waste management

Technology progress is a cause of industrial hazardous wastes increasing in the whole world. Management of hazardous waste is a significant issue due to the imposed risk on environment and human life. This risk can be a result of location of undesirable facilities and also routing hazardous waste. Industrial hazardous waste management involves the collection, transportation, recycling and disposal of industrial hazardous materials that pose risk to their surroundings. The present study extends a bi-objective mathematical model in the context of industrial hazardous waste management, which covers the integrated decisions of two levels with locating and vehicle routing. Analyzing these decisions simultaneously not only may lead to the most effective structure in the waste management network, but also may reduce the potential risk of managing the hazardous waste. The problem is formulated as a bi-objective Mixed-Integer Nonlinear Programming (MINLP) model, which can be easily converted into a MILP one. In the mathematical model, three criteria are considered: minimizing total cost, which includes total transportation cost of hazardous, earliness and tardiness penalties and fixed cost of establishing centers; minimizing total transportation risk related to the population exposure along transportation routes of hazardous materials and minimizing total risk for the population around treatment and disposal centers. A DEA is applied to select the locations with high priority in CPLEX. A simulated annealing algorithm combined with an MILP solver is proposed as the solution approach. For validation of the presented method, instances with various sizes are solved. The results of the GA in small size instances, has a small deviation from the optimal fitness values. Finally, a real case study is provided to demonstrate the applicability of the model in real-world environment. Sensitivity analysis is performed to show the effect of earliness and tardiness penalty on the objective function.

With the increasing population and decreasing of earth's resources and the pollution of water, soil and air in the last few decades, environmental problems have become more visible than before. One of these problems is the excessive use of resources and excessive production of waste. Therefore, important measures have been taken in this field in recent decades, which are mostly offered in engineering and waste management. One of the important management strategies that have been implemented in this field is source reduction (reduction of produced waste in order to preserve resources and reduce waste) as the main goal and in the next stages recycling waste into the life cycle and preventing its burial through Material-energy recycling. WARM model (waste reduction model) is a tool for managers in this field, which is a road map for managers who make decisions for the future of waste management of a city or a country. This model is able to compare different management scenarios with the current situation. In this study, a proposed plan for the waste management of Tehran province for a 20-year perspective is presented in order to reduce the landfill by 30%. All input items are the default WARM model, and according to the available information and schematically, after examining several scenarios with regard to the composition of Tehran's waste and comparing them, a decision has been made about the optimal scenario.

Today, the problem of locating waste tanks and routing waste collection vehicles is closely related to the health of society and the environment. In this article, the positioning-routing problem of the periodic arc along with the intermediate discharge stations is studied under conditions of uncertainty, the purpose of which is to reduce the number of active places for waste collection in Bushehr city, to determine the optimal routes. In order to serve all the areas with the demand of the urban graph network during the week and the number of vehicles is required. A mixed integer linear programming model is developed along with taking into account the fuzzy demand to optimize the problem, and multi-objective genetic algorithm is used for the approximate solution of the problem. To evaluate the efficiency of the proposed algorithm, CPLEX solver of GAMS software is used to solve problems with small and medium dimensions. In the current research, since it is very difficult to accurately and correctly identify the distribution of parameters in the problem of waste management planning, and most of the required data have uncertainty, robust optimization approach and intuitive fuzzy approach were used to model the research problem. Is. The results of this research show that the value of the objective functions determined in the fuzzy robust method is less than the deterministic method. Among the other results of this research, we can mention a 9% reduction in the amount of use of required tanks allocated to waste collection sites, as well as a 52% reduction in active sites for waste collection.

Today, the use of plastic waste in highway and geotechnical engineering, especially in subgrade stabilization, is extensively examined. This study investigated the effect of using disposable high-density polyethylene (HDPE) chips in stabilized sandy subgrade. The impact of adding HDPE to the sand was investigated through the one-dimensional consolidation, the modified standard proctor (MSP), the California bearing ratio (CBR), and the direct shear test (DST). Adding HDPE to the sand reduced the maximum dry density of the mixture because of its low specific gravity, but the optimum moisture content did not markedly change. The incorporation of HDPE in the sand also promoted the shear strength of the mixture because of the frictional resistance and interlocking between the particles and enhanced the CBR of the sand-HDPE mixture up to 48.7%. Therefore, using HDPE chips in sand-HDPE mixtures for subgrade stabilization can significantly improve the shear strength characteristic of sandy subgrades and, thus, reduce road construction costs.

One of the most significant concerns of recent years among scientists has been related to waste management actions and policies. Unfortunately, landfills are filled with various debris and demolition from old building including waste concrete, glass, brick, ceramic, and plastic. Waste concrete seems to occupy a large volume of these landfills; thus, they are potentially among the most appropriate choices for recycling process. However, different papers have focused on the impact of recycled concrete aggregates in concrete and in recent years, no specific model has been recommended to predict the behavior of parent concrete in recycled concrete. In this study, a central composite design along with response surface methodology was employed to prepare experimental designs and model the properties of concrete made of recycled aggregates. Effective factors included compressive strength of parent concrete, substitution rate of parent concrete, and value of cement, while the compressive strength, tensile strength, and water absorption of recycled concrete were introduced as goal responses. Based on the statistical analysis, all recommended models were adequate with acceptable coefficient of determination ( ). Response surface and perturbation plots revealed that compressive strength, tensile strength, and water absorption of recycled concretes depended heavily on the compressive strength of parent concrete. Moreover, in order to generate concretes with higher compressive strength than the compressive strength of parent concrete, the value of compressive strength for parent concrete should be above MPa. However, for low-strength parent concretes, substitution rate should be limited in order to reduce undesirable performance. As the compressive strength of recycled concrete aggregates increased from to MPa, the compressive strength of recycled concrete was enhanced by over percent. In this substitution, water absorption reduced over percent. Additionally, when the compressive strength of recycled aggregates was fixed at MPa, by changing substitution rate from % to %, the compressive strength of recycled concrete increased from to MPa. The tensile strength of recycled concrete also was enhanced from to MPa.

Due to a huge increase in world energy consumption, the limited traditional fossil energy resources, and increased environmental concerns, a requirement for alternative energy sources has been paid great attention in recent years. Biodiesel is known as a nontoxic, renewable and environmental-friendly biodegradable fuel that is free from sulfur and aromatic compounds. The biodiesel production by transesterication of vegetable oils has the potential to solve the above problems and concerns. Nanocatalysts are considered as important material in chemical processes, energy production and energy savings, and prevent environmental pollution. In this study, the characteristics and performance of TiO2 nanoparticles (TNPs) and one commonly used catalyst for alkaline-catalyzed transesterication, i.e., sodium hydroxide, were evaluated using waste olive oil. The present method aords nontoxic and non-corrosive medium, high yield of biodiesel, clean reaction and simple experimental and isolation procedures. The catalyst can be recycled by simple ltration and reused without any signicant reduction in its activity. The process variables that in- uence the transesterication of triglycerides, such as volume ratio of methanol to waste olive oil, type and loading of catalyst, reaction time and reaction temperature, were investigated. High catalysis activity and a much more specic surface TNPs were found to be more superior to sodium hydroxide under the same conditions. The results showed that TNPs as catalyst can improve the biodiesel production up to 87.8% in the same condition in which the eciency is 76.4% for sodium hydroxide as a homogeneous catalyst. The eect of biodiesel/diesel blend fuels on engine exhaust emissions in a Robin engine was evaluated. The testing results show that the B20 blend fuel (including 20% and 80% v/v biodiesel and diesel fuel, respectively) reduced (HC) and carbon monoxide (CO) emissions to 28.9 and 20.6% compared to the petroleum diesel fuel, respectively. In addition, in this study, the eective use of biodiesel to reduce air pollutant emissions was approved, although a slight increase in nitrogen oxides emissions than pure diesel fuel was observed that quite what was expected due to increasing combustion temperature.