جستجوی مقالات مرتبط با کلیدواژه « تصفیه آب » در نشریات گروه « آب و خاک »

In recent years, the consumption of antibiotics has increased significantly all over the world due to health reasons related to human and animal health. The presence of these compounds even in very small amounts causes adverse effects on the environment and living organisms. The purpose of this study is to review different technologies for removing antibiotics from aquatic environments with an emphasis on new technologies.

In this study, a review of library studies and articles in the Google Scholar, Science Direct, Springer, Scopus, Elsevier, and PubMed databases are used to obtain up-to-date and valid content.

The results showed that membrane bioreactor systems among biological methods, despite the high cost due to the use of filtration, produce higher quality wastewater and are more effective than other biological treatment systems. Also, the investigation of biological methods showed that the efficiency of removing antibiotics varied from 40 to 95 percent. In recent years, advanced oxidation methods are a suitable option for removing antibiotics, which can completely remove antibiotics, and are also a cheap and environmentally friendly technology. In this study, several antibiotic pollutant purification technologies and their advantages and disadvantages were examined and it was shown that biological and physicochemical technologies, especially advanced oxidation processes, are capable of removing pollutants. They are medicinal. Although photo catalysts have been successfully developed for wastewater treatment on a laboratory scale, more extensive research is needed before the commercialization of these processes.

One of the main limitations in the development of the aquaculture industry in Iran is access to fresh water with good quality. This requires the development of sustainable technologies for aquaculture wastewater treatment. The present study investigates breeding technologies in order to save water consumption in Iran's aquaculture systems, relying on the model of sustainable development. In this research, the innovations created in aquaculture wastewater treatment in recirculating aquaculture systems (RASs), aquaponics and integrated multi-trophic aquaculture (IMTA) systems have been discussed. A recirculating aquaculture system, which treats wastewater by removing toxic pollutants and recycling water, requires only 10% of the total volume of fresh water to produce of fish. Therefore, this system helps to save water. However, it has limitations, the most important of which is the accumulation of nitrates in the system, high economic cost, and difficult management, which is achieved by converting nutrients from aquaculture effluents into algal biomass. In addition to RASs, aquaponics is a food production system that combines conventional aquaculture methods and RASs. This method includes aquaculture and plant cultivation, which shows the integration of aquaculture-agriculture activities. Integrated multi-trophic aquaculture (IMTA) includes the use of symbiotic organisms in breeding systems that optimizes the balance of nutrients and purifies the wastewater resulting from aquaculture activities. This method shows the combination of different nutritional levels that organic and inorganic effluents are used by different organisms.

Water is the source of life and the main building block of the universe, which is also the most consumed beverage in the world. Water contains various ions, such as nitrate, nitrite, fluoride, sulfate, chloride, calcium, magnesium, etc. Further, the type and amount of species in water might affect water quality and human health. Today, the high amount of nitrate in drinking water is one of the main public concerns in the health section. Therefore, World Health Organization (WHO) and National Standard Organization of Iran have set the permissible nitrate levels in drinking water at 45 and 50 mg/L, respectively. Nitrate removal from drinking water is necessary to ensure the supply of safe water and prevent the spread of various diseases affected by high amounts of nitrate. In the human body, nitrate has reduced to nitrites that are combined with hemoglobin, which then leads to the making of methemoglobin, which is deadly for babies. Long exposure to nitrate and nitrite leads to the formation of the carcinogenic compound nitrosamine. On the other hand, nitrate affects the size and function of the thyroid gland. Based on the initial quality of water, the level of application scale, the conditions of access to materials and equipment, the cost of the method, and the Type of application of water consumption, different methods are used for nitrification.To investigate the methods used to reduce or remove nitrate ions from water, a comprehensive study was conducted on the basis of reports and research of various scientists in the last two decades. The collected reports were categorized and the characteristics of each method were precisely evaluated separately. Then, the advantages and disadvantages of each method were compared with other methods presented. The most important methods for nitrate reduction are as follows: Ion exchange, Reverse osmosis, Adsorption, Electrodialysis, Chemical, and Biological method. Each of these techniques has its own advantages and disadvantages and different factors, such as economic explanation, industrial application, efficiency, selectivity, and lack of polluting the environment determine the selective method.Among the various methods, the ion exchange method is an effective, simple, relatively low-cost method to reduce the amount of nitrate in water that has good efficiency, especially for low volume water sources. This method involves passing water containing nitrate through a resin bed consisting of anion exchange resins in which the nitrate ion is exchanged with anions such as chloride and has a removal efficiency of more than 90%. In addition to salts and ions, the reverse osmosis method can remove suspended solids, organic matter, colloids, bacteria, and viruses. Generally, reverse osmosis units in the pressure range of 300 to 1500 psi might remove nitrate ions from water. In addition to the mentioned method, ease of execution and uncomplicated design have made adsorption a cost-effective method for nitrate removal. Furthermore, various chemical processes, including electrochemical reduction methods, are used to remove nitrate ions. In these methods, common reducing agents such as active metals, ammonia, borohydride, formate, hydrazine, hydroxylamine, hydrogen, and iron are used.The electrodialysis method purifies water by selectively removing undesirable ions through a semipermeable membrane. In this method, the reduction of nitrate concentration strongly depends on the applied current. The results showed that the optimal current of 20 volts and a concentration of 500 mM electrolyte leads to a significant increase in nitrate removal.The biological method of nitrate reduction is based on the use of nitrate-free microbes, which uses nitrate as the final electron receptor, organic and inorganic materials as electron donors, and energy sources as a way to maintain microbial growth. Bio nitrification is of two types: heterotrophic and autotrophic. The heterotrophic nitrification method is more economical than the autotrophic method on a larger scale and has the possibility of reducing nitrate to nitrogen gas with higher selectivity.The need to reduce or eliminate nitrate from drinking water to prevent various diseases in humans is an important factor in studying and updating nitrate removal techniques. In this study, an attempt was made to offer a variety of methods for nitrate removal, their mechanism, examples of studies, reflecting the properties, and finally, a brief comparison of methods, to provide a basis for studies to introduce and innovate in nitrate reduction techniques. An appropriate understanding of the features of the methods used will save time and cost, improve results, and observe the standards of the World Health Organization. After reviewing and comparing the studied methods, it would be stated that Ion exchange, Reverse osmosis and Electrodialysis are more efficient, compared with other methods, to remove nitrate from drinking water. High efficiency, being user-friendly, environmental considerations, and using at industrial scale are among the most favorable and common properties of these methods.

The use of drip irrigation systems in agriculture is associated with several problems. Clogging of filters and drippers and, thus reducing the uniformity of water distribution needs to be addressed. Proper design and construction of the filter can be one of these suitable solutions to the problem. In this study, a physical model including a filter tank with a height of one meter and a diameter of 60 cm for placing sand with different sand size and thickness of different layers along with a pump, a power of 0.5 horsepower to provide pressure, two pressure gauges were used to determine the hydraulic load losses in the sand filter and, raw water of specified quality. 9 treatments of granulation and layering and, two treatments of water quality containing the amount of suspended solids were used. The aggregation of these treatments was 1.77, 0.89, and 0.45 mm, respectively. The results showed that the load loss changes in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45–0.89 mm. the load loss increased with the smaller particle size of sand. The results showed that the percentage change of filtration in the granulation range of 1.77 - 0.89 is less than the range of 0.45 - 0.89 mm and with increasing the height of the middle layer, the percentage of filtration of filters increased. The results showed that the percentage change of filtration in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45 - 0.89 mm. The percentage of filtration increased with increasing the height of the middle layer. But, the changes in the percentage of filtration for changing the height from 12 to 17 cm were more than the changes in the percentage of filtration from 17 to 22 cm. Clay particles, plant debris, insects are water-soluble substances that must be refined by filters for drip irrigation.

Todays, the application of science and advanced technologies, the management of quality risks imposed on environmental resources, has particular importance. Considering the toxicity of wastewater agricultural, industrial, and domestic effluents on the environment, a thorough and separate study of the toxic wastewater treatment and contaminated water, in general, seems necessary to complete the non-destructive development process. In this regard, to recover compounds containing heavy metals and pollutants such as copper, in wastewater containing harmful fertilizers and pesticides, the production of nanofibers (polymer nanoparticles) in the form of electrospray (under four treatments of solute concentration, applied voltage, Injection Needle and Injection rate), using electrospinning machine and selected polymeric Polyacrylamide Methacrylate and Dimethylmethyl Formamide solvent with using the low-cost raw materials approach for the selected hazardous pollutants. The nanoparticle production technology was used in the form of wire blasting (under four concentrations of nanoparticle solution concentration, the diameter of carbon wires used, flow and arc force), also. Finally, by extracting the results in each phase, their analysis was carried out and the results showed that the combination of the polymer treatment with dimethylformamide solvent at 25 wt%, applied voltage kV. 30, the distance between the tip of the needle and the plate 15 cm and the feeding rate of 2 ml / h worked best. Thus, with the preparation of nanofibers and the use of relatively inexpensive laboratory materials, compared to the costly methods of water treatment, significant results were observed in the process of removal of toxic copper > 50% in all selected samples indicated a positive and high effect of the nanoparticles-nanofibers.

Increasing freshwater consumption caused to reduce renewable freshwater resources in recent years, and one of the basic strategies would be use of non-conventional water resources. Arsenic is one of the natural elements widely distributed in the Earth’s crust. It is commonly found in compounds with oxygen, chlorine, or sulfur, which generally contain inorganic arsenic compounds. Arsenic organic compounds also contain hydrogen and arsenic carbon. There are several methods that can limit the amount of arsenic in water and wastewater; one of these methods is surface adsorption. In this process, any solid that tends to absorb the fluid environment on its surface is considered as an adsorbent. Absorption capacity, selectivity, reproducibility, kinetics, compatibility, and cost are the most essential characteristics of the adsorbent.

In this study, activated carbon derived from agricultural waste was used as tertiary treatment. The heated coal powder used in this study was obtained from the almond and walnut peel waste (from Tuyserkan city of Hamedan province). Activated carbon powder was used in laboratory-scale experiments and was performed for arsenic removal from synthetics samples. Physically activated carbon was obtained and then chemically activated by acidification. Characterization tests (i.e., XRD, FT-IR, BETand SEM tests) were carried out on both types of the adsorbent. Arsenic removal was carried out in batch experiments. The effect of laboratory parameters (i.e., contact time, pH, adsorbent dose, and initial concentration) on the removal process was studied. Experiments are carried out step by step, and after optimizing each parameter and keeping the other parameters constant, all the parameters are optimized accordingly.

The contact time for the adsorption process was considerably decreased in comparison with previous studies. Kinetic and equilibrium studies showed that the adsorption process followed by Langmuir isotherm and second-degree kinetic models. Chemical activation, improved performance, and characteristics of the adsorbent. Acidified charcoal and raw charcoal were compared, and it was found that acidic charcoal had the finest cavities and had a uniform distribution. Although the volume of the cavities has not changed significantly, the structure of the cavities has changed substantially, with the most enormous volume of cavities (0.5 cm3 / g) being less than 5 nm in diameter and the average diameter of the cavities Decreased by 2 nm. According to the results of the Coal Structure Morphological Survey (SEM), in crude coal, the cavities have large openings. Their number is small, but in acidified coal, the number of cavities is increased, and the surface area of the coal is high. The high internal surface area and the presence of microstructural cavities lead to high adsorption of arsenic at the acid-adsorbed sites. With increasing contact time from 0 to 3 minutes, the removal rate of arsenic increases, and after 3 minutes to 10 minutes, it grows with a low gradient and then the removal percentage slightly. In other words, after 10 minutes, there is a balance between the solid and liquid phases. The arsenic removal rate reaches 90% at the third minute and 100% in approximately 13 minutes. As the retention time increases, the contact time of the arsenic with the adsorbent increases, and the adsorption rate increases as the opportunity for contact with the adsorption sites increases. Due to the high specific surface area of the adsorbent and its morphological characteristics, the removal rate reaches 100% with time.

The XRD experiment shows that improved coal is closer to the stable structure than the raw coal. According to the FT-IR experiment, the acidified charcoal decreased the oxygen and aliphatic functional groups and increased the hydrophobicity of the charcoal. The BET experiment revealed that the cavity surface size increased, and the cavity diameter decreased. The cavity distribution was such that the largest volume of cavities was in the range of nanomolecular size. The SEM image also shows an increase in the fine cavities. As a result, the adsorbent has a good morphology and reduces the adsorption time. Also, its special surface is high and has uniform cavities distribution, which can be one of the main causes of high removal percentage. The results showed that at concentrations of less than 120 µg / L and 10 min retention time, the removal rate was 100%. At higher concentrations, drinking water standards can be reached by increasing the retention time or adsorbent dose. The rate of uptake depends on both the concentration of arsenic and the amount of the adsorbent

The lack of water for humans and the environment is one of the serious problems of today's world. Drinking water in Sari city and its dependent villages are provided with groundwater. The poor quality of the outlet water after the pressurized sand filters in the Moallemkola water treatment plant led to investigate the effective factors on the efficiency of the above filters. The pressurized sand filters substrate was composed of three types of silica granulation. This research investigated the physical and chemical parameters of pressurized sand filters by choosing the type of granulation and the use of a single layer and double layer in the pressurized sand filters bed (silica, silica-anthracite, and leca-anthracite), as well as changing their surface load in seven steps. Samples were taken in all steps and from five points in the water treatment plant (inlet water, after aeration, at the beginning of the filter operation, at the end of filter function and after chlorination). The results showed that the best option is the simultaneous use of silica and anthracite in the filter bed, employing 1.5 times of surface load in the water treatment plant, along with the use of aeration and sedimentation units. The removal efficiency of turbidity, TDS, TSS, calcium, magnesium and iron parameters was obtained 85.41, 23.54, 56.94, 21.08, 32.28 and 89.47%, respectively. Therefore, the use of double layer of silica and anthracite will increase the quality of water, and it is recommended for areas with high turbidity.

Due to lack of water resources and per capita consumption in Iran, conservation of water resources is one of the most important and basic priorities. Drinking water in Sari city and its dependent villages are provided with groundwater resource. The poor quality of the outlet water especially the high amount of iron after the pressurized sand filters in the refinery of Moallemkola led to investigate the effective factors on the efficiency of the above filters. The purpose of this study is to investigate groundwater resource by changing the bed and surface load of pressurized sand filters to improve the removal of physical and chemical parameters of the water refinery.

In this research investigated the physical and chemical parameters of pressurized sand filters with the change in filter granulation using a pressurized sand filter model and using different substrates (silica, silica-anthracite and leca-anthracite). Samples were taken after treatment at three points in the refinery (at the beginning of the filter operation, at the end of the filter operation and after chlorination) after 4 months. The measured parameters included determination of suspended solids, turbidity, total soluble solids, hardness, calcium, magnesium and iron. The experiments were carried out in factorial and completely randomized design with three replications. Statistical analysis of data was done using SAS software and comparison of means was done by Duncan method at 5 percent probability level.

The results showed that the effect of substrates materials on TSS, Tu, TDS, Ca and Fe parameters was significant at 1% probability level. The effect of sampling point on all parameters was significant different at 1% probability level. The silica-anthracite bed had the greatest effect on the reduction of all parameters, especially the reduction of turbidity and iron content. So that the reduction of turbidity and iron content in the silica-anthracite bed was close to 70% relative to the silica bed. The leca-anthracite bed was better than the silica substrate. The best reduction in chemical parameters of water was related to silica-anthracite in pressurized sand filters with a surface load of 54 cubic meters per hour. The interaction effect of different materials inside the filter and sampling point was also significant at 1% probability level on TSS, TDS and Fe parameters. The results of the comparison of the average of the physical and chemical parameters of the water studied at different points of sampling showed that the output water at the end of the disinfection had the lowest values relative to the water outflow from the filter at the beginning of the operation and the outlet water from the filter at the end of the operation.

The option of using silica-anthracite in pressurized sand filters in addition to improving the water quality, will reduce the cost of operating (maintenance and repair) of the filters.

Due to the scarcity of water resources and significant population growth, water supply has become a challenge. In such circumstances,efficient and cost-effective technologies such as nanotechnology in water treatment is recommended. The latest in water purification, desalinationsystems, Nano-filtration can bepointed. Nano-filtration separation mechanism of the effect of molecular size, The difference in permeability,and solubility of the feed components and electrical interaction between the membrane and ions are present in the feed.The purpose of this study of Nano-filter system to remove contaminants is challenging.This study, using a Nano-filtration system with a nominal capacity of 300 m3/d and Recovery rate of %60,and activated carbon filtration system and sand filterconsists of three vessel was Molasani Nano-filter water treatment plants in 2013. Experiments using the standard method carried out and the results were analyzed using the Excellsoftware.The results showed that the removal efficiency of the system in EC (%98.47), TDS (%98.45), total hardness (%98.74), calcium (%98.55), magnesium (%99.15), chloride (%96.48), sodium (%96.48) and TOC (%98.57) .Due to the low renal solute dissolved in water and the nutritional value of the elements of water, particularly calcium and magnesium and absorption of these elements of water and nutrients through the body is necessary and the relationship between drinking water hardness and reduced incidence of cardiovascular disease in the community is in the long term this can be a contentious issue.

In parts of desert regions in our country, groundwater is the only source of fresh water and due to geological formation, the concentration of hexavalent chromium in groundwater will reach beyond the allowed limits. Furthermore, previous studies showed that hexavalent chromium is a cancerous substance for humans and toxic for other organisms. In this study the removal of hexavalent chromium from drinking water using reclamation method which turns hexavalent chromium into Cr(III) using Fe(II) as a function of pH and amount of Fe(II) injection were investigated. The removal of hexavalent chromium (Cr(VI)) from drinking water using Fe(II) increased at pH 7.8-8.15, then any increase or decrease in pH leaded to decrease in the efficiency of hexavalent chromium removal. The pH adjustments were done by adding Ca(OH)2 Solution and o.lN NaOH. Results Showed that Cr(VI) reduction will be higher if we use Ca(OH)2 solution for pH adjustment instead of O.1N NaOH. Not only Ca(OH)2 solution improves the Cr(VI) removal efficiency but also it increases the final turbidity of water and it should be noticed in drinking purposes. On the other hand, Ca(OH)2 solution can be used because of its safety and lower cost.

Geosmin and MIB are the common factors causing odor in the water. Water treatment plants usually employ the conventional processes such as aeration, coagulation, flocculation, chlorination or ozonation and adsorption as preventive measures to reduce water odor. But each of these processes alone cannot completely remove the smell. The smell of fish, grass and mud greatly depends on the excessive growth of algae in warm seasons. Geosmin is the major cause of water odor in Mashhad water treatment Plant No. 1, which is usually formed when rural, urban and industrial wastewater as well as agricultural effluents, fertilizers and nutrients enter Kardeh Dam and cause excessive growth of algae in hot seasons. As the only existing hybrid system, the present research is financially justifiable in addition to being technically feasible and considering the operational conditions of Mashhad Water Treatment Plant No.1, is the only executable plan. This hybrid water treatment plant employs an ultrasonic system and deep aeration to remove algae. In the deep aeration process using super aerators, pollutants are eliminated in a two-phase air and water process with ascending air currents. Clarifying and final purification is hen carried out with the help of the absorption method and combined charcoal and activated carbon filters installed at the spillway and pulsator outlets. This is the first time the process is proposed and it is able to provide up to 95% reduction in geosmin related pollutions.

Coagulation, Flocculation and Sedimentation are essential processes in water treatment plants. The purpose of this study was to consider the efficiency of natural polyelectrolyte chitosan as a coagulant in water turbidity removal. Chitosan is a cationic biopolymer with high molecular weight that is produced from the crust of crustaceans like shrimp and crab. This investigationwas performed on water samples containing synthetic water turbidity by applying caoline in high, middle, and low turbidities in the laboratory scale. Optimum dosage of Chitosan in turbidity removal of 1000, 500, 100, 50 and 10 NTU were 10, 6.5, 2, 1.5 and 1 mg/L respectively. Efficiency of turbidity removal were 99.77, 99.25, 94.84, 90.96 and 57.50 and optimum pH values were 8, 8, 7.5, 7.5 and 8 respectively. Chitosan has insignificant effect on water pH and its efficiency in high turbiditie's removal is more than its efficiency in lower turbiditie's levels.