WATER AND WASTEWATER
Year:2019 | Volume:30 | Issue:4 (122) |Papers Count:12

Water crisis and its management techniques in urban water supply systems is a crucial issue. Many different natural and unnatural disasters, including earthquake and terrorist attacks, cause the greatest damages to these systems. Before the crises occur, Prioritizing effective strategies by experts can greatly reduce these damages. In this study, Fuzzy PROMTHEE II method has been used for the ranking of Tehran City’ s water supply risk management scenarios including prevention and preparedness in precrisis conditions, with consideration of experts’ opinions in Tehran Province Water & Wastewater Company. Due to the uncertainties in experts’ opinions and parameters required for urban water supply risk management, fuzzy theory is applied. The results show that the reliability of the water supply and cost of project implementation criteria have the highest importance, respectively. By ranking of scenarios, it was found that measures such as strengthening passive defense in supply and distribution systems, and consumption management and encouraging people to save the emergency water as well as contract with the companies producing water packaging with score of 0. 192, 0. 176 and 0. 132, have the highest ranks among actions before the crisis, respectively. The proposed decision-making model can help decision makers to prioritize drinking water supply scenarios under the emergency conditions.

In recent years, due to excessive consumption and unbalance between water consumption and water resources, Iran has led to a severe shortage of renewable water sources. Therefore, in this situation, analyzing the status and presenting appropriate strategies is the main priority for policymakers. For this purpose, by designing a dynamic stochastic general equilibrium model, status of consumption of water resources has been studied in the household, agriculture and industry sectors. The existence and definite status of the stable situation, both parametric and numerically, has been investigated according to estimated values for Iran's economic parameters. According to the results of the research, it should be noted that at present, per capita water consumption is 1000 cubic meters per year. In other words, with current domestic consumption per capita, water per capita is less than that on the optimal Path. It is expected to achieve sustainable equilibrium in a long-term horizons by reforming consumption and providing policy solutions. Also, based on the simulation, from different policies, Establishing a 8-year limit on agricultural products with high water consumption is the most important policy for achieving the above equilibrium.

Water distribution networks (WDNs) are complicated infrastructures which their construction, operation and maintenance have considerable costs. Since most of the variables effective on the design and operation of WDNs cannot be computed and achieved accurately and definitely, uncertainty subject should be considered as an inseparable issue in the calculation of these networks. In this study, using the fuzzy logic concept and genetic optimization algorithm, the impact of uncertainties of input variables (nodal demands and pipe roughness coefficients) on the results of hydraulic analysis of two sample networks have been examined. In this regard, first, the fuzzy membership functions of input variables have been determined and by considering the simultaneous impacts of these variables' uncertainties, the output variables of hydraulic analysis have been calculated more accurately. Afterwards, variables of pressure, velocity and energy loss have been considered as representers for evaluating the hydraulic performance of network elements (nodal demand and pipes). In order to calculate the hydraulic performance indices of these elements, after analyzing the network based on the pressure driven simulation method, penalty curves defined according to the available standards, have been employed and the obtained results have been compared to the results of the demand driven simulation method. In addition, a new relation for combining the performance indices of network elements and obtaining an index for evaluating the total pipe performance and calculating the total hydraulic performance index of network has been introduced. According to the obtained results, slight uncertainties in the input variables of hydraulic analysis lead to high uncertainties in the outputs of the hydraulic analysis of WDNs. Meanwhile, velocity in pipes more than nodal pressures are affected by the uncertainties of input variables of hydraulic analysis. Also, implementing the pressure driven simulation method in performance evaluation of WDNs in their operation period leads to more reasonable and real results. For instance the total performance of network was 0. 56 for 9-loop network and was 0. 26 and 0. 59 for 2-loop network, respectively, based on demand and pressure driven simulation methods.

The hydraulic jump has many usages in transport and treatment of water and wastewater. It may be considered macroscopically as a rapidly varied flow with strong vortices which generate macro turbulent fluctuations. The pressure fluctuation due to turbulence must be carefully considered in designation of hydraulic structures. In addition, cavitation, abrasion, and vibration due to the intense turbulence and pressure fluctuation may also contribute significantly to damage of a stilling basin. This paper discusses the characteristics of pressure fluctuation in submerged hydraulic jump downstream of spillways and also the effects of submergence ratio on the pressure fluctuation. The experiments were carried out in a rectangular conduit (constituted from a30o spillway, 1. 8m in height and a horizontal flume with 0. 3m width and 3m length), for the Froude number of 7. 07 and also different ratios of submergence. Pressure data were recorded by pressure transducers having sampling rate of 100 Hz. Experiments show that intensity of pressure fluctuation on the hydraulic jump bed is a function of Froude number a relative distance from basin’ s beginning and submergence ratio. Increasing submergence ratio decreases the coefficients of pressure fluctuation (C􀭮 􀬿 , C􀭮 􀬾 , C􀭮 􁇱 ), so that increasing the s. r. from 1 to 2, the C􀭮 􀱣 􀱗 􀱮 􁇱 decreases 89%. Also, the coefficient of standard deviation C􀭮 􁇱 and the extreme coefficients of pressure fluctuation C􀭮 􀬿 and C􀭮 􀬾 decrease by increasing the s. r., and maximum value of C􀭮 􀬿 and C􀭮 􀬾 occurs in the range of X/Y1  20. Therefore, this range has more importance from the structural designation view and the higher ratio of submergence supports the higher confidence for designation.

Dye content of the textile industry wastewater has either chemical structure resistant against the purification processes such as physical, chemical and biological treatment methods or low removal efficiency. Thus, alternative methods must be used in order to remove the organic compounds of these effluents. In the present study we used bismuth oxide nanoparticles to remove the organic compounds from effluents of Ardabil Textile Factory. in the present study in order to use nanoparticle technology to remove organic compounds, firstly sol-gel method was used to synthesize the bismuth oxide nanoparticles, which were examined using XRD, FESEM and DRS techniques. Then, the nanoparticles were examined for their sonocatalytic and photocatalytic activities in the process of removing the organic compounds from the effluents of Ardabil Textile Factory. Results showed that compounds such as n-Decane, n-Dodecane, ntetradecane and Hexadecane accounted for up to 70% of the abundance of chemical compounds. In the nanoparticle-free sample subject to ultrasonic waves, the removal rate of the chemical compounds including n-Decane, n-Dodecane, n-Tetradecane and Hexadecane was as low as 2. 86%, 6. 25%, 8. 33% and 25%, respectively. In contrast, in the sample containing nanoparticles subject to ultrasonic waves the removal rate for n-Decane and n-Dodecane was as high as 92. 14% and 95. 13%, respectively, for n-Tetradecane and Hexadecane was over 99%. In the sample subject to UV and in the presence of bismuth oxide nanoparticles, n-Decane and n-Dodecane was removed by 92. 82% and 93. 75%, respectively, whereas n-Tetradecane and Hexadecane was removed by over 99%. results revealed that US without nanoparticles had a little efficiency in removing the organic compounds. Whereas, both the US/Bi2O3 and UV/Bi2O3 processes had a removal efficiency of over 90%. Thus, adding nanoparticles of Bi2O3 to the effluents can make a substantial contribution to the removal of organic compounds from the textile industry effluents.

In this study, novel polyacrylonitrile/iron nano oxide (PAN/Fe-ONPs) nanofiber adsorbent modified with 2-Amino-3-methyl-1-hexanethiol (AMH) was synthesized by combination of hydrothermal and electrospinning method and evaluated as an adsorbent for removing thorium (IV) (Th4+) ion from aqueous solution. The PAN/Fe-ONPs/AMH was characterized by X-ray diffraction (XRD), Fourier Transform Infra-Red (FT-IR), Scanning Electron Microscopy (SEM), energy dispersive X-ray analysis (EDX) and Brunauer– Emmett– Teller (BET). Response Surface Methodology (RSM) was utilized in the optimization of Th4+ adsorption for parameters such as pH, the initial metal ion concentration (Th4+ concentration) and contact time. For this purpose, the central composite design (CCD) with a predictive quadratic model was applied with 8 cubic points, 6 pivot points and 6 replicates at the center. The statistical measures (i. e., Analysis of variance (ANOVA), R2, the lack of fit test and the P value) specify that the developed model is proper. The results of optimization showed that the adsorption percentage of PAN/Fe-ONPs/AMH for Th4+ under optimal conditions (pH=5. 7, initial concentration 232 mgL-1 and contact time=67. 8 min) was 98% at 25oC. In addition, the adsorption kinetics was well defined by the pseudo second-order equation, while the Langmuir model better fit the adsorption isotherms. The adsorption capacity of PAN/Fe-ONPs/AMH was 472 mg Th4+g-1 composite. The loaded Th4+ can be easily regenerated with HNO3/HCl and the PAN/Fe-ONPs/AMH could be used repeatedly without any significant reduction in its adsorption capacity. Adsorbent recovery by using 0. 4M HNO3/0. 2M HCl solution for adsorbent reuse indicated that the PAN/Fe-ONPs/AMH adsorption capacity for Th4+ was decreased by about 7. 5%.

Antibiotics are organic pollutants that are introduced into surface water and underground water sources due to urban and industrial effluents. Due to their high stability, they do not only disrupt the common processes of sewage treatment, but also have toxic effects on humans and other living organisms, and their removal have therefore been considered. This is an experimental study in a laboratory scale with the aim of evaluating the efficiency of the new FeNi3/SiO2/CuS magnetic nanocomposite for the decomposition of metronidazole in the presence of H2O2 as a heterogeneous Fenton-like catalytic process in aqueous solutions. In present study, firstly, this nanocomposite was synthesized and characterized by FESEM, TEM, FTIR, XRD and VSM. This study, which was performed on synthetic sewage in batch system, parameters such as pH (3, 5, 7, 9 and 11), nanocomposite dose (0. 005-0. 1 g/L), metronidazole concentration (10-30 mg/L) and the concentration of hydrogen peroxide (50-200 mg/L) at ambient temperature was investigated. The obtained results showed that the highest percentage of removal of metronidazole in pH =7, nanocomposite dose (0. 1 g/L), hydrogen peroxide concentration of 150 mg/L for 20 mg/L contaminant concentration at time of 180 minutes, 77. 92%. Also, the kinetic rate of degradation flowed pseudo-first-order equation (R2=0. 95) and the degradation constant rate of this reaction is 0. 0038 (1/min). Based on the results obtained from this study, it can be concluded that Hentrogenase Fenton like catalytic process has a very good effect in removing metronidazole antibiotic contamination from aqueous solutions.

Textile industry wastewater in additions toxicity for organisms led to changes as decreased of water transparency and sunlight penetration and increase in chemical oxygen demand. Therefore, this study was carried out with the aim of removal of cationic red 46 dye from aqueous solution. For this purpose, the magnetic polymeric composite of graphite oxide nanoparticles (GO) and magnetic nanoparticles (MNP) in the matrix of polyacrilonitrile fiber (WPAN) at micro size by electroespining method was prepared. The XRD and SEM tests were used to determine the polymeric adsorbent characteristics. Magnetic properties of magnetic nanoparticles and polymeric adsorbent were measured at using vibrating sample magnetometer (VSM) analysis. Batch adsorption tests were optimized using the L16 orthogonal array of Taguchi method. The effects of variables including pH, adsorbent dosage, initial dye concentration and contact time on the dye removal were examined and the most influential factor in the removal of dye was pH. The adsorption isotherm data were well-fitted to Freundlich isothermal model (R2= 0. 99). Furthermor, adsorption kinetics of the dye followed pseudo-second-order model. Basic on these results, the polymeric composites was effective adsorbent for dye removal with efficiency over 96% and with quick separation for dye removal from aquatic solution.

Over the past decades, the sharp increase in population growth and industrialization in developing countries has reduced the quality and quantity of water resources. Water Treatment and purification technologies are rapidly developing in membrane separation processes. In this study, the effect of anionic and cationic surfactants on the performance of polyamide membrane nanofiltration was investigated experimentally. Nanofiltration membranes were constructed by adding anionic surfactant Sodium Dodecyl Sulfate and Hexadecyltrimethyl ammonium bromide cationic with a filming machine. The highest percentage of salt excretion related to the polyamide nanofiltration membrane without adding surfactant with the amount of 16. 19% at 180 minutes. Also, the greatest amount of water flowing from the polyamide nanofiltration membrane is related to the time of 30 minutes and the state where the anionic surfactant is added to the membrane by weight of 10%. In this case, the amount of water flowing through the membrane of polyamide nanofiltration was 37. 76 L/m2. When anionic surfactant was added to the membrane at a rate of 10%, the membrane water flux was 41. 48% higher than the pure membrane (no additive).

Quality assessment of the groundwater resources is one of the most important issues in water resources development. The main purpose of this study is to model the nitrate pollution, to recognize the spatial and temporal variations of nitrate concentration and to predict the nitrate movement under hydrological gradient. Thus, collecting and organizing the field data, formulation of hydrodynamic characteristics and transmission phenomena was conducted for the aquifer system in Varamin plain, Iran. In this study, a quantitative model of GMS software was prepared using MODELFLOW code and the qualitative data was imported to the model. The MT3D was used for modeling. According to the modeling results, it is predicted that during a 10-year period water from some zones of the aquifer will become non-potable. The most important factor in degrading the water quality in downstream of cities is the nitrate pollution from absorbent wells in residential areas in addition to the nitrate pollution from the agricultural areas in upstream. Due to the existence of an impermeable layer, confined aquifer is less affected by nitrate pollution in Varamin plain. According to the quality standards for drinking water, this aquifer is in an appropriate condition. It is suggested that drinking water be supplied from the wells recharged by the confined aquifer.