WATER AND WASTEWATER
Year:2020 | Volume:31 | Issue:5|Papers Count:15

Transmission of pollutants to high vulnerability groundwaters is significant due to the uncontrolled growth of water harvesting from wells in recent years. One of the significant parameters for the pollutants transfer to groundwater is the presence of colloidal particles. These particles often facilitate the transfer of pollutants to lower soil depths in saturated conditions. However, in particular circumstances, they also delay the transmission of pollutants. Therefore, it is necessary to study the effect of various parameters on the transfer of pollutants in the presence of colloids. In this research, in order to investigate the effect of various parameters and the effect of colloid presence on pollutant transfer, first, a hexavalent chromium transmission experiment was performed in the presence of bentonite colloidal particles in a saturated porous medium column. Then a one-dimensional numerical model has been developed based on threephase equations and interactions of soil, colloid particles, and pollutants in a saturated porous medium. The equations in this research include six differential equations that have six unknown parameters. These equations are solved with finite difference method, which uses two points reverse differential approximation for derivatives of time and central difference approximation for spatial derivatives. The numerical model was calibrated with experimental results with a determination coefficient of 0. 98 and constant coefficients of the equations were optimized. Investigation of the important parameters showed that by increasing the deposition rate of colloidal particles on the solid matrix, less pollutant content was transferred, which is a fact for the effect of colloidal particles on pollutant transport. Also, increasing the rate of pollutants absorption by colloidal particles and increasing the flow velocity, increases the pollutant transport. The results indicated that doubling the hydrodynamic diffusion coefficient of the contaminant and colloidal particles increased transmission by more than 100 times at the beginning of the experiment and by approximately 15% at the end of the experiment. Finally, the increase in porosity increases the gap between the particles and the chromium transmission. The results of this study indicate the significant effect of bentonite colloidal particles in facilitating and enhancing chromium transport in saturated porous media. Also, the diffusion coefficient has the most influence on chromium transport in the presence of colloidal particles in the saturated porous media. As a result, the presence of colloidal particles in groundwatercontaminated environments should be monitored and the effects of parameters in that environment should be determined by modeling to take the necessary measures to control it.

Rivers are the most important water supply resource for the drinkable, agricultural and industrial demands. Therefore, estimation of water quality parameters in rivers is an essential and necessary task. This research applies the Adaptive Neuro-Fuzzy Inference System (ANFIS), the Least Squares-Support Vector Machines (LS-SVM) and the Gene Expression Programming (GEP) for estimation of Total Dissolved Solids (TDS), Electrical Conductivity (EC) and Total Hardness (TH) in the Sepidrood River and a 40 year period. The applied performance criteria are the correlation coefficient (R), the Nash-Sutcliffe model Efficiency coefficient (NSE), the Normalized Mean Squared Error (NMSE) and the Mean Absolute Error (MAE). These methods have high ability for estimation of water quality parameters. The best method is LS-SVM method for estimation of TDS (RTrain=0. 95 RTest=0. 96). The best method is GEP method for estimation of EC (RTrain=0. 94 RTest=0. 95). The best method is ANFIS method for estimation of TH (RTrain=0. 92 RTest=0. 94). This research shows that intelligence methods can estimate unmeasured concentration of qualitative parameters by concentration of other qualitative parameters.

The dramatic decline in renewable water resources, leakage and pollution in water distribution systems has led to a significant increase in the focus on leakage management and control approaches in most parts of the world. For this purpose, water distribution networks can be subdivided into manageable subdivisions with connecting pipes of these subdivisions equipped with flow meters to control leakage and better manage the water distribution network. In the present study, based on graph theory, the concept of District Meter Area (DMA) is expressed. In order to rank the optimal design of the water distribution network, AHP has been used to minimize the balance in the subdivisions, the number of boundary pipes, the number of pipes equipped with flow meters and for maximization of both flexibility and minimum pressure indices. In this paper, by evaluating different algorithms for creating DMAs of water distribution networks, the best method is suggested. Indexes were ranked by studying the experts' opinion and forming the matrix of paired comparisons, so the first rank for maximizing the resilience index IR was 0. 401 and the last one was for minimizing the number of flow meters with a score of 0. 063. Based on the weight and criteria ranking, the water distribution network algorithms were scored. In terms of weighted graph, the highest score belonged to EBC algorithm and the lowest score to FGC algorithm. In terms of the unweighted graph spectral clustering algorithms rank first and FGC and MA algorithms rank last. In the unweighted graph, some algorithms have equal scores, so more indices are needed to compare them. Due to the simplification of the problem and the pairwise comparison of the criteria with each other, according to the experts, this method offers an optimal and desirable result for selecting the appropriate method for converting the water distribution network into DMAs. In this paper, the EBC algorithm with a score of 0. 182 for the weighted graph, the spectral clustering algorithms with a score of 0. 145 for the weighted graph were ranked first.

In this study, a simulation-optimization model is used for multi-period consequence management of sudden contamination in urban water distribution network. The tools used in the management of consequences in this study are to discharge contaminated water by hydrants, to cut or plug the pipes to control the flow path in the network or to isolate the different areas, as well as to switch the pumps on or off to regulate the water flows pressure into the network. EPANET software is used for simulation and single-objective genetic algorithm is used for optimization. In this study, the three objective functions are to minimize system return time to normal situation, minimize the mass of contamination consumed, and minimize the number of infected nodes. Each of the objective functions mentioned is executed for two different management scenarios. In the first scenario, the status of the hydrants, valves and pumps is constant from the beginning to the end of the management period. In the latter scenario, the status of the hydrants, valves and pumps can be changed periodically from the beginning to the end of the management period. The number of decision variables in this study was 54, which included determining whether the hydrants were open or closed, whether the pipes were closed or connected, and whether the pumps were on or off. The contamination loading is injected from the three candidate nodes into the network. The results show that alternating situations of hydrants, valves and pumps, compared to the situation where the hydrants, valves and pumps are in constant condition, decreases the return time to a normal state between 13 and 26. 5 percent, the amount of contaminated water consumed between 12 and 20 percent and the number of infected nodes between 6 and 21 percent. It should be noted that in all scenarios, the minimum water pressure at the nodes of the network is controlled from the minimum permissible value and the increase in the number of management responses actions is controlled from the maximum permissible value. The alternation of the opening and closing of the hydrants and valves, as well as the switching of the pumps on or off, helps to improve the target functions to an acceptable extent.

AjiChay is one of the most important rivers in the Urmia catchment area, which collects relatively large regional waters from the East Azerbaijan province and sends them to Lake Urmia. In recent years, in order to revive Lake Urmia, parts of the river have been rehabilitated and reorganized to transfer water to the main body of Lake Urmia. In this research, the effects of environmental damage on the improvement of the AjiChay River in physical, biological, social, economic and cultural environments were studied and evaluated using two methods of organizing and non-organizing of Pastakia matrix and weighted checklist (scaled). The study of the construction and operation of the project based on the results of the method of Pastakia showed that the positive effects of the project are 61% and its negative effects are 31. 7%, and 7. 3% of the works are not effective. The results of the checklist method also showed that the failure to implement the Aji Chai River Arrangement Plan would result in 13 positive effects versus 29 negative ones. Positive effects are limited to natural and physical environments and biological environments, but negative effects will occur in addition to those environments in the economic and social environments. In general, the results of both methods show that the most positive effects of this plan are related to socio-economic aspects. Ultimately, the environmental impact assessment shows that the Ajichay scheme has succeeded in achieving its primary goals.

Heavy metal pollution in water sources is a great environmental issue worldwide. In this line, Cd(II) is considered to be one of the top toxic heavy metals because it is a threat not only to plants, but also to humans. Accordingly, development of new strategies for removal of Cd(II) is of great importance for scientists. This study could be divided into three overall sections: 1) synthesis and characterization of fibrous mesoporous silica KCC-1, 2) surface modification and characterization of triamine-functionalized KCC-1 (TA-KCC-1), 3) investigation of the applicability of TA-KCC-1 as an adsorbent for the removal of Cd(II) from aqueous solution via adsorption method. Synthesized materials were analyzed and investigated by FTIR, FESEM, and N2 adsorption-desorption isotherms. In order to investigate adsorption features and determine the better adsorption capacity for TA-KCC-1, adsorption conditions such as pH, adsorbent dosage, initial concentration of pollutants, and contact time were monitored and optimized. Then, to investigate and predict the adsorption properties and adsorption mechanism of Cd(II) by synthesized TA-KCC-1, various nonlinear kinetic and isotherm models were used. Theoretical parameters obtained from experimental data revealed that the adoption of Cd(II) cations by TA-KCC-1 follows the Langmuir isotherm model with the maximum adsorption capacity of 378 mg g– 1 under optimum conditions (pH=7. 0; adsorbent dosage=5. 0 mg; time=300 min; temperature=298 K). The results of this study showed that the novel adsorbent reported in this study possesses the high potential for adsorptive removal of Cd(II) from aqueous solution. Also, biodegradability, designability, and high adsorption capacity of this adsorbent may be promising for similar research in the field of adsorption pollutants in the future.

The discharge of dye-containing wastes by the dye-consuming industry causes irreparable damage to the environment and humans. Nowadays, the use of membrane separation technology is a new and applicable technology in dyes separation. However, membranes used in water and wastewater treatment suffer from problems such as permeability-selectivity trade-off as well as short life due to fouling. Therefore, in this study, we tried to improve the hydrophilicity and antifouling properties of polyvinylidene fluoride (PVDF) membranes by adding NiFe2O4-SiO2 nanocomposite and improve its performance in reactive dye separation from aqueous solution. For this purpose, first NiFe2O4-SiO2 nanoparticles were prepared by sol-gel method and then pure and NiFe2O4-SiO2/PVDF nanocomposite membranes were fabricated by wet phase inversion method and their performance was evaluated. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) methods. Membranes morphology, surface roughness, hydrophilicity of the membrane surface, separation performance, pure water flux, porosity and pore radius were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), contact angle tests (CA), pure water flux test (PWF) and gravimetric methods, respectively. Aqueous solution containing 10-30 ppm reactive red 120 was used as test wastewater. The results of the contact angle analysis showed that by addition of 0. 3 wt. % NiFe2O4-SiO2 nanoparticles to the polymer matrix, the membrane contact angle decreased from from 77. 5° in the pure membrane to 51. 7° in the nanocomposite membrane. It showed an increase in membrane hydrophilicity. AFM results showed that the surface roughness decreased as NiFe2O4-SiO2 content increased in PVDF matrix. It was also found that nanocomposite membrane containing 0. 3 wt. % NiFe2O4-SiO2 nanoparticles has the best separation performance among the other fabricated membranes and this membrane can reject reactive red 120 dye from aqueous solution completely (99. 5%).

MTBE is one of the most common hydrocarbon compounds in crude oil that leaks into groundwater through reservoir leaks. The use of MTBE in gasoline compounds has increased significantly and has caused groundwater pollution. In this study, the permeable reactive barrier technology was used to remove MTBE from aqueous solution. In this study, aerogels were used as adsorbents in permeable reactive barrier to remove MTBE from aqueous solution. SEM, BET, XRF and solid addition methods were used to determine the adsorbent properties. In experiments under batch conditions the effect of contact time, pH, adsorption isotherm and adsorption kinetics were investigated. Continuous experiments were studied for determination of bed life and adsorbent performance in PRB. The capacity of this adsorbent was obtained in batch experiments, 6. 25 mg/g Aerogel. The equilibrium time in batch experiments was about 60 min and the optimum pH was about 6. In the adsorption isotherm studies, the Freundlich model and in the kinetic studies, the pseudo-second-order model had the best fit with the data. In this study, the PRB was evaluated by continuous tests. The aerogel adsorbent had an adsorption capacity of 13. 4 mg/g Aerogel (bed depth of adsorbent was 6 cm). Also, the PRB bed life was calculated and determined. The use of Aerogel in PRB was evaluated as an effective agent in MTBE removal.

Nitrate is one of the most widespread water supplies in the world and one of the most important indicators of drinking water quality. So far, several methods have been used to remove organic and inorganic pollutants from water, that has resulted in the increasing application of iron nanoparticles. Therefore, in this study, the effect of acidity and soluble organic matter on the formation and stability of secondary compounds of nitrate reduction by application of Nanoparticles Zero Iron (nZVI) in vitro conditions is evaluated. In this study, the ability of various levels of zero iron nanoparticles to stabilize on gravel particles (1, 1/5 & 2 mg/l) in the complete recovery of nitrate to ammonium and the formation of nitrite in different acidity (3-4-5) and three concentrations of humic acid (0-0/25-0/75 mg/l) was evaluated. Based on the results, the zero-strength iron nanoparticles alone at pH=3. More than 85% of nitrate was restored to ammonium. By increasing the humic acid to the solution, the concentration of ammonium and nitrite increased significantly, which could be due to the oxidation of part of the protein compounds structure of humic acid being in the vicinity of nanoparticles. Nanoparticles Zero Iron (nZVI) not only eliminated nitrate but also removed organic soluble organic matter. Ammonium bands of humic acid are hydrated in the presence of Nanoparticles Zero Iron (nZVI) and part of the ammonium produced at the surface of the oxidation solution. Therefore, with further experiments, it is hoped that the removal of nitrates and soluble organic matter with Nanoparticles Zero Iron (nZVI) from water resources would be possible.

Nowadays, wastewater treatment is important for eliminating organic and inorganic contaminants. Among organic pollutants, colors have a great impact on environmental pollution. Physical adsorption by activated carbons is very useful in removing pollutants and wastewater treatment. In this study, an activated carbon fiber with high mechanical properties and adsorption capacity was prepared through thermal stabilization and chemical activation of acrylic fibers. Nitrogen adsorption/desorption analysis, Fourier transform infrared spectroscopy (FTIR) and measurement of mechanical properties and iodine number were used to investigate different characteristics of the obtained adsorbent. The potential of these new adsorbents for removal of methylene blue (MB) from aqueous solution was investigated in the batch experiments and the influence of main operating parameters, including pH, and the initial dye concentration was studied. Rapid and relatively complete removal (about 95%) of MB dye was achieved at the pH of 12 and initial dye concentration of 100 mg/L. Moreover, it was revealed that the experimental data could be expressed well by the Langmuir and pseudo-second-order model, such that the maximum amount of monolayer adsorption was about 324. 83 mg/g. The thermodynamic parameters indicated the spontaneous nature of the adsorption process. According to all results, the mechanical properties and adsorption capacity of the fabricated activated carbon fibers in comparison with other adsorbents exhibit relatively better properties.

Wastewaters produced from various industries and their entry into surface water is one of the most important environmental problems that have harmful effects on aquatic life. Discharging phosphate from urban and industrial wastewater to the aquatic environment causes a lot of algae growth. The aim of this study was to evaluate the removal of phosphate from aqueous solutions using sepia endoskeleton (cuttlebone) powder as a natural biomass, cheap and non-toxic absorbent. This study was conducted in a batch system. Sepia endoskeleton was washed with distilled water. It was then dried at 80 ° C and thoroughly powdered by milling. Physical and chemical properties of the adsorbent were determined using the Particle Sizer, atomic force microscopy, and infrared spectroscopy and X-ray fluorescence. The effects of variables affecting phosphate uptake, such as pH, adsorbent amount, contact time, initial concentration of phosphate and stirring rate were optimized. Also, the isotherm models (Langmuir, Freundlich, Tamkin and Dubbin-Radshkvich) and first-order and second-order kinetics models were used to evaluate the data. The results showed that the highest removal percentage was observed at pH 5, adsorbent content of 5 g/L and contact time of 10 min at initial phosphate concentration of 10 mg/L. Using sepia powder under optimal laboratory conditions, the phosphate ion with the concentration of 10 mg/L was removed with a yield of over 99%. The results indicated that the Freundlich isotherm model gives a better description than other models showing the adsorption of phosphate ions occurs in a heterogeneous surface. Using Langmuir model, the maximum absorption capacity for phosphate was 68. 02 mg/g. The kinetic model of phosphate removal followed the pseudo-second-order model. Besides, the percentage of removal of the real samples was over 98%, indicating the great ability of this natural and inexpensive absorbent to remove this pollutant from the water solutions.

Human being encounters the lack of water as a main challenge in most parts of the world. As the world’ s population soars and welfare levels rise, the demand for water increases. Increasing demand for this limited and valuable resource is creating new strategies for freshwater management; among these are innovative techniques for wastewater treatment. One of the new methods of wastewater treatment as well as upgrading existing treatment plants is the use of packing media within the aeration tank, i. e., a Moving Bed Biofilm Reactor. In this way, a bench-scale reactor possessing a volume of 15 liters has been used and the experiments with influent COD of 500 and 1500 mg/l, media filling percentages of 30%, 50%, and 70% and hydraulic retention times of 4, 8, and 12 hours have been carried out. The observed data show that the optimum bulk density and hydraulic retention time for municipal wastewater are 50% and 4 hours and for industrial wastewater is 70% and 4 hours, respectively. Also, the kinetic study of reactor performance indicates that Grau second order model, at an acceptable level, conforms to Moving Bed Biofilm Reactor observed data. MBBR experimental results including hydraulic residence time and filling percentage data mentioned above can be utilized as reliable data in municipal and industrial wastewater treatment and afterwards reuse of treated water for irrigation.

Due to the importance of removing heavy ions from water samples, in the present study, a magnetic nanocomposite based on Fe3O4 particles coated with polyaniline was developed and evaluated as a strong adsorbent to remove lead (II) ions from water and effluent samples. In order to characterize the nanocomposite, the transmission electron microscope was used to determine the exact size of the nanoparticles and the BET technique was used to determine the effective surface of adsorbent and also the CHNS and TGA analyses were used to confirm the coating of Fe3O4 magnetic nanoparticles with polyaniline and the survey of the thermal stability of nanocomposite, respectively. The flame atomic absorption spectroscopy was used to determine the values of lead ions in the solution. Characteristics affecting lead ion removal including pH, adsorbent value and contact time at different temperatures were optimized. Optimal values of pH and adsorption rate and contact time for 100 ml of solution with an initial concentration of 50 ppm were obtained in the pH of 9, 3 mg adsorbent, and contact time of 60 minutes, respectively. Equilibrium data from adsorption studies showed that the Langmuir isotherm showed better results than the Freundlich isotherm. Also, the maximum lead adsorption capacity (II) on Polyaniline/Fe3O4 nanocomposite was 114. 9 mg of lead per gram of adsorbent.

Nitrate and phosphate are of specific importance among different water pollutants due to their effect on aquatic ecosystems and disrupting their balance. The electrocoagulation process has been recognized as a novel method that has recently been employed for the removal of nitrate and phosphate. Therefore, the present study was aimed at investigating the efficiency of simultaneous removal of nitrate and phosphate from water through an electrical coagulation process. This experimental study was performed with an experimental scale as a pilot. The pilot was made of Plexiglas with the volume of 5. 4 liters associated with a DC power supply. Parameters of the reaction time (5-90 min), pH of water (3-9), the concentration of nitrate and phosphate (1-50 mg/l), electrode materials (iron, aluminum, and steel), the distance between electrodes (1-10 cm), and the current's voltage (5-40 V) have been investigated in this research. The effect of each parameter was also examined on the amount of nitrate and phosphate removal. Obtained results were then analyzed to determine the efficiency of nitrate and phosphate removal in the form of comparable diagrams. Results of current experiments represented the optimal parameters including the reaction time of 60 min, pH of 7, initial concentration of 10 mg/l, electrodes of iron-iron, with the distance of 5 cm, and input voltage of 30 V. The removal efficiency of nitrate and phosphate under optimal condition was reported 95 and 45%, respectively, as the maximum removal rates. The present study has introduced the electrocoagulation process as a reliable and flexible way to purify water resources from nitrate and phosphate.