is needed to sustainably supply the drinking needs of water-deficient provinces. Based on the economic analysis, including the price of subsidized electricity in Iran, the total price of each cubic meter of water for near the coast, Kerman, Yazd and Birjand is estimated to be 432, 702, 972 and 1026 thousand Rials, respectively. Also, in terms of salinity and environmental issues, the location of sweetening units on the coasts of Makran has an advantage over the Persian Gulf.

Adverse environmental impacts of desalination plants are barriers for their development. Nevertheless, current Environmental Impact Assessment (EIA) methods cannot provide a suitable quantitative framework for comparing and evaluating different practices or strategies. This study introduced a quantitative method based on midpoint and endpoint ReCiPe coefficients used in Life Cycle Impact Assessment (LCIA). Accordingly, both direct and indirect environmental impacts of seawater desalination on humans, terrestrial and marine ecosystems were calculated and compared for coastal and inland operating conditions. The impacts of using renewable energies and Zero Liquid Discharge (ZLD) systems were also compared by the proposed methodology. For this purpose, the available brine water quality data of operating RO and MED plants located in southern Iran and the Middle East were used. Results showed that LCIA method can properly account the accumulated environmental impacts of desalination. In addition, this research highlighted that the main damage of desalination plants on marine and terrestrial ecosystems is originated from discharging toxins and hazardous wastes through brines. Consequently, it is emphasized that brines should be carefully monitored based on their toxicity. In addition, due to 70-80% effectiveness of ZLD on environmental impact reductions, its application should gain the highest priority for environmental protection.

Due to the lack of fresh water, production of potable water is one of the important issues for mankind. Capacitive deionization is one of the methods that has recently attracted the attention of researchers due to its simplicity, low price and low energy consumption. The main challenge of this method is high energy consumption at high water concentrations. Therefore, this paper aims to investigate the effect of different effective parameters to improve the system performance. These parameters include feeding voltage, process time, electrode surface area and its capacitance value, overall transfer coefficient, volumetric flow rate and concentration of the feed water, and micropores’ volume, whose effects on energy consumption and number of cycles required to produce potable water are investigated. Results showed that the electrode capacitance and micropores’ volume decreased the necessary process cycles (reducing desalination process time) to produce potable water without significant changes in the energy consumption. The feeding voltage, volumetric flow rate and concentration of the feed water significantly affected the process time and energy consumption. For feed water concentration between 5 and 25 mM, results showed that the minimum values for the desalination process time, electrode surface area, and overall transfer coefficient, are 400 s, 50 cm2 and 0.9 µm/s, respectively. To improve the performance of desalination process in the capacitive deionization cell, development on the physical properties (increasing micropores) and the electrical properties (increasing capacitance value) of the electrodes, as the most important parameters, is suggested.

Global water demand is constantly increasing, while freshwater resources are limited due to increased demand and the effects of climate change, especially in arid and semi-arid regions such as Iran. The cost of water production is one of the most important factors in choosing a desalination method. In the adsorption method using natural materials, the cost of desalination can be reduced. In this study, Iranian zeolite and bentonite were used to reduce salinity by batch test. The adsorbents were identified by EDx, XRD, and BET. Clays were also modified with 1 M hydrochloric acid. The results showed that Iranian zeolite and bentonite used in this study as mineral adsorbents do not have the efficiency to reduce salinity and increase the electrical conductivity and sodium content of water. The highest increase in sodium concentration in samples was related to natural bentonite (102.5 mg/g) at the highest salinity concentration (64000 mg/L) and the lowest increase in sodium concentration was related to natural zeolite at 0.066 mg/g in the lowest salinity concentration (640 mg/L). Also, the highest increase in electrical conductivity was related to natural bentonite with an increase of 4.3 dS/m. It is noteworthy that after acid correction, the amount of electrical conductivity increased significantly in both clays. Therefore, due to the differences between the clays, it is better to first examine them in terms of construction and then use them in the field of desalination.

Over the last few years, our country has been facing to the water crisis. Therefore, this is important and necessary to creating a fair balance between available freshwater resources and the amount of demand and consumption in communities. That is why water resources proper management and advanced methods development has an essential role in the supply of freshwater. The purpose of present research is to evaluate the quality of the water in the Qanat of the Tabriz University and provide a suitable purification system for the exploitation of that water in the sports complex of the university to properly water resources management and reduce consumption. For that goal, in the first step, according to the results of qualitative experiments of Qanats water, 18 scenarios were proposed, for comparing and choosing the best candidate, it has been taken four main criteria and 13 sub-criteria. In this study, multi-criteria group decision making, TOPSIS method, and Simple Additive Weighting method (SAW) have been used. Which GFDM software has been used to analyze multi-criteria group decision making. Finally, according to the decision makers’ results, the value of each criterion was calculated and analyzed; and it was found that the H scenario was the best choice of the decision makers' point of view was reverse osmosis as a desalination method, sand filter, cartridge filter, and ultra-filter was the best choice for pre-treatment and chlorination.

Today, water desalination methods are of great importance in solving the freshwater crisis in the world, so that in recent years, the world's water desalination capacity has increased dramatically. Among them, the reverse osmosis membrane technology has been the most popular and the most commonly used. There are problems such as high energy consumption, high operating costs, and fouling in this method. The objective of this paper was to use reverse and forward osmosis membrane methods simultaneously in a hybrid reverse-forward osmosis setting, which enabled us to take advantage of the benefits of forward osmosis such as not being dependent on high hydraulic pressure, lower cost and less membrane fouling compared to reverse osmosis. Another objective of the study was to evaluate the permeate water production efficiency of desalination with this hybrid method. It is expected that using the hybrid method will reduce the required pressure for conducting reverse osmosis process to achieve a specified permeate flux, because it reduces cost and energy. An HRFO laboratory pilot with a capacity of 50 m3/day was designed and set up in the Hydraulic Lab of Shahid Chamran University of Ahvaz for running hybrid experiments. The design of the pilot was such that it could operate in both reverse osmosis and HRFO. HRFO experiments were carried out at pressures of 4.5 to 10.5 bar for Ahvaz urban water as feed solution, as well as NaCl as draw solution with a concentration of 2000 to 10000 mg/L via the experimental HRFO plant. It was found that adding the forward osmosis to reverse osmosis at the best situation (lowest pressure and highest concentration of draw solution) can increase the permeate water production efficiency of desalination by 55.12%. The best hybridization degree of these two methods was determined to be 64.5% for reverse osmosis and 35.5% for forward osmosis.

Freshwater limitation as one of the most important challenges of water resources management of the country has caused seawater desalting to be considered a suitable option for utilizing non-conventional water resources in some parts of the country. Due to the lack of a comprehensive understanding of the environmental impacts of desalination plants, this study was carried out to investigate the potential environmental impacts of the Kangan desalination plant. In this study, the Life Cycle Assessment (LCA) method was used. So, after preparing an inventory of materials and energy at all stages of freshwater production in the Kangan desalination plant, impact 2002+ version (2.15) as impact assessment method and SimaPro9 software were used to investigate environmental impacts of all stages of seawater desalination process on impact categories, including: global warming, reduction of non-renewable energies, ozone layer depletion, aquatic and terrestrial ecotoxicity, etc. Based on the results, most of the environmental impact is related to climate change and reduction of primary resources. So that, 3.224 Kg carbon dioxide equivalent has been released and reduced 55.035 MJ in primary sources to produce 1 m3 of desalinated water. Also, electricity supply through desalination cycle stages had the most contribution on all impact categories except ozone layer depletion and eutrophication. Due to the maximum contribution of energy on environmental impacts of seawater desalination process, utilization of renewable energy sources can play an important role in reducing the environmental impacts of these plants.

Increasing water demand and limitation of accessing to freshwater resources have been caused using of seawater desalination in most countries, especially arid and semiarid regions. Duo to the importance of environmental impacts of desalination plants, the present study carried out to comparing the environmental impacts of Chabahar and Kangan desalination plants. Desalting methods is reverse osmosis in both plants. The extraction of the raw seawater in the Kangan plant is beach well intake which supplying indirectly from Persian Gulf and in Chabahar plant is open intake and supplying directly from Oman Seawater. Therefore, the Life Cycle Assessment (LCA) method was used. After preparing a complete inventory of materials and energy at all stages of freshwater production, the environmental impacts of all seawater desalting processes on different environmental impact classes were evaluated using Impact 2002+ version (2.15) and SimaPro9 software. After preparing a complete inventory of materials and energy at all stages of freshwater production, the environmental impacts of all seawater desalting processes on different environmental impact categories were evaluated by using IMPACT 2002+ version (2.15) and SimaPro9 software. According to the results, the greatest impact on both plants were climate change and reduction of primary resources. So that, equivalent 3.224 and 3.627 Kg carbon dioxide has been released and reduced 55.035 and 61.928 MJ in primary sources, in Kangan and Chabahar plants, respectively, as producing 1 m3 of desalinated water. Therefore, it seems that using beach wells intake to extracting seawater in desalination plants is more appropriate.

Generation of electrical energy requires water as well as water conveyance and treatment to energy. For encounter to challenges and uncertainty about the water and energy nexus, requires to understand the nature of this linkage to identify, approve and execute the appropriate policies. The aim of this study is the evaluation of water and energy nexus at freshwater production by SWRO desalination. For this purpose, assuming that the electric power supplier for the desalination plant is a thermal power plant with a cooling tower or once-through-cooled, the specific water withdrawal in a thermal wet tower- and once-through-cooled plants using S-GEM model and specific energy consumption in RO plants using solution–diffusion model was calculated. The results indicate in the production energy sector, the practical power effect on fuel consumption and consequently water withdrawal. Also, in the desalination plant, the physio-chemical parameter, and temperature of feed water, and ERD type effect on specific energy consumption. Finally, the indirect volume of water withdrawal, fuel and thermal energy consumption to produce a cubic meter of desalting water was obtained which could be used by effective institutions to better manage the supply and demand of water and energy.

The need for freshwater is rising rapidly, and fresh water resources cannot meet all human needs. People's access to freshwater is now diminishing with the increasing population and expansion of cities. Accordingly the desalination of sea water has become increasingly important and selection and development of more efficient and cost-effective desalting process is a necessity. The present study was designed to optimize the operating conditions to reduce the effect of external concentration polarization on the performance of direct osmotic process. Due to the number and variety of parameters affecting the amount of water flowing through direct membranes and also with the aim of reducing the number of experiments and costs, the Taguchi experimental design method was used. The structure of membranes was investigated using scanning electron microscopy (SEM). The best performance of direct membrane was observed in membrane No. 1 with test conditions, concentration of molar salt solution, pressure head of 2 psi and pH = 9. In this condition, the flow rate of the flow through the direct osmosis membrane was 36.42 L/m2.h. The highest flux of salt passing through direct membranes was 26.11gr/m2.hr in test conditions and with the concentration of molar salt solution, the pressure head of 2 psi and pH =9. By optimizing the operation conditions, 55.51 perecent increase in the water flux was observed

Nowadays, increasing population and reducing fresh water resources, needs to introduce seawater as a new water source and sweetening it using new techniques including nanoparticles considered. Mineral clays, such as cationic exchangeable bentonite clays, can exchange their own cations, including calcium and magnesium, with sodium ions of sea water. In this research, Kalkate's bentonite clay was used for seawater sweetening testing and the flame photometer device was used to measure the process of reducing sodium ion from seawater. The results showed using 5.5 gr bentonite with 200 rpm mixing velocity, in a contact time of 15 minute in 20 ml sea water is the optimal conditions for mixing bentonite and seawater. On the other hand, in order to reduce the chloride ions from seawater, MgAl-CO3 layered double hydroxides nanoparticles, was synthesized and used in water quality laboratory of the University of Zanjan. The results of  this experiments also showed using of 1.25 gr LDH with 200 rpm mixing velocity, in a contact time of 10 minute in 5 ml seawater is the optimal mixing conditions.

Water desalination systems is among the methods used to produce potable water to be used for domestic, agricultural and industrial applications. Reverse osmosis is a common methods employed for desalination facilities, mainly because of its low energy consumption, and high efficiency for permeate production. The main aim of this research is to use nanocomposite containing carbon nanotubes to improve membrane wall performance. in addition, the increase in the flux as a result of decreased clogging surface on the membrane was also studied. To accomplish the objective of the study, the synthesized polyamid reverse osmosis nanocomposite membrane were used for purification of brackish water with the characteristic of having the electroconductivity of 4000 µs/cm. The modified raw-multi walled carbon nanotubes membrane was embedded through polymerization method in order to increase porosities and hydrophilicity. Analysis of Contact angle, SEM, FTIR and AFM were done for recognizing the compounds which were created on the surface of membranes and membranes hydrophilicity. Three sets of samples were prepared for testing in the membrane cell synthesis analysis. Water flux and rejection rates were assessed every 30 minutes. Results of this study showed that the membranes have soft hydrophil surfaces and by increasing nanocomposite concentrations with specified measure, the water flux increased up to 30.8 L/m2h which was noticeable compared to the simple polyamide membranes. Our results also showed that fouling reduced considerably and the clogging condition was reduced by nanocomposite membranes, and the rejection rate was higher than 97 percent for all synthesized membranes with pyrrol.

Condensation Irrigation (CI) is a combination of simultaneous desalination and irrigation/drinking water production. As saline water evaporates in a solar distiller and the hot and humid air is transferred into an underground pipeline, fresh water will condense on the inner pipe surface due to cooling of air by the ground. The water thus condensed infiltrates into the soil through pores in the perforated drainage pipes laid in the ground to transfer the humidified air. In this study, the CI system was developed using common buried pipes to determine the amount of water produced. In this setup, condensed water is collected at the end of the pipe to be used for drinking. Observations and calculations indicated a mean water production capacity of 4 liters every 8 hours along a pipe 25m long. Less water was produced on the first day because some of the water was lost to the wetting of the internal pipe walls. Finally, examination of temperature effects revealed that water production along the pipe reduces as we move farther away from the inlet part of the pipe.

Seawater desalination is recently considered as an important source for providing drinking water largely due to the increased water consumption as well as depletion of available and accessible water resources. This is especially important in case of Iran which is located in an arid region facing the challenges of water resources shortage. Due to the progressive development of seawater desalination processes, the discharge of brine can potentially bring about physical, chemical, and ecological effects on the environment of receiving water resources. Therefore, the necessity of more accurate and better understanding of such effects and different aspects of desalination processes as well as the brine as the by-product is undeniable. The focus in the present paper is investigation on the effects of brine discharge on the quality of various parameters in the receiving water and providing solutions for minimizing the side-effects. Techniques such as use of cooling water in power plants, combination of brine with municipal sewage, groundwater desalination, and proper selection of sites and discharge procedures are among the practical proposed strategies.

In this study the results of the experiments conducted in surface discharge of negatively buoyant flows in stagnant and non-stratified body are presented. Geometrical behavior of flow have been studied by simulating of discharged in a dark room and digital possessing of the photos. To determine the mixing behavior of flow the data obtained from 20 conductivity probes located along the trajectory of flow were utilized. Flow concentration profiles, flow self similar trajectory, variation in flow width and changes in flow dilution are the flow characteristics that were studied here. Regarding flow self similar properties the non dimensional behavior of flow will show similar behavior for different conditions of discharge. To have a comparative scale the experimental results were compared with the behavior that formerly reported for submerge horizontal discharges of positively buoyant flows. The analysis of flow behavior in these two discharges showed that despite the fact the flow general behavior is similar, geometric and mixing characteristics of flow in surface discharges are different from the those observed in submerge discharges. In surface discharges flow protrudes more in comparison to submerge discharges. The changes of flow width and dilution were also different from the one reported for submerge discharges.