Environmental Engineering
M.R. Yousefi; A. Noorzad; M.J. Mahmoodi
Abstract
BACKGROUND AND OBJECTIVES: Harmful ruptures and instabilities in landfills in recent years have highlighted the importance of studying the municipal solid waste and its behavior. These instabilities mostly occur in the landfill of developing countries where waste materials are degradable and saturated. ...
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BACKGROUND AND OBJECTIVES: Harmful ruptures and instabilities in landfills in recent years have highlighted the importance of studying the municipal solid waste and its behavior. These instabilities mostly occur in the landfill of developing countries where waste materials are degradable and saturated. The behavior of waste and its ingredients are unknown as the main reasons for such instability. The main goal of this study was to better predict the behavior of landfills and unknown materials in municipal solid waste to prevent the environmental disasters.METHODS: A cylindrical specimen was modeled and subjected to triaxial test loading conditions using the finite element method. Also, fresh waste, as a waste sample with a specific composition, was investigated. Using the optimization method, the constants of the presented equation were obtained and the basic model of stress strain was presented based on composite theory.FINDINGS: The whole models for predicting the waste behavior were presented based on the behavior models of soils. This was carried out by the theory of composite materials, which was used for the first time in this study. At the strains of less than 30 percent, a well agreement was observed between the results of the numerical and the present methods. Also, at confining stresses less than 100 kiloPascal, the root mean square of the relative error percentages between the total stresses obtained from the present model and another model was less than 10 percent. At higher confining stresses, this amount was in the range of 10 – 20 percent.CONCLUSION: The results of this study were compared with those of the experimental data in previous models to verify the proposed model. The model proved to be capable of simulating and predicting the municipal solid waste behavior under various loading conditions efficiently. The results implied that assuming the municipal solid waste as composite material was reasonable and could be extended to future studies.
Environmental Management
C. Le Dinh; T. Fujiwara; M. Asari; S.T. Pham Phu
Abstract
BACKGROUND AND OBJECTIVES: Prior to the COVID-19 pandemic, Hoi An City was one of the most famous tourist destinations in the world. This led to a rapid increase in solid waste generation, leading to problems and challenges in solid waste collection and management. This problem is also being experienced ...
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BACKGROUND AND OBJECTIVES: Prior to the COVID-19 pandemic, Hoi An City was one of the most famous tourist destinations in the world. This led to a rapid increase in solid waste generation, leading to problems and challenges in solid waste collection and management. This problem is also being experienced by other developing countries of the world. Despite the existence of established waste management strategies, targets set for the collection of recyclable waste have not been met. This study introduces solutions to the problems and challenges faced by the waste management sector in Hoi An city and other developing countries. This study aimed to i) optimize the map of the recovery recycling stations in an urban community, ii) develop an effective solid waste collection system, and iii) provide management tools to enhance recycling activities, contributing to improving waste management in Hoi An city.METHODS: The RRSs were integrated into a solid waste collection system in the urban communities of Hoi An City, were conducted through location-allocation analysis in a geographic information system environment. Routing problems of carts were solved in the combination of the rescheduling of existing solid waste collection activities in the study site. The economic evaluation by scenarios was also calculated for ten years to assess the feasibility of scenarios.FINDINGS: Thirty-four locations were identified and optimized to accommodate the RRSs and new collection routes. The distances travelled and working time increased in proportion to the increase in waste separation effectiveness. Waste separation is vital to the effectiveness of the new solid waste collection system. The optimal solid waste practice model (in scenarios 2 and 4) revealed the positive results in improving the solid waste collection system, operating economy, and local adaptation.CONCLUSION: This study redesigned the solid waste collection system to solve the current problems in the tourism destination of Hoi An city. This study contributed as a case study of integrating urban recovery recycling stations into optimizing a solid waste collection system in a tourism destination. Introducing strict waste separation was the pivotal first step in systematically upgrading the solid waste collection system in Hoi An City. This study’s findings provide government officials and service providers with methods that can be applied to solve the problems faced by Hoi An city's existing solid waste collection and management system.
Environmental Science
S. Pourkarimi; A. Hallajisani; A. Alizadehdakhel; A. Nouralishahi
Abstract
BACKGROUND AND OBJECTIVES: In this study, the characteristics of bio-oil samples produced through slow pyrolysis of two different macroalgae, i.e. Azolla filiculoides and Ulva fasciata, at optimized conditions were determined and compared.METHODS: For this purpose, the effects of temperature (300-500 ...
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BACKGROUND AND OBJECTIVES: In this study, the characteristics of bio-oil samples produced through slow pyrolysis of two different macroalgae, i.e. Azolla filiculoides and Ulva fasciata, at optimized conditions were determined and compared.METHODS: For this purpose, the effects of temperature (300-500 °C), carrier gas flow rate (0.2-0.8 L/min), and heating rate (10-20 °C/min) on the final bio-oil production were optimized using response surface methodology established by a central composite design.FINDINGS: The highest bio-oil yield from U. fasciata (34.29%) was obtained at the temperature of 500 °C, nitrogen flow rate of 0.2 L/min, and heating rate of 10 °C/min. As for A. filiculoides feedstock, the highest bio-oil yield (30.83%) was achieved at the temperature of 461 °C, nitrogen flow rate of 0.5 L/min, and heating rate of 20 °C/min. Both bio-oil samples contained saturated and unsaturated hydrocarbons. However, the average hydrocarbon chain length was relatively shorter in U. fasciata bio-oil (C4-C16) than in bio-oil from A. filiculoides (C6-C24). Although both bio-oils had almost identical heating values, the U. fasciata bio-oil showed more appropriate properties, i.e. lower viscosity and density. Furthermore, the energy recovery from U. fasciata pyrolysis was calculated as 56.6% which was almost 1.5 times higher than the energy recovery from A. filiculoides pyrolysis.CONCLUSION: The results indicated that U. fasciata bio-oil, with its superior characteristics, could be proposed as a promising candidate for application in diesel-based automotive industries.
Environmental Science
M. Samimi; M. Shahriari Moghadam
Abstract
phenol and phenolic compounds are among the most recognized environmental pollutants which exist in industrial wastewater and enter the biological cycles due to the solubility in water. Bioremediation is one of the cost-effective and Eco-friendly methods for phenol removal. In this study, the most effective ...
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phenol and phenolic compounds are among the most recognized environmental pollutants which exist in industrial wastewater and enter the biological cycles due to the solubility in water. Bioremediation is one of the cost-effective and Eco-friendly methods for phenol removal. In this study, the most effective phenol-degrading bacterial strain was isolated and identified from the shores of the Oman Sea by 16S rDNA. The optimal conditions of various factors, such as pH, temperature, carbon to nitrogen ratio and salinity for the phenol biodegradation, were determined using the experimental design based on Taguchi method with L9 array (34). Ability of the isolated strain (Halomonas elongata strain O-CH1) in degradation of different phenol concentrations was analyzed. The optimum operating conditions for phenol removal were determined in pH value of 8, temperature of 35 ˚C, carbon to nitrogen ratio of 100:30 (g/L) and salinity of 35 (g/L). In these conditions, 97% of the phenol was removed from the mediums. According to the optimization results, salinity and pH were the most influential factors in the biodegradation of phenol. The O-CH1 was able to grow and degrade phenol at concentrations of 250 mg/L to 1500 mg/L. Considering the high potential of this strain for phenol degradation, determining the optimal conditions for the biodegradation and its efficacy at high concentrations of phenol, the findings in this study can be used in the biological treatment of phenolic wastewater.
M. Samimi; M. Shahriari Moghadam
Abstract
High concentrations of nitrogen compounds, such as ammonia observed in the petrochemical industry, are the major environmental pollutants. Therefore, effective and inexpensive methods are needed for its treatment. Biological treatment of various pollutants is a low cost and biocompatible replacement ...
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High concentrations of nitrogen compounds, such as ammonia observed in the petrochemical industry, are the major environmental pollutants. Therefore, effective and inexpensive methods are needed for its treatment. Biological treatment of various pollutants is a low cost and biocompatible replacement for current physico-chemical systems. The use of aquatic plants is an effective way to absorb the nutrient pollutants. In this study, the optimal operating conditions in the biological removal of ammonia from the urea-ammonia wastewater of Kermanshah Petrochemical Company by Lemna gibba were determined using the response surface methodology. Lemna gibba was collected from the ponds around Kermanshah and maintained in a nutrient medium. Effect of the main operational variables such as ammonia concentration, residence time and Lemna gibba to surface ratio on optimal conditions of ammonia removal from wastewater has been analyzed using the Box-Behnken model design of experiments. Model numerical optimization was performed to achieve the maximum amount of ammonia removal from wastewater. The ammonia removal percentage varied from 13% to 88%, but the maximum amount of ammonia removal was determined at ammonia concentration of 5 ppm and Lemna gibba residence time of 11 days in wastewater based on the quadratic model. Lemna gibba to surface ratio of 2:5 was measured at 96.449%. After optimization, validation of ammonia removal was performed under optimum conditions and measured at 92.07%. Based on the experimental design and the predicted under model conditions, the maximum amounts of ammonia removal percentage in the experiments were 82.84% and 88.33% respectively, indicating the high accuracy of the model to determine the optimum conditions for the ammonia removal from wastewater.