Amir Takhtravan

Bio: Amir Takhtravan is an academic researcher. The author has contributed to research in topics: Soil health & Marketing. The author has an hindex of 1, co-authored 8 publications receiving 1 citations.

Presenting a novel approach for designing chlorine contact reactors by combination of genetic algorithm with nonlinear condition functions, simulated annealing algorithm, pattern search algorithm and experimental efforts

Abstract: Nowadays, water supplies face critical conditions in terms of quality and quantity. Furthermore, growth in population along with their needs require an increasing level of water-related resources.

Assessment and sensitive analysis of biological water risks in water resources with application of classical mass transfer computations

Abstract: Due to the urgent need for water in all parts of industrial or developing societies, water supply, and transmission facilities are suitable targets for biological risks. Given that even a short interruption in water supply and water supply operations has a great impact on daily activities in the community, the deliberate contamination of urban water resources has irreparable consequences in the field of public health, and the economy of society will follow. Unfortunately, most officials in the public health control departments in our country have received limited training in detecting accidental or intentional contamination of water resources and dealing with the spread of waterborne diseases both naturally and intentionally. For this reason, there is low preparedness in the responsible agencies to deal with waterborne diseases during biological risks. In the first step of this research, a review study has been conducted on water biological risks and operational strategies to deal with them. In the following, it has studied how Escherichia coli (E. coli) bacteria spread in aqueous media. In this regard, the kinetic model of the studied microorganism was analyzed based on the implementation of (Fick Law) in polar coordinates and the combination of (Dirac Distribution) with (Legendre polynomial) distribution. Finally, after studying the factors affecting the microbial pollutant emission coefficient, the effects of all three factors of linear velocity, linear motion time period, and angle of motion on the pollutant emission flux and biofilm diffusion time in the water supply network environment were investigated. Studies have shown that the linear velocity parameter of Escherichia coli with a nonlinear relationship has the greatest effects on the release of microbial contaminants.

Enhanced Mass Transfer of CO2 into Water: Experiment and Modeling

Abstract: Concern over global warming has increased interest in quantification of the dissolution of CO2 in (sub-)- surface water. The mechanisms of the mass transfer of CO2 in aquifers and of transfer to surface water have many common features. The advantage of experiments using bulk water is that the underlying assumptions to the quantify mass-transfer rate can be validated. Dissolution of CO2 into water (or oil) increases the density of the liquid phase. This density change destabilizes the interface and enhances the transfer rate across the interface by natural convection. This paper describes a series of experiments performed in a cylindrical PVT- cell at a pressure range of pi ) 10-50 bar, where a fixed volume of CO2 gas was brought into contact with a column of distilled water. The transfer rate is inferred by following the gas pressure history. The results show that the mass-transfer rate across the interface is much faster than that predicted by Fickian diffusion and increases with increasing initial gas pressure. The theoretical interpretation of the observed effects is based on diffusion and natural convection phenomena. The CO2 concentration at the interface is estimated from the gas pressure using Henry's solubility law, in which the coefficient varies with both pressure and temperature. Good agreement between the experiments and the theoretical results has been obtained. tion of CO2 in the atmosphere, geological storage of CO2 is considered. 2-4 When CO2 is injected into an aquifer, the competition between viscous, capillary, and buoyancy forces determines the flow pattern. Eventually, due to buoyancy forces CO2 will migrate upward and be trapped under the cap rock due to capillary forces. In this case an interface between a CO2- rich phase and brine exists. Subsequently, CO2 starts to dissolve into water by molecular diffusion when it is in contact with the brine. The dissolution of CO2 increases the density of brine. 5 This density increase together with temperature fluctuations in the aquifer (which may be only partially compensated by pressure gradients 6 ) destabilize the CO2-brine interface and accelerate the transfer rate of CO2 into the brine by natural convection. 5-10 The occurrence of natural convection signifi- cantly increases the total storage rate in the aquifer since convection currents bring the fresh brine to the top. Hence, the quantification of CO2 dissolution in water and understanding the transport mechanisms are crucial in predicting the potential and long-term behavior of CO2 in aquifers. Unfortunately there are only a few experimental data in the literature, involving mass transfer between water and CO2 under elevated pressures. Weir et al. 11 were the first to point out the importance of natural convection for sequestration of CO2. Yang and Gu 8 performed experiments in bulk where a column of CO2 at high pressure was in contact with water. The procedure was similar to the established approach in which the changes in gas pressure relate the gas to the transfer rate. 12-15 A modified diffusion equation with an effective diffusivity was used to describe the mass-transfer process of CO2 into the brine. Good agreement between the experiments and the model was observed by choosing effective diffusion coefficients 2 orders of mag- nitude larger than the molecular diffusivity of CO2 into water. However, the authors pointed out that the accurate modeling of the experiments should consider natural convection effects. Farajzadeh et al. 9,10 reported experimental results for the same system, in a slightly different geometry, showing initially enhanced mass transfer followed by a classical diffusion behavior in long times. A physical model based on Fick's second law and Henry's law was used to interpret the experimental data. It was found that the mass-transfer process cannot be modeled with a modified Fick's second law with a single effective diffusion coefficient for the CO2-water system at high pressures. Nevertheless, the initial stages and later stages of the experiments can be modeled individually with the described model. Arendt et al. 16 applied a Schlieren method and a three- mode magnetic suspension balance connected to an optical cell to analyze the mass transfer of the CO2-water system up to 360 bar. Good agreement between their model (linear superposi- tion of free conVection and Marangoni convection) and the experiment was obtained. The addition of surfactant suppressed the Marangoni convection in their experiments, while in the experiments of ref 9, addition of surfactant did not have a significant effect on the transfer rate of CO2. A similar mass- transfer enhancement was observed for the mass transfer between a gaseous CO2-rich phase with two hydrocarbons (n- decane and n-hexadecane) 9,10 due to the fact that CO2 increases the hydrocarbon density. 17 The effect becomes less significant with increasing oil viscosity. This has implications for oil recovery. Indeed in geological storage of CO2 the early time behavior is governed by diffusion before the onset of the natural

Analyzing Green Construction Development Barriers by a Hybrid Decision-Making Method Based on DEMATEL and the ANP

Abstract: There is a great deal of interest in analyzing construction development barriers to identify and rank them based on sustainability criteria and have less environmental pollution. Due to the importance of construction projects in developing countries such as Iran, this study implements a green construction development paradigm to identify and rank barriers for a case study in Tehran, Iran. The main novelty of this paper is the development of a new decision-making method using the DEMATEL and Delphi techniques and the ANP. In this regard, first of all, data collection is performed through a literature review and survey studies using questionnaires, interviews, and observations. The applied method for experts’ agreement was integrated through brainstorming and the classical Delphi method. By analyzing different economic, environmental, cultural, and social criteria using a hybrid decision-making framework, the results show that the main economic barrier with a weight of 0.2607 is ranked first, while the main feature of economic assessment is connected to the risk of investment. The cultural and social barriers, with a weight of 0.2258, ranked second, and the managerial barrier, with a weight of 0.2052, ranked third. In the social and managerial aspects, the main barriers were related to looking at green construction as luxurious and the uncertainty of green construction performance due to the climate and texture of the local area, respectively. According to the findings and results, the proposed barriers and sub-barriers in this study can be used to develop and create planning at the strategic level for the development of green construction for our case study in Tehran, Iran. With a concentration on the outcomes of the present research, the sustainable green building framework can be implemented by the application of a prioritized knowledge management concept.

An efficient design of primary sedimentation tanks using a combination of the response surface, metaheuristic, and scenario building methods

Abstract: Solid particle sedimentation is assumed to be a complex procedure in water and wastewater treatment plants. There is great interest in applying and developing different simulation and optimization methods to design primary sedimentation tanks (PSTs). In traditional techniques, mechanical and physical parameters are set by sequential error loops. This study proposes a hybrid method based on the response surface methodology, efficient metaheuristics, and scenario building methods using different experimental methods to eliminate the disadvantage of existing techniques. This novel framework creates a robust and sustainable design for the PSTs. First of all, the parameters of the considered PST, based on the economic, improve process and tank efficiency scenarios are tuned and optimized by the central composition design and response surface methodology. To forecast an efficient response value for these scenarios, different metaheuristic algorithms, including the genetic algorithm (GA), pattern search algorithm (PSA), and simulate annealing algorithm, are applied. Results demonstrated that PSA, GA, and PSA with 0.02, 0.032, and 0.063 compared to experimental practices have the best calibration for predicting response in economic, improved process and tank efficiency scenarios, correspondingly. Finally, experimental tests have proven that the optimum Retention Time is equal to 2 h based on the biological oxygen demand and the total suspended solids eliminations in the laboratory-scale setup.